| { |
| "v1_col_introduction": "introduction : Magic is one of the oldest art forms, and magicians have manipulated audiences' perceptual and cognitive processes for much longer than cognitive scientists have (Martinez-Conde & Macknik 2007; Martinez-Conde & Macknik 2008; Macknik et al. 2008), Thus, classic and contemporary magic illusions provide scientists with methodological refinements and testable hypotheses about the building blocks of conscious experience (Cui et al. 2011; Otero-Millan et al. 2011). The \u201cCups and Balls\u201d is a sleight-of-hand magic trick that was performed by Roman conjurers as far back as two thousand years ago (Christopher & Christopher 2006). The trick has many variations, but the most common one uses three balls and three cups. The magician makes the balls pass through the bottom of cups, jump from cup to cup, disappear from a cup and turn up elsewhere, turn into other objects, and so on. The cups are usually opaque and the balls brightly colored. Here we examined a version of this trick inspired by a routine performed by the entertainment duo Penn & Teller, conducted with three opaque and subsequently with three transparent cups.\nMagician Teller devised this variation while fiddling with an empty water glass and wadded-up paper napkins for balls, at a Midwestern diner (Macknik, Martinez-Conde & Blakeslee 2010). He turned the glass upside down and put a ball on top, then tilted the glass so that the ball fell into his other hand. The falling ball was so compelling that it even drew his own attention away from his other hand, which was deftly and automatically loading a second ball under the glass. (He was so well practiced that he no longer needed to consciously control his hands.) In fact, Teller found that the sleight happened so quickly he himself did not realize he had loaded the transparent cup. Teller further realized that all of this took place despite the fact that he should have been able to see the secret ball as it was loaded under the cup. Its image was on his retina, but he nevertheless missed it because his attention was so enthralled with the falling ball. He surmised that if it worked for him with a transparent cup, it would work with an audience. The transparency of the cups would make the trick all the more magical to the audience. Penn & Teller claim that their version of the trick violates four rules of magic: don\u2019t tell the audience how the trick is done, don\u2019t perform the same trick twice, don\u2019t show the audience the secret preparation, and never perform cups and balls with clear plastic cups.\nHere we set up to investigate whether the falling ball in Penn & Teller's \"Cups and Balls\" generated stronger misdirection, as hypothesized by Teller, than alternative manipulations. Teller used his right hand to load (i.e. introduce surreptitiously) a small ball inside each of two upside-down cups, one at a time, while using his left hand to remove a different ball from the upside-down bottom of the cup. The third cup sleight involved one of six manipulations: a) standard maneuver (i.e. ball falling to the magicians' hand), b) standard maneuver without a third ball, c) ball placed on the table before going to the pocket, d) ball lifted before going to the pocket, e) ball dropped to the floor, and f) ball stuck to the cup. See Supplemental Movies S1-6. Seven subjects watched the videos of the performances while reporting, via button press, whenever balls were removed from the cups/table (button \u201c1\u201d) or placed inside the cups/on the table (button \u201c2\u201d).\nSubjects\u2019 perception was more accurate with transparent than with opaque cups. Perceptual performance was worse for the conditions where the ball was placed on the table, or stuck to the cup, than for the standard maneuver. The condition in which the ball was lifted displaced the\nPre Prin ts Pre Prin ts\nsubjects\u2019 gaze position the most, whereas the condition in which there was no ball caused the smallest gaze displacement. Thus, neither the \"Standard\" falling ball or the enhanced falling ball condition (where the ball fell to the floor) generated stronger misdirection, either in terms of perceptual performance or gaze position, contrary to the magician's expectation.\nTraining improved the subjects\u2019 perceptual performance. Occlusion of the magician\u2019s face did not affect the subjects\u2019 perception, suggesting that gaze misdirection does not play a strong role in the \"Cups and Balls\" illusion. Our results have implications for how to optimize the performance of this classic magic trick, and for the types of hand and object motion that maximize magic misdirection.", |
| "v2_col_introduction": "introduction : Magic is one of the oldest art forms, and magicians have manipulated audiences' perceptual and cognitive processes for much longer than cognitive scientists have (Martinez-Conde & Macknik 2007; Martinez-Conde & Macknik 2008; Macknik et al. 2008), Thus, classic and contemporary magic illusions provide scientists with methodological refinements and testable hypotheses about the building blocks of conscious experience (Cui et al. 2011; Otero-Millan et al. 2011). The \u201cCups and Balls\u201d is a sleight-of-hand magic trick that was performed by Roman conjurers as far back as two thousand years ago (Christopher & Christopher 2006). The trick has many variations, but the most common one uses three balls and three cups. The magician makes the balls pass through the bottom of cups, jump from cup to cup, disappear from a cup and turn up elsewhere, turn into other objects, and so on. The cups are usually opaque and the balls brightly colored. Here we examined a version of this trick inspired by a routine performed by the entertainment duo Penn & Teller, conducted with three opaque and subsequently with three transparent cups.\nMagician Teller devised this variation while fiddling with an empty water glass and wadded-up paper napkins for balls, at a Midwestern diner (Macknik, Martinez-Conde & Blakeslee 2010). He turned the glass upside down and put a ball on top, then tilted the glass so that the ball fell into his other hand. The falling ball was so compelling that it even drew his own attention away from his other hand, which was deftly and automatically loading a second ball under the glass. (He was so well practiced that he no longer needed to consciously control his hands.) In fact, Teller found that the sleight happened so quickly he himself did not realize he had loaded the transparent cup. Teller further realized that all of this took place despite the fact that he should have been able to see the secret ball as it was loaded under the cup. Its image was on his retina, but he nevertheless missed it because his attention was so enthralled with the falling ball. He surmised that if it worked for him with a transparent cup, it would work with an audience. The transparency of the cups would make the trick all the more magical to the audience. Penn & Teller claim that their version of the trick violates four rules of magic: don\u2019t tell the audience how the trick is done, don\u2019t perform the same trick twice, don\u2019t show the audience the secret preparation, and never perform cups and balls with clear plastic cups.\nHere we set up to investigate whether the falling ball in Penn & Teller's \"Cups and Balls\" generated stronger misdirection, as hypothesized by Teller, than alternative manipulations. Teller used his right hand to load (i.e. introduce surreptitiously) a small ball inside each of two upside-down cups, one at a time, while using his left hand to remove a different ball from the upside-down bottom of the cup. The third cup sleight involved one of six manipulations: a) standard maneuver (i.e. ball falling to the magicians' hand), b) standard maneuver without a third ball, c) ball placed on the table before going to the pocket, d) ball lifted before going to the pocket, e) ball dropped to the floor, and f) ball stuck to the cup. See Supplemental Movies S1-6. Seven subjects watched the videos of the performances while reporting, via button press, whenever balls were removed from the cups/table (button \u201c1\u201d) or placed inside the cups/on the table (button \u201c2\u201d).\nSubjects\u2019 perception was more accurate with transparent than with opaque cups. Perceptual performance was worse for the conditions where the ball was placed on the table, or stuck to the cup, than for the standard maneuver. The condition in which the ball was lifted displaced the\nPre Prin ts Pre Prin ts\nsubjects\u2019 gaze position the most, whereas the condition in which there was no ball caused the smallest gaze displacement. Thus, neither the \"Standard\" falling ball or the enhanced falling ball condition (where the ball fell to the floor) generated stronger misdirection, either in terms of perceptual performance or gaze position, contrary to the magician's expectation.\nTraining improved the subjects\u2019 perceptual performance. Occlusion of the magician\u2019s face did not affect the subjects\u2019 perception, suggesting that gaze misdirection does not play a strong role in the \"Cups and Balls\" illusion. Our results have implications for how to optimize the performance of this classic magic trick, and for the types of hand and object motion that maximize magic misdirection.", |
| "v3_col_introduction": "introduction : Magic is one of the oldest art forms, and magicians have manipulated audiences' perceptual and cognitive processes for much longer than cognitive scientists have (Martinez-Conde & Macknik 2007; Martinez-Conde & Macknik 2008; Macknik et al. 2008), Thus, classic and contemporary magic illusions provide scientists with methodological refinements and testable hypotheses about the building blocks of conscious experience (Cui et al. 2011; Otero-Millan et al. 2011). The \u201cCups and Balls\u201d is a sleight-of-hand magic trick that was performed by Roman conjurers as far back as two thousand years ago (Christopher & Christopher 2006). The trick has many variations, but the most common one uses three balls and three cups. The magician makes the balls pass through the bottom of cups, jump from cup to cup, disappear from a cup and turn up elsewhere, turn into other objects, and so on. The cups are usually opaque and the balls brightly colored. Here we examined a version of this trick inspired by a routine performed by the entertainment duo Penn & Teller, conducted with three opaque and subsequently with three transparent cups.\nMagician Teller devised this variation while fiddling with an empty water glass and wadded-up paper napkins for balls, at a Midwestern diner (Macknik, Martinez-Conde & Blakeslee 2010). He turned the glass upside down and put a ball on top, then tilted the glass so that the ball fell into his other hand. The falling ball was so compelling that it even drew his own attention away from his other hand, which was deftly and automatically loading a second ball under the glass. (He was so well practiced that he no longer needed to consciously control his hands.) In fact, Teller found that the sleight happened so quickly he himself did not realize he had loaded the transparent cup. Teller further realized that all of this took place despite the fact that he should have been able to see the secret ball as it was loaded under the cup. Its image was on his retina, but he nevertheless missed it because his attention was so enthralled with the falling ball. He surmised that if it worked for him with a transparent cup, it would work with an audience. The transparency of the cups would make the trick all the more magical to the audience. Penn & Teller claim that their version of the trick violates four rules of magic: don\u2019t tell the audience how the trick is done, don\u2019t perform the same trick twice, don\u2019t show the audience the secret preparation, and never perform cups and balls with clear plastic cups.\nHere we set up to investigate whether the falling ball in Penn & Teller's \"Cups and Balls\" generated stronger misdirection, as hypothesized by Teller, than alternative manipulations. Magician Teller used his right hand to load (i.e. introduce surreptitiously) a small ball inside each of two upside-down cups, one at a time, while using his left hand to remove a different ball from the upside-down bottom of the cup. The third cup sleight involved one of six manipulations: a) standard maneuver (i.e. ball falling to the magicians' hand), b) standard maneuver without a third ball, c) ball placed on the table before going to the pocket, d) ball lifted before going to the pocket, e) ball dropped to the floor, and f) ball stuck to the cup. Seven subjects watched the videos of the performances while reporting, via button press, whenever balls were removed from the cups/table (button \u201c1\u201d) or placed inside the cups/on the table (button \u201c2\u201d).\nSubjects\u2019 perception was more accurate with transparent than with opaque cups. Perceptual performance was worse for the conditions where the ball was placed on the table, or stuck to the cup, than for the standard maneuver. The condition in which the ball was lifted displaced the subjects\u2019 gaze position the most, whereas the condition in which there was no ball caused the\nPre Prin ts Pre Prin ts\nsmallest gaze displacement. Thus, neither the \"Standard\" falling ball or the enhanced falling ball condition (where the ball fell to the floor) generated stronger misdirection, either in terms of perceptual performance or gaze position, contrary to the magician's expectation.\nTraining improved the subjects\u2019 perceptual performance. Occlusion of the magician\u2019s face did not affect the subjects\u2019 perception, suggesting that gaze misdirection does not play a strong role in the \"Cups and Balls\" illusion. Our results have implications for how to optimize the performance of this classic magic trick, and for the types of hand and object motion that maximize magic misdirection.", |
| "v1_text": "results : Perceptual reports Subjects reported the placement and removal of balls: they pressed \u201c1\u201d whenever a ball was removed and \u201c2 whenever a new ball was placed on the table or under a cup (Figure 2; see Methods for details). We analyzed subject performance using a logistic regression model (Hosmer-Lemeshow statistic \u03c72=2.02, area under ROC curve AUC = 0.77). Subjects\u2019 performance in reporting the loading of the third cup was at chance level in the conditions with opaque cups (p > 0.05), and significantly improved in the transparent cups trials, when taking all the experimental trials into account (p < 10-7) (Figure 3A). Performance was also better for simulated rather than real loads in the opaque cups (p < 10-6), due to skipped loading reports in the opaque cups condition, which impaired perceptual performance for the real loads, but not for the simulated loads (p < 0.001) (Figure 3C). From the various sleight-of-hand maneuvers tested, the last-ball loading reports were significantly worse for the \u201cTable\u201d p<0.05) and the \u201cStuck\u201d (p < 0.05) conditions than for the \u201cStandard\u201d condition (Figure 3A). Subjects\u2019 performance was equivalent when the magician\u2019s face was visible and when it was blocked (Figure 3B). Subjects\u2019 reaction times were comparable for all three cups, across the six different sleight-of-hand manipulations (for each individual condition and for the six conditions together as a whole), and for visible vs. blocked faces. Gaze dynamics We studied the subjects\u2019 gaze dynamics during the viewing of each video clip (Figure 4; see Methods for details) using a linear regression model (R2 = 0.19). Gaze distance to the third cup was highest for the \u201cLift\u201d condition (p < 0.0001) and lowest for the \u201cNo ball\u201d condition (p < 0.0001), suggesting that the \u201cLift\u201d manipulation causes the largest gaze displacement (i.e. overt misdirection (Macknik et al. 2008)), whereas the \u201cNo ball\u201d manipulation produced the smallest gaze displacement/misdirection (possibly because in the absence of a ball, subjects may allocate stronger attention to the cup) (Figure 4A). We used a different linear regression model (R2 = 0.18) to correlate gaze distance and reaction times, we found that increased gaze distance resulted in higher reaction times (p < 0.001), with a significant effect of sleight-of-hand manipulation after controlling for the effect of gaze distance (p < 0.05). To study the potential effect of saccadic suppression on the perceptual differences we found across conditions, we estimated the saccade production rate in the same movie frames used to Pre Prin ts Pre Prin ts measure the gaze distance to the bottom of the cup (Supplemental Figure S1). Saccade production was equivalent across the tested conditions. Learning effects Subjects\u2019 performance improved over the course of the experiment (Figure 5). In the opaque cups conditions, the number of \u201clate findings\u201d (i.e. ball placement reports after the magician showed the contents of the cups) decreased with trial number (logistic regression, p < 0.01 Hosmer-Lemeshow statistic \u03c72=17.23, area under ROC curve AUC = 0.92). In the transparent cups conditions, there were few \u201clate findings\u201d, even in the initial trials (Figure 5A). In the clear cups conditions, correct loading reports for the third cup increased as the experiment progressed (logistic regression, p < 0.001, Hosmer-Lemeshow statistic \u03c72=15.02, area under ROC curve AUC = 0.73) (Figure 5B). In the opaque cup conditions, subjects did not have any information about the load of the last cup, and performed at chance, therefore we found no apparent learning effect, as expected. Reaction times decreased (linear regression, p < 0.05, R2 = 0.34) (Figure 5C) with trial number in the clear cups conditions, but remained constant in the trials with opaque cups, indicating that subjects were guessing during this condition. Gaze distance to the bottom of the third cup decreased with trial number for transparent and opaque cups (linear regression, p < 0.01, R2=0.31). To ensure that this learning effect did not affect our other conclusions about the experimental conditions, we conducted an additional analysis of subject performance as a function of the first viewing of each condition (Supplemental Figure S2). The results are comparable to those in Figure 3, indicating that the learning effect did not affect subject performance as a function of condition. Further, because the sequence of conditions was random and different for each subject, a systematic learning effect could not have biased our other results. acknowledgements : We thank the NOVA production crew for providing the filming of the videos used in the experiment, Penn & Teller from providing us with their theater and Teller for performing the magic tricks we used. methods : Subjects Seven naive subjects participated in the experiment. All participants had normal or corrected-to-normal vision, and were paid $15 dollars for a single experimental session. The experiment was carried out under the guidelines of the Barrow Neurological Institute\u2019s Internal Review Board (protocol 04BN039), and written informed consent was obtained from each participant. Eye movement recordings During the experiment, subjects rested their head on a chin/forehead-rest 57 cm away from a video monitor (Barco Reference Calibrator V), while free viewing the video clips. Their eye movements were non-invasively recorded with video-based eye tracker (Eyelink 1000, SR Research), at 500 samples per second. From the eye tracker recordings, we identified and removed blink periods as the portions of the recorded data were the pupil information was missing. Furthermore, we removed the 200 ms before and after each identified blink period, to eliminate periods of time in which the pupil is partially occluded. We identified saccades using an objective algorithm (Engbert and Kliegl 2003). To reduce spurious positives due to noise, we analyzed only binocular saccades (i.e. saccades with at least one sample of overlap in both eyes). Furthermore, we ensured that overshoot corrections were not counted as saccades by imposing a minimum intersaccadic interval of 20 ms (Otero-Millan et al. 2011). Experimental design Subjects sat in a dark, quiet room and watched video clips of 10 to 12 seconds each, in which Teller performed different variations of a \u201ccups and balls\u201d magic routine. The videos had a resolution of 720x480 pixels and subtended an area of 28x19 degrees of visual angle inside the visual field. The average luminance of the clips was 23 cd/m2, and their contrast ratio (full on/full off) was 128:1. Areas of the screen not occupied by the video were white. In each clip, Teller performed the manipulation sequentially in each of three different cups, located from left to right on the screen. The manipulation in the first two cups was identical in all the clips (Standard load, see below), whereas the routine used in the third cup varied in each video clip (Figure 1). After the third cup\u2019s sleight was complete, Teller individually lifted all Pre Prin ts Pre Prin ts three cups to show the balls hidden underneath them. Subjects were instructed to report, as fast as possible, the removal and placing of each ball as soon as they were aware of them, by pressing one of two different buttons on a gamepad with their left and right index fingers (button \u201c1\u201d for removals, button \u201d2\u201d for placings, see Figure 2). A removal was defined as the moment each ball stopped touching either the table or a cup, and a placing was defined as when each ball made physical contact with a cup or the table. The different routines tested were: a) Standard (Supplemental Movie S1): the standard maneuver, identical to the one performed in the first two cups b) No ball (Supplemental Movie S2): similar to the \u201cStandard\u201d routine, but there was no ball on top of the third cup c) Lift (Supplemental Movie S3): the ball on top of the third cup was lifted to eye level before loading the cup d) Table (Supplemental Movie S4): the top ball on the third cup was placed on the table before the cup was loaded e) Drop (Supplemental Movie S5): the top ball on the third cup was dropped to the floor before the cup was loaded f) Stuck (Supplemental Movie S6): similar to the \u201cDrop\u201d condition, but the ball was stuck to the cup and therefore it did not fall. For each of these different routines, we tested other variables concerning the magician\u2019s performance. We tested \u201cClear Cups\u201d, in which the cups were transparent, versus \u201cOpaque Cups\u201d, in which the cups were not. We also tested \u201cLoad\u201d versus \u201cNo load\u201d conditions, in which the third cup was either \u201cloaded\u201d (i.e. a ball was surreptitiously placed under it), or not. Finally, we compared a \u201cNo face\u201d condition, in which the magician\u2019s face was occluded by a static black rectangle, versus the unmodified \u201cFace\u201d-visible video clips. This yielded a total of 48 conditions. Each subject saw each condition twice. The order of conditions was blocked and randomized for each subject. Each participant saw all the 48 conditions first in random order, and then the same conditions again in a new random sequence. Data analysis We defined a correct report of ball placement or removal as an appropriate button press in the 2000 ms immediately following the first movie frame in a movie in which the ball had been placed or removed. We also coded correct reports when subject did not indicate a placement after the magician performed a faked load. The reaction time of each report was measured in the conditions in which the cup was loaded. For each placing, gaze distance and saccade rate was calculated as the average distance between the subjects\u2019 gaze and the point where the cup sat on the table, during the 400 ms immediately subsequent to, and following, the first movie frame in which the load occurs (or the equivalent frame in the \u201cNo load\u201d condition). We varied the duration of these two time windows and found that the results were similar. Subjects were allowed to report ball placings during the reveal sequence at the end of each trial, in which the magician lifted the cups to show their contents. We counted the number of reports the subjects made during this period in each trial and considered them \u201clate findings\u201d. Pre Prin ts Pre Prin ts Statistical testing employed a logistic regression fit to correct reports of placings and removals, and a linear regression fit to the reaction times and the gaze distances. The different magic routines, the load or no load of the third cup, the visibility or occlusion of the face, and the clear or opaque cups were factors in the main analyses. The analyses to determine the evolution of responses and gaze positions throughout the experiment used only the trial number as predictor. The statistical models determined main effects and first order interactions, when applicable. Only significant effects are reported in the text. Pairwise comparisons across different routines were tested with the Newman-Keuls post hoc test. discussion : We investigated the potential contribution of several perceptual elements in Penn & Teller's version of the classic \"Cups and balls\" magic trick. We measured the perceptual performance and gaze behavior of naive observers as Teller surreptitiously introduced balls inside opaque and transparent upside down plastic cups. Contrary to the magician's intuition, a gravity-driven drop of a ball into his hand (or to the floor) caused less misdirection, both in terms of gaze displacement and impaired perception, than alternative manipulations such as lifting the ball, or placing it on the table. Thus, perception of (the effects of gravity on) falling objects does not enhance magic misdirection, at least in the performance of this particular sleight-of-hand trick. The contradiction between our results and the magician\u2019s original perception may have been caused by one or more of several possible sources. One possibility is that performing the trick in a new way may have drawn his attention towards the new element (the ball dropping), and away from the common element (the loading of the cup). Successive, non-controlled repetitions of the procedure could have given the impression of a worse detection of the loading because of confirmation bias. Our results confirm that controlled experiments give valuable insight to reject (Cui et al. 2011) or accept (Otero-Millan et al. 2011) intuitive judgments about attention and misdirection formulated by the magicians. Further, the three consecutive sleight-of-hand Pre Prin ts Pre Prin ts manipulations (actual or simulated loads) were presented in isolation, rather than as part of a complete \"Cups and balls\" magic routine (an arrangement of tricks organized in logical fashion as part of a magic performance). Finally, because an actual magician (i.e. rather than a cartoon or computer simulation) performed all maneuvers, motion features such as timing, duration, etc. could not be exactly equated across all experimental conditions. Future research using computer simulations of the magician\u2019s sleight-of-hand movements should conducted with the goal of replicating and generalizing the current findings to other sleights-of-hand and magic tricks. Blocking or unblocking the magician's face did not affect the observers' perception or oculomotor behavior, suggesting that the \"Cups and balls\" magic trick does not rely on social misdirection (for instance, due to the magician's head or eye position/movements). These results are surprising\u2014the belief among magician's that social misdirection, generated by the face, is one of their most powerful tools, is pervasive\u2014though they agree with those reported by Cui et al (Cui et al. 2011) with a different magic trick. Together they suggest that different magic illusions may differentially be enhanced, unchanged or lessened by social misdirection. Also in agreement with Cui et al's research (Cui et al. 2011), we found significant effects of learning on the perception and gaze behavior or initially naive observers--the more spectators see a trick the less effective the misdirection. Our combined results have implications for how to optimize the performance of the \"Cups and balls\" magic trick, and for the types of hand and object motion that maximize magic misdirection. in \u201cstandard\u201d, the routine performed on the third cup was identical to that performed for the previous : two cups. In \u201cNo ball\u201d, the routine was again the same as in the first two cups, but there was no ball initially placed on top of the cup. In \u201clift\u201d, the ball initially on top of the third cup was lifted to approximately eye level before the cup was loaded. In \u201cTable\u201d, the ball originally on top of the third cup was placed on the table before the cup was loaded. In \u201cDrop\u201d, the ball was dropped out of the screen before the third cup was loaded. In \u201cStuck\u201d, the ball was attached to the top of the third cup but the magician follows it with his gaze as in the \u201cDrop\u201d condition. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 2 example trial : Schematic of a single trial for the standard routine in which the third cup is loaded. The spikes in the time courses show when a load or removal happens (dashed lines) or is reported (solid lines). Blue color symbolizes the removals of balls, and red color indicates the loadings. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 3 Summary of subjects\u2019 performance across the different conditions a) Subjects performance in reporting the load of the third cup across the different routines, for the conditions with clear and opaque cups. Performance is uniform across the different routines for the opaque cups, and worse than in the conditions with clear cups (logistic regression, p < 10-7). When the cups are clear, and the loading or no loading of the cup is therefore visible, performance is worse for the \u201cTable\u201d and \u201cStuck\u201d routines (logistic regression, p < 0.05). b) Performance was similar regardless of the face being visible or not. c) Performance was better for the \u201cNo load\u201d condition with opaque cups (logistic regression, p < 0.001). Dashed lines show the expected chance performance level. Error bars indicate the standard error from the mean across subjects.Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 4 Gaze displacement from the bottom of the cup at the time the cup is being loaded a) Gaze distance across the different routines. The \u201cLift\u201d routine causes the biggest displacement from the bottom of the cup (linear regression, p <0.0001), while the \u201cNo ball\u201d routine produces the smallest one (linear regression, p < 0.0001). b) Gaze displacement was similar for the \u201cClear Cups\u201d and \u201cOpaque Cups\u201d conditions. c) Gaze displacement was similar for the \u201cFace\u201d and \u201cNo face\u201d conditions. Distance is reported in units of degrees of visual angle, and error bars indicate the standard error from the mean across subjects. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 5 Effects of learning in perceptual reports and gaze distance a)The number of late findings (placings reported after the magician shows what is under the cups) goes down with the trial number in the conditions with the opaque cups, while is very low during the experiment for the conditions with clear cups. The correlation between the trial number and the number of late findings is statistically significant in the conditions with opaque cups (logistic regression, p < 0.01). b) Probability of subjects reporting correctly the loading of the third cup in the conditions with clear cups as a function of the trial number. The relationship is statistically significant (logistic regression, p < 0.001). c) The reaction times of the subjects reporting the loading of the third cup (in the conditions with clear cups) decreased with the number of trials (linear regression, p < 0.05). d) Similarly, the gaze distance (in degrees of visual angle) to the bottom of the cup decreased with the trial number (linear regression, p < 0.01). Error bars indicate standard error from the mean across subjects. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts", |
| "v2_text": "results : Perceptual reports Subjects reported the placement and removal of balls: they pressed \u201c1\u201d whenever a ball was removed and \u201c2 whenever a new ball was placed on the table or under a cup (Figure 2; see Methods for details). Subjects\u2019 performance in reporting the loading of the third cup was at chance level in the conditions with opaque cups (logistic regression, p > 0.05, Hosmer-Lemeshow statistic \u03c72=2.02, area under ROC curve AUC = 0.77), and significantly improved in the transparent cups trials, when taking all the experimental trials into account (logistic regression, p < 10-7, Hosmer-Lemeshow statistic \u03c72=2.02, area under ROC curve AUC = 0.77) (Figure 3A). Performance was also better for simulated rather than real loads in the opaque cups (logistic regression, p < 10-6, Hosmer-Lemeshow statistic \u03c72=2.02, area under ROC curve AUC = 0.77), due to skipped loading reports in the opaque cups condition, which impaired perceptual performance for the real loads, but not for the simulated loads (logistic regression, p < 0.001, Hosmer-Lemeshow statistic \u03c72=2.02, area under ROC curve AUC = 0.77) (Figure 3C). From the various sleight-of-hand maneuvers tested, the last-ball loading reports were significantly worse for the \u201cTable\u201d (logistic regression, p<0.05, Hosmer-Lemeshow statistic \u03c72=2.02, area under ROC curve AUC = 0.77) and the \u201cStuck\u201d (logistic regression, p < 0.05, Hosmer-Lemeshow statistic \u03c72=2.02, area under ROC curve AUC = 0.77) conditions than for the \u201cStandard\u201d condition (Figure 3A). Subjects\u2019 performance was equivalent when the magician\u2019s face was visible and when it was blocked (Figure 3B). Subjects\u2019 reaction times were comparable for all three cups, across the six different sleight-of-hand manipulations (for each individual condition and for the six conditions together as a whole), and for visible vs. blocked faces. Gaze dynamics We studied the subjects\u2019 gaze dynamics during the viewing of each video clip (Figure 4; see Methods for details). Gaze distance to the third cup was highest for the \u201cLift\u201d condition (linear regression, p < 0.0001, R2 = 0.19) and lowest for the \u201cNo ball\u201d condition (linear regression, p < 0.0001, R2 = 0.19), suggesting that the \u201cLift\u201d manipulation causes the largest gaze displacement (i.e. overt misdirection (Macknik et al. 2008)), whereas the \u201cNo ball\u201d manipulation produced the smallest gaze displacement/misdirection (possibly because in the absence of a ball, subjects may allocate stronger attention to the cup) (Figure 4A). Increased gaze distance resulted in higher reaction times (linear regression, p < 0.001, R2 = 0.18), with a significant effect of sleight-of-hand manipulation after controlling for the effect of gaze distance (linear regression, p < 0.05, R2 = 0.18). Pre Prin ts Pre Prin ts To study the potential effect of saccadic suppression on the perceptual differences we found across conditions, we estimated the saccade production rate in the same movie frames used to measure the gaze distance to the bottom of the cup (Supplemental Figure S1). Saccade production was equivalent across the tested conditions. Learning effects Subjects\u2019 performance improved over the course of the experiment (Figure 5). In the opaque cups conditions, the number of \u201clate findings\u201d (i.e. ball placement reports after the magician showed the contents of the cups) decreased with trial number (logistic regression, p < 0.01 Hosmer-Lemeshow statistic \u03c72=17.23, area under ROC curve AUC = 0.92). In the transparent cups conditions, there were few \u201clate findings\u201d, even in the initial trials (Figure 5A). In the clear cups conditions, correct loading reports for the third cup increased as the experiment progressed (logistic regression, p < 0.001, Hosmer-Lemeshow statistic \u03c72=15.02, area under ROC curve AUC = 0.73) (Figure 5B). In the opaque cup conditions, subjects did not have any information about the load of the last cup, and performed at chance, therefore we found no apparent learning effect, as expected. Reaction times decreased (linear regression, p < 0.05, R2 = 0.34) (Figure 5C) with trial number in the clear cups conditions, but remained constant in the trials with opaque cups, indicating that subjects were guessing during this condition. Gaze distance to the bottom of the third cup decreased with trial number for transparent and opaque cups (linear regression, p < 0.01, R2=0.31). To ensure that this learning effect did not affect our other conclusions about the experimental conditions, we conducted an additional analysis of subject performance as a function of the first viewing of each condition (Supplemental Figure S2). The results are comparable to those in Figure 3, indicating that the learning effect did not affect subject performance as a function of condition. Further, because the sequence of conditions was random and different for each subject, a systematic learning effect could not have biased our other results. acknowledgements : We thank the NOVA production crew for providing the filming of the videos used in the experiment, Penn & Teller from providing us with their theater and Teller for performing the magic tricks we used. discussion : We investigated the potential contribution of several perceptual elements in Penn & Teller's version of the classic \"Cups and balls\" magic trick. We measured the perceptual performance and gaze behavior of naive observers as Teller surreptitiously introduced balls inside opaque and transparent upside down plastic cups. Contrary to the magician's intuition, a gravity-driven drop of a ball into his hand (or to the floor) caused less misdirection, both in terms of gaze displacement and impaired perception, than alternative manipulations such as lifting the ball, or placing it on the table. Thus, perception of (the effects of gravity on) falling objects does not enhance magic misdirection, at least in the performance of this particular sleight-of-hand trick. The contradiction between our results and the magician\u2019s original perception may have been caused by one or more of several possible sources. One possibility is that performing the trick in a new way may have drawn his attention towards the new element (the ball dropping), and away from the common element (the loading of the cup). Successive, non-controlled repetitions of the procedure could have given the impression of a worse detection of the loading because of Pre Prin ts Pre Prin ts confirmation bias. Our results confirm that controlled experiments give valuable insight to reject (Cui et al. 2011) or accept (Otero-Millan et al. 2011) intuitive judgments about attention and misdirection formulated by the magicians. Further, the three consecutive sleight-of-hand manipulations (actual or simulated loads) were presented in isolation, rather than as part of a complete \"Cups and balls\" magic routine (an arrangement of tricks organized in logical fashion as part of a magic performance). Finally, because an actual magician (i.e. rather than a cartoon or computer simulation) performed all maneuvers, motion features such as timing, duration, etc. could not be exactly equated across all experimental conditions. Future research using computer simulations of the magician\u2019s sleight-of-hand movements should conducted with the goal of replicating and generalizing the current findings to other sleights-of-hand and magic tricks. Blocking or unblocking the magician's face did not affect the observers' perception or oculomotor behavior, suggesting that the \"Cups and balls\" magic trick does not rely on social misdirection (for instance, due to the magician's head or eye position/movements). These results are surprising\u2014the belief among magician's that social misdirection, generated by the face, is one of their most powerful tools, is pervasive\u2014though they agree with those reported by Cui et al (Cui et al. 2011) with a different magic trick. Together they suggest that different magic illusions may differentially be enhanced, unchanged or lessened by social misdirection. Also in agreement with Cui et al's research (Cui et al. 2011), we found significant effects of learning on the perception and gaze behavior or initially naive observers--the more spectators see a trick the less effective the misdirection. Our combined results have implications for how to optimize the performance of the \"Cups and balls\" magic trick, and for the types of hand and object motion that maximize magic misdirection. in \u201cstandard\u201d, the routine performed on the third cup was identical to that performed for the previous : two cups. In \u201cNo ball\u201d, the routine was again the same as in the first two cups, but there was no ball initially placed on top of the cup. In \u201clift\u201d, the ball initially on top of the third cup was lifted to approximately eye level before the cup was loaded. In \u201cTable\u201d, the ball originally on top of the third cup was placed on the table before the cup was loaded. In \u201cDrop\u201d, the ball was dropped out of the screen before the third cup was loaded. In \u201cStuck\u201d, the ball was attached to the top of the third cup but the magician follows it with his gaze as in the \u201cDrop\u201d condition. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 2 methods : Subjects Seven naive subjects participated in the experiment. All participants had normal or corrected-to-normal vision, and were paid $15 dollars for a single experimental session. The experiment was carried out under the guidelines of the Barrow Neurological Institute\u2019s Internal Review Board (protocol 04BN039), and written informed consent was obtained from each participant. Eye movement recordings During the experiment, subjects rested their head on a chin/forehead-rest 57 cm away from a video monitor (Barco Reference Calibrator V), while free viewing the video clips. Their eye movements were non-invasively recorded with video-based eye tracker (Eyelink 1000, SR Research), at 500 samples per second. From the eye tracker recordings, we identified and removed blink periods as the portions of the recorded data were the pupil information was missing. Furthermore, we removed the 200 ms before and after each identified blink period, to eliminate periods of time in which the pupil is partially occluded. We identified saccades using an objective algorithm (Engbert and Kliegl 2003). To reduce spurious positives due to noise, we analyzed only binocular saccades (i.e. saccades with at least one sample of overlap in both eyes). Furthermore, we ensured that overshoot corrections were not counted as saccades by imposing a minimum intersaccadic interval of 20 ms (Otero-Millan et al. 2011). Experimental design Subjects sat in a dark, quiet room and watched video clips of 10 to 12 seconds each, in which Teller performed different variations of a \u201ccups and balls\u201d magic routine. The videos had a resolution of 720x480 pixels and subtended an area of 28x19 degrees of visual angle inside the visual field. The average luminance of the clips was 23 cd/m2, and their contrast ratio (full on/full off) was 128:1. Areas of the screen not occupied by the video were white. In each clip, Teller performed the manipulation sequentially in each of three different cups, located from left to right on the screen. The manipulation in the first two cups was identical in all the clips (Standard load, see below), whereas the routine used in the third cup varied in each video clip (Figure 1). After the third cup\u2019s sleight was complete, Teller individually lifted all Pre Prin ts Pre Prin ts three cups to show the balls hidden underneath them. Subjects were instructed to report, as fast as possible, the removal and placing of each ball as soon as they were aware of them, by pressing one of two different buttons on a gamepad with their left and right index fingers (button \u201c1\u201d for removals, button \u201d2\u201d for placings, see Figure 2). A removal was defined as the moment each ball stopped touching either the table or a cup, and a placing was defined as when each ball made physical contact with a cup or the table. The different routines tested were: a) Standard (Supplemental Movie S1): the standard maneuver, identical to the one performed in the first two cups b) No ball (Supplemental Movie S2): similar to the \u201cStandard\u201d routine, but there was no ball on top of the third cup c) Lift (Supplemental Movie S3): the ball on top of the third cup was lifted to eye level before loading the cup d) Table (Supplemental Movie S4): the top ball on the third cup was placed on the table before the cup was loaded e) Drop (Supplemental Movie S5): the top ball on the third cup was dropped to the floor before the cup was loaded f) Stuck (Supplemental Movie S6): similar to the \u201cDrop\u201d condition, but the ball was stuck to the cup and therefore it did not fall. For each of these different routines, we tested other variables concerning the magician\u2019s performance. We tested \u201cClear Cups\u201d, in which the cups were transparent, versus \u201cOpaque Cups\u201d, in which the cups were not. We also tested \u201cLoad\u201d versus \u201cNo load\u201d conditions, in which the third cup was either \u201cloaded\u201d (i.e. a ball was surreptitiously placed under it), or not. Finally, we compared a \u201cNo face\u201d condition, in which the magician\u2019s face was occluded by a static black rectangle, versus the unmodified \u201cFace\u201d-visible video clips. This yielded a total of 48 conditions. Each subject saw each condition twice. The order of conditions was blocked and randomized for each subject. Each participant saw all the 48 conditions first in random order, and then the same conditions again in a new random sequence. Data analysis We defined a correct report of ball placement or removal as an appropriate button press in the 2000 ms immediately following the first movie frame in a movie in which the ball had been placed or removed. We also coded correct reports when subject did not indicate a placement after the magician performed a faked load. The reaction time of each report was measured in the conditions in which the cup was loaded. For each placing, gaze distance and saccade rate was calculated as the average distance between the subjects\u2019 gaze and the point where the cup sat on the table, during the 400 ms immediately subsequent to, and following, the first movie frame in which the load occurs (or the equivalent frame in the \u201cNo load\u201d condition). We varied the duration of these two time windows and found that the results were similar. Subjects were allowed to report ball placings during the reveal sequence at the end of each trial, in which the magician lifted the cups to show their contents. We counted the number of reports the subjects made during this period in each trial and considered them \u201clate findings\u201d. Pre Prin ts Pre Prin ts Statistical testing employed a logistic regression fit to correct reports of placings and removals, and a linear regression fit to the reaction times and the gaze distances. The different magic routines, the load or no load of the third cup, the visibility or occlusion of the face, and the clear or opaque cups were factors in the main analyses. The analyses to determine the evolution of responses and gaze positions throughout the experiment used only the trial number as predictor. The statistical models determined main effects and first order interactions, when applicable. Only significant effects are reported in the text. Pairwise comparisons across different routines were tested with the Newman-Keuls post hoc test. example trial : Schematic of a single trial for the standard routine in which the third cup is loaded. The spikes in the time courses show when a load or removal happens (dashed lines) or is reported (solid lines). Blue color symbolizes the removals of balls, and red color indicates the loadings. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 3 Summary of subjects\u2019 performance across the different conditions a) Subjects performance in reporting the load of the third cup across the different routines, for the conditions with clear and opaque cups. Performance is uniform across the different routines for the opaque cups, and worse than in the conditions with clear cups (logistic regression, p < 10-7). When the cups are clear, and the loading or no loading of the cup is therefore visible, performance is worse for the \u201cTable\u201d and \u201cStuck\u201d routines (logistic regression, p < 0.05). b) Performance was similar regardless of the face being visible or not. c) Performance was better for the \u201cNo load\u201d condition with opaque cups (logistic regression, p < 0.001). Dashed lines show the expected chance performance level. Error bars indicate the standard error from the mean across subjects.Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 4 Gaze displacement from the bottom of the cup at the time the cup is being loaded a) Gaze distance across the different routines. The \u201cLift\u201d routine causes the biggest displacement from the bottom of the cup (linear regression, p <0.0001), while the \u201cNo ball\u201d routine produces the smallest one (linear regression, p < 0.0001). b) Gaze displacement was similar for the \u201cClear Cups\u201d and \u201cOpaque Cups\u201d conditions. c) Gaze displacement was similar for the \u201cFace\u201d and \u201cNo face\u201d conditions. Distance is reported in units of degrees of visual angle, and error bars indicate the standard error from the mean across subjects. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 5 Effects of learning in perceptual reports and gaze distance a)The number of late findings (placings reported after the magician shows what is under the cups) goes down with the trial number in the conditions with the opaque cups, while is very low during the experiment for the conditions with clear cups. The correlation between the trial number and the number of late findings is statistically significant in the conditions with opaque cups (logistic regression, p < 0.01). b) Probability of subjects reporting correctly the loading of the third cup in the conditions with clear cups as a function of the trial number. The relationship is statistically significant (logistic regression, p < 0.001). c) The reaction times of the subjects reporting the loading of the third cup (in the conditions with clear cups) decreased with the number of trials (linear regression, p < 0.05). d) Similarly, the gaze distance (in degrees of visual angle) to the bottom of the cup decreased with the trial number (linear regression, p < 0.01). Error bars indicate standard error from the mean across subjects. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts", |
| "v3_text": "methods : Subjects Seven naive subjects participated in the experiment. All participants had normal or corrected-to-normal vision, and were paid $15 dollars for a single experimental session. The experiment was carried out under the guidelines of the Barrow Neurological Institute\u2019s Internal Review Board (protocol 04BN039), and written informed consent was obtained from each participant. Eye movement recordings During the experiment, subjects rested their head on a chin/forehead-rest 57 cm away from a video monitor (Barco Reference Calibrator V), while their eye movements were non-invasively recorded with video-based eye tracker (Eyelink 1000, SR Research), at 500 samples per second. From the eye tracker recordings, we identified and removed blink periods as the portions of the recorded data were the pupil information was missing. Furthermore, we removed the 200 ms before and after each identified blink period, to eliminate periods of time in which the pupil is partially occluded. Experimental design Subjects were presented with video clips in which a magician performed different variations of a \u201ccups and balls\u201d routine. In each clip, the magician performed the manipulation sequentially in each of three different cups, located from left to right on the screen. The manipulation in the first two cups was identical in all the clips (the Standard load, see below), whereas the routine used in the third cup varied in each video clip (Figure 1). After the third cup\u2019s sleight was complete, the magician individually lifted all three of the cups to show the balls hidden underneath them. Subjects reported the removal and placing of each ball as soon as they were aware of them, by pressing one of two different buttons on a gamepad (button \u201c1\u201d for removals, button \u201d2\u201d for placings). A removal was defined as the moment each ball stopped touching either the table or a cup, and a placing was defined as when each ball made physical contact with a cup or the table. The different routines tested were: a) Standard: the standard maneuver, identical to the one performed in the first two cups b) No ball: similar to the \u201cStandard\u201d routine, but there was no ball on top of the third cup c) Lift: the ball on top of the third cup was lifted to eye level before loading the cup d) Table: the top ball on the third cup was placed on the table before the cup was loaded e) Drop: the top ball on the third cup was dropped to the floor before the cup was loaded Pre Prin ts Pre Prin ts f) Stuck: similar to the \u201cDrop\u201d condition, but the ball was stuck to the cup and therefore it did not fall. For each of these different routines, we tested other variables concerning the magician\u2019s performance. We tested \u201cClear Cups\u201d , in which the cups were transparent, versus \u201cOpaque Cups\u201d, in which the cups were not. We also tested \u201cLoad\u201d versus \u201cNo load\u201d conditions, in which the third cup was either \u201cloaded\u201d (i.e. a ball was surreptitiously placed under it), or not. Finally, we compared a \u201cNo face\u201d condition, in which the magician\u2019s face was occluded by a static black rectangle, versus the unmodified \u201cFace\u201d-visible video clips. This yielded a total of 48 conditions. Each subject saw each condition twice. Data analysis We defined a correct report of ball placement or removal as an appropriate button press in the 2000 ms immediately following the first movie frame in a movie in which the ball had been placed our removed. We also coded correct reports when subject did not indicate a placement after the magician performed a faked load. The reaction time of each report was measured in the conditions in which the cup was loaded. For each placing, the gaze distance was calculated as the average distance between the subjects\u2019 gaze and the point where the cup sat on the table, during the 400 ms immediately subsequent to, and following, the first movie frame in which the load occurs (or the equivalent frame in the \u201cNo load\u201d condition). We varied the duration of these two time windows and found that the results were similar. Subject reports were considered late if they occurred after the magician lifted the three cups in the reveal sequence at the end of the trick. Statistical testing employed a logistic regression fit to correct reports of placings and removals, and a linear regression fit to the reaction times and the gaze distances. The statistical models determined main effects and first order interactions, when applicable. Pairwise comparisons across different routines were tested using the Newman-Keuls post hoc test. results : Perceptual reports Subjects reported the place and removal of balls: they pressed \u201c1\u201d whenever a ball was removed and \u201c2 whenever a new ball was placed on the table or under a cup (Figure 2; see Methods for details). Performance was significantly better for transparent than for opaque cups (logistic regression, p < 10-7) (Figure 2A), as well as for simulated rather than real loads in the opaque cups (logistic regression, p<10-6) (Figure 2C). From the various sleight-of-hand maneuvers tested, performance was significantly worse for the \u201cTable\u201d (logistic regression, p<0.05) and the \u201cStuck\u201d (logistic regression, p<0.05) conditions than for the \u201cStandard\u201d condition (Figure 2A). Subjects\u2019 performance was equivalent when the magician\u2019s face was visible and when it was blocked (Figure 2B). Subjects\u2019 reaction times were comparable for all three cups, across the six different sleight-of-hand manipulations (for each individual condition and for the six conditions together as a whole), and for visible vs. blocked faces (linear regression, p > 0.05). Pre Prin ts Pre Prin ts Gaze dynamics We studied the subjects\u2019 gaze dynamics during the viewing of each video clip (Figure 3; see Methods for details). Gaze distance to the third cup was highest for the \u201cLift\u201d condition (linear regression, p < 0.0001) and lowest for the \u201cNo ball\u201d condition (linear regression, p < 0.0001), suggesting that the \u201cLift\u201d manipulation causes the largest gaze displacement (i.e. overt misdirection (Macknik et al. 2008)), whereas the \u201cNo ball\u201d manipulation produced the smallest gaze displacement/misdirection (possibly because in the absence of a ball, subjects may allocate stronger attention to the cup) (Figure 3A). Increased gaze distance resulted in higher reaction times (linear regression, p<0.001), with a significant effect of sleight-of-hand manipulation after controlling for the effect of gaze distance (linear regression, p<0.05). Learning effects Subjects\u2019 performance improved over the course of the experiment (Figure 4). In the opaque cups conditions, the number of \u201clate findings\u201d (i.e. ball placement reports after the magician showed the contents of the cups) decreased with trial number (logistic regression, p < 0.01). In the transparent cups conditions, there were few \u201clate findings\u201d, even in the initial trials (Figure 4A). In the clear cups conditions, correct loading reports for the third cup increased (logistic regression, p < 0.001) (Figure 4B) and reaction times decreased (linear regression, p < 0.05) (Figure 4C) with trial number. The effects of learning on reaction times and correct loading reports were less clear in the opaque cups conditions. Gaze distance to the bottom of the third cup decreased with trial number for transparent and opaque cups (linear regression, p < 0.01). discussion : Here we investigated the potential participation of several perceptual elements in professional magicians Penn & Teller's version of the classic \"Cups and balls\" magic trick. We measured the perceptual performance and gaze behavior of naive observers as magician Teller surreptitiously introduced balls inside opaque and transparent upside down plastic cups. Contrary to the magician's intuition, a gravity-driven drop of a ball into his hand (or to the floor) caused less misdirection, both in terms of gaze displacement and impaired perception, than alternative manipulations such as lifting the ball, or placing it on the table. Thus, perception of (the effects of gravity on) falling objects does not enhance magic misdirection, at least in the performance of this particular sleight-of-hand trick. Two experimental factors potentially limit the power of these conclusions. First, the three consecutive sleight-of-hand manipulations (actual or simulated loads) were presented in isolation, rather than as part of a complete \"Cups and balls\" magic routine (an arrangement of tricks organized in logical fashion as part of a magic performance). Second, because an actual magician (i.e. rather than a cartoon or computer simulation) performed all maneuvers, motion features such as timing, duration, etc. could not be exactly equated across all experimental conditions. Future research using computer simulations of the magician\u2019s sleight-of-hand movements should conducted with the goal of replicating and generalizing the current findings to other sleights-of-hand and magic tricks. Pre Prin ts Pre Prin ts Blocking or unblocking the magician's face did not affect the observers' perception or oculomotor behavior, suggesting that the \"Cups and balls\" magic trick does not rely on social misdirection (for instance, due to the magician's head or eye position/movements). These results are surprising--the belief among magician's that social misdirection, generated by the face, is one of their most powerful tools, is pervasive--though they agree with those reported by Cui et al (Cui et al. 2011) with a different magic trick. Together they suggest that different magic illusions may differentially be enhanced, unchanged or lessened by social misdirection. Also in agreement with Cui et al's research (Cui et al. 2011), we found significant effects of learning on the perception and gaze behavior or initially naive observers--the more spectators see a trick the less effective the misdirection. Our combined results have implications for how to optimize the performance of the \"Cups and balls\" magic trick, and for the types of hand and object motion that maximize magic misdirection. acknowledgements : We thank the NOVA production crew for providing the filming of the videos used in the experiment, Penn & Teller from providing us with their theater and Teller for performing the magic tricks we used. in \u201cstandard\u201d, the routine performed on the third cup was identical to that performed for the previous : two cups. In \u201cNo ball\u201d, the routine was again the same as in the first two cups, but there was no ball initially placed on top of the cup. In \u201clift\u201d, the ball initially on top of the third cup was lifted to approximately eye level before the cup was loaded. In \u201cTable\u201d, the ball originally on top of the third cup was placed on the table before the cup was loaded. In \u201cDrop\u201d, the ball was dropped out of the screen before the third cup was loaded. In \u201cStuck\u201d, the ball was attached to the top of the third cup but the magician follows it with his gaze as in the \u201cDrop\u201d condition. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 2 Summary of the different routines tested in the experiment Summary of subjects\u2019 performance across the different conditions two cups. In \u201cNo ball\u201d, the routine was again the same as in the first two cups, but there was no ball initially placed on top of the cup. In \u201clift\u201d, the ball initially on top of the third cup was lifted to approximately eye level before the cup was loaded. In \u201cTable\u201d, the ball originally on top of the third cup was placed on the table before the cup was loaded. In \u201cDrop\u201d, the ball was dropped out of the screen before the third cup was loaded. In \u201cStuck\u201d, the ball was attached to the top of the third cup but the magician follows it with his gaze as in the \u201cDrop\u201d condition. a) Subjects performance across the different routines, for the conditions with clear and opaque cups. Performance is uniform across the different routines for the opaque cups, and worse than in the conditions with clear cups (logistic regression, p < 10-7). When the cups are clear, and the loading or no loading of the cup is therefore visible, performance is worse for the \u201cTable\u201d and \u201cStuck\u201d routines (logistic regression, p < 0.05). b) Performance was similar regardless of the face being visible or not. c) Performance was better for the \u201cNo load\u201d condition with opaque cups (logistic regression, p < 0.001). Error bars indicate 95% confidence intervals. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 3 Gaze displacement from the bottom of the cup at the time the cup is being loaded a) Gaze distance across the different routines. The \u201cLift\u201d routine causes the biggest displacement from the bottom of the cup (linear regression, p <0.0001), while the \u201cNo ball\u201d routine produces the smallest one (linear regression, p < 0.0001). b) Gaze displacement was similar for the \u201cClear Cups\u201d and \u201cOpaque Cups\u201d conditions. c) Gaze displacement was similar for the \u201cFace\u201d and \u201cNo face\u201d conditions. Error bars indicate the standard error from the mean across subjects. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts Figure 4 Effects of learning in perceptual reports and gaze distance a) The number of late findings (placings reported after the magician shows what is under the cups) goes down with the trial number in the conditions with the opaque cups, while is very low during the experiment for the conditions with clear cups. The correlation between the trial number and the number of late findings is statistically significant in the conditions with opaque cups (logistic regression, p < 0.01). b) Probability of subjects reporting correctly the loading of the third cup in the conditions with clear cups as a function of the trial number. The relationship is statistically significant (logistic regression, p < 0.001). c) The reaction times of the subjects reporting the loading of the third cup (in the conditions with clear cups) decreased with the number of trials (linear regression, p < 0.05). d) Similarly, the gaze distance to the bottom of the cup decreased with the trial number (linear regression, p < 0.01). Error bars indicate standard error from the mean across subjects. Pre Prin ts Pre Prin ts Pre Prin ts Pre Prin ts", |
| "url": "https://peerj.com/articles/20/reviews/", |
| "review_1": "Linsheng Song \u00b7 Jan 8, 2013 \u00b7 Academic Editor\nACCEPT\nThe manuscript is well revised and can be accepted for PeerJ. Thanks.", |
| "review_2": "Linsheng Song \u00b7 Dec 20, 2012 \u00b7 Academic Editor\nMINOR REVISIONS\nThe manuscript is well written and orgnized. The experiments were conducted in an appropriate manner and data were moderately well presented. It is potentially interesting for researches on iodine nutrition and toxicity in cod larvae. As the reviewers suggested, some tables and figures in the manuscript should be improved.", |
| "review_3": "Karin PITTMAN \u00b7 Dec 19, 2012\nBasic reporting\nThis is a well-written and timely article based on a robust experimental design and thorough analyses. Unfortunately the manuscript mentions two Tables that were not included in the files I received. The figures are all relevant although the figure legends could have been more specific about how many separate figures were meant to be embraced by the figure legend (please insert something like \"Fig. 2 A-G\" at the beginning of the legend). Otherwise the manuscript is of very high intellectual and technical standards.\n\nMinor point: line 226-228 uses the word sample 4 times.\nExperimental design\nThe experimental design was clearly stated and reproducible by those wishing to expend the energy. It was clearly suitable for the question. All standards and codes of conduct have been adhered to.\n\nThe description of the radiography and especially measurement of the neck angle is too brief to be useful (1.5 lines), although the results of this analysis are mentioned in Discussion.\n\nI also had a small question about how the number of follicles was counted (lookup sections?).\n\nOnly one other question arose in my mind, regarding the admixture of rotifers from Control and High iodine enrichments to create a Medium Iodine diet. I can see no suggestion of selectivity by the cod larvae, which would have resulted in high variations for that group, so this may not be important at all.\nValidity of the findings\nThe findings are comprehensively given and analysed. The mortality of one tank changed some of the statistical analyses but this is a minor point. The findings are justified and are put into several relevant contexts: that of dietary requirements and interactions, that of source of water used to rear the larvae (recirculation, wellwater or seawater) and that of longterm effects.\n\nIt might be interesting to have a line or two about synthesis of thyroid hormones in other organs than the thyroid follicles (it happens in fish) and what the \"gross signs\" of iodine deficiency would be in larvae (line 377).\nAdditional comments\nNice work. I like the clear statement about iodine requirements and the codicil about nutrient interactions.\n\nIt would be useful to have the two missing tables, therefore I am recommending \"Minor revisions\".\nCite this review as\nPITTMAN K (2013) Peer Review #1 of \"Iodine nutrition and toxicity in Atlantic cod (Gadus morhua) larvae (v0.1)\". PeerJ https://doi.org/10.7287/peerj.20v0.1/reviews/1", |
| "review_4": "Reviewer 2 \u00b7 Dec 13, 2012\nBasic reporting\nthe manuscript is well written and organized properly\nExperimental design\nyes\nValidity of the findings\nyes\nAdditional comments\nThe manuscript describes effect of Iodine on Atlantic cod (Gadus morhua) larvae. Overall, the manuscript is well written and organized properly, I think the manuscript is suitable for the journal of \u201cThe PeerJ\u201d at current status. Herein, the comments and suggestions are given below in an attempt to improve the paper.\n1) In the abstract section, the sentence \u201clarval Atlantic cod (Gadus morhua) were fed rotifers enriched to intermediate (26 mg I kg -1 dry weight; MI group) or copepod (129 mg I kg -1 DW; HI group) I levels and compared to cod larvae fed control rotifers (0.6mg I kg -1 DW).\u201d should be revised. I could not find any evidence you used copepod for feed trial in Material and method section.\n2) the manuscript contained so many Figures, I recommend the author should be integrated some of them together.\nCite this review as\nAnonymous Reviewer (2013) Peer Review #2 of \"Iodine nutrition and toxicity in Atlantic cod (Gadus morhua) larvae (v0.1)\". PeerJ https://doi.org/10.7287/peerj.20v0.1/reviews/2", |
| "pdf_1": "https://peerj.com/articles/20v0.2/submission", |
| "pdf_2": "https://peerj.com/articles/20v0.1/submission", |
| "all_reviews": "Review 1: Linsheng Song \u00b7 Jan 8, 2013 \u00b7 Academic Editor\nACCEPT\nThe manuscript is well revised and can be accepted for PeerJ. Thanks.\nReview 2: Linsheng Song \u00b7 Dec 20, 2012 \u00b7 Academic Editor\nMINOR REVISIONS\nThe manuscript is well written and orgnized. The experiments were conducted in an appropriate manner and data were moderately well presented. It is potentially interesting for researches on iodine nutrition and toxicity in cod larvae. As the reviewers suggested, some tables and figures in the manuscript should be improved.\nReview 3: Karin PITTMAN \u00b7 Dec 19, 2012\nBasic reporting\nThis is a well-written and timely article based on a robust experimental design and thorough analyses. Unfortunately the manuscript mentions two Tables that were not included in the files I received. The figures are all relevant although the figure legends could have been more specific about how many separate figures were meant to be embraced by the figure legend (please insert something like \"Fig. 2 A-G\" at the beginning of the legend). Otherwise the manuscript is of very high intellectual and technical standards.\n\nMinor point: line 226-228 uses the word sample 4 times.\nExperimental design\nThe experimental design was clearly stated and reproducible by those wishing to expend the energy. It was clearly suitable for the question. All standards and codes of conduct have been adhered to.\n\nThe description of the radiography and especially measurement of the neck angle is too brief to be useful (1.5 lines), although the results of this analysis are mentioned in Discussion.\n\nI also had a small question about how the number of follicles was counted (lookup sections?).\n\nOnly one other question arose in my mind, regarding the admixture of rotifers from Control and High iodine enrichments to create a Medium Iodine diet. I can see no suggestion of selectivity by the cod larvae, which would have resulted in high variations for that group, so this may not be important at all.\nValidity of the findings\nThe findings are comprehensively given and analysed. The mortality of one tank changed some of the statistical analyses but this is a minor point. The findings are justified and are put into several relevant contexts: that of dietary requirements and interactions, that of source of water used to rear the larvae (recirculation, wellwater or seawater) and that of longterm effects.\n\nIt might be interesting to have a line or two about synthesis of thyroid hormones in other organs than the thyroid follicles (it happens in fish) and what the \"gross signs\" of iodine deficiency would be in larvae (line 377).\nAdditional comments\nNice work. I like the clear statement about iodine requirements and the codicil about nutrient interactions.\n\nIt would be useful to have the two missing tables, therefore I am recommending \"Minor revisions\".\nCite this review as\nPITTMAN K (2013) Peer Review #1 of \"Iodine nutrition and toxicity in Atlantic cod (Gadus morhua) larvae (v0.1)\". PeerJ https://doi.org/10.7287/peerj.20v0.1/reviews/1\nReview 4: Reviewer 2 \u00b7 Dec 13, 2012\nBasic reporting\nthe manuscript is well written and organized properly\nExperimental design\nyes\nValidity of the findings\nyes\nAdditional comments\nThe manuscript describes effect of Iodine on Atlantic cod (Gadus morhua) larvae. Overall, the manuscript is well written and organized properly, I think the manuscript is suitable for the journal of \u201cThe PeerJ\u201d at current status. Herein, the comments and suggestions are given below in an attempt to improve the paper.\n1) In the abstract section, the sentence \u201clarval Atlantic cod (Gadus morhua) were fed rotifers enriched to intermediate (26 mg I kg -1 dry weight; MI group) or copepod (129 mg I kg -1 DW; HI group) I levels and compared to cod larvae fed control rotifers (0.6mg I kg -1 DW).\u201d should be revised. I could not find any evidence you used copepod for feed trial in Material and method section.\n2) the manuscript contained so many Figures, I recommend the author should be integrated some of them together.\nCite this review as\nAnonymous Reviewer (2013) Peer Review #2 of \"Iodine nutrition and toxicity in Atlantic cod (Gadus morhua) larvae (v0.1)\". PeerJ https://doi.org/10.7287/peerj.20v0.1/reviews/2\nReview 5: nan\nReview 6: \n", |
| "LLM_extracted_review": "['Review 1: The manuscript is well revised and can be accepted for PeerJ. Thanks.\\n\\nReview 2: The manuscript is well written and organized. The experiments were conducted in an appropriate manner and data were moderately well presented. It is potentially interesting for researches on iodine nutrition and toxicity in cod larvae. Some tables and figures in the manuscript should be improved.\\n\\nReview 3: This is a well-written and timely article based on a robust experimental design and thorough analyses. Unfortunately, the manuscript mentions two Tables that were not included in the files. The figures are all relevant, although the figure legends could have been more specific. The description of the radiography and measurement of the neck angle is too brief to be useful. There is a small question about how the number of follicles was counted. The admixture of rotifers from Control and High iodine enrichments may not be important. The findings are comprehensively given and analyzed, but the mortality of one tank changed some of the statistical analyses. It might be interesting to have a line or two about synthesis of thyroid hormones in other organs and the gross signs of iodine deficiency in larvae. It would be useful to have the two missing tables.\\n\\nReview 4: The manuscript is well written and organized properly. The manuscript describes the effect of Iodine on Atlantic cod larvae. The comments and suggestions include revising a sentence in the abstract regarding copepod feed trials, and integrating some of the figures together.']" |
| } |
