#TheDress Seen in a New Light

At this point, I’m sure most of you have seen the dress image that has taken the internet by storm. If you teach psychology, you’ve probably also received an onslaught of emails from fascinated students. What we have here is a teachable moment!

Here is the original image (or, at least, the image that was first introduced to me by cognitive scientist extraordinaire, Whitney Hansen):


borrowed from http://gawker.com/

What do you see? Is that dress gold and white or black and blue? I saw gold and white. My wife disagreed. I think our marriage is over. The meme made the internet rounds so quickly that there is rampant speculation about the basis of the effect. However, a story over at Wired.com has it exactly right. The dress is legitimately black and blue. Those who see it as gold and white are inappropriately “adjusting” their perceptions of color to account for perceived changes in illumination.

Our perceptions of color aren’t based solely upon activity in our photoreceptors. They can easily be influenced by context. We know that a blue object is blue regardless of whether we’re seeing it in direct sunlight or in a dimly-lit room. The signal (the amount of reflected light) changes, but our interpretation does not. Our brains adjust to these differences in illumination so that our perceptions stay relatively constant. In this image, the lighting conditions are ambiguous. Is the dress brightly lit or in shadow? It’s unclear. It turns out, if you interpret the dress to be in shadow, you see gold and white. If you interpret it to be brightly lit, you see black and blue.

To make this unconscious adjustment more transparent, I’ve adapted a rather famous illusion (developed by Purves and Lotto, 2002) using colors sampled directly from the dress image above. The black cube at the top of the image is exactly the same color as the cube that is perceived to be gold at the bottom. Same goes for the blue cube on top and the one perceived to be white on the bottom. Your perceptions change due to assumptions about lighting, and these assumptions are non-conscious. I defy you to “turn off” the illusion below!

Thanks to Beau Lotto for permission to adapt his beautiful illusion.

Thanks to Beau Lotto for permission to adapt his beautiful illusion.

TEDx Science of Magic

The science of magic is becoming something of a cottage industry, providing many magicians a new framework in which to present their material.  Mini-conferences like Ignite, BarCamp, and TEDx, that cater to broad, academically savvy audiences, are a natural place for magicians to present their ideas on the interface of the arts and sciences.  Yesterday, on a whim, I searched for YouTube videos with the keywords “TEDx” and “magic.” I was overwhelmed by the number of hits this search generated.  Magicians all over the world have participated in local TEDx events, and many of them have opined on the science underlying their methods.  Just for fun, I’ve semi-randomly sampled a selection of these videos below.  Enjoy!  If you know of any good ones that didn’t make it into this entry, please post links in the comments!


Stuart Palm:  “Human Hacking – Neuroscience & Magic” at TEDx Hong Kong University of Science & Technology


Marco Tempest (who we blogged about previously here):  “A Cyber-Magic Card Trick Like No Other” at TED Global


Suhani Shah:  “Mind, Psychology and Magic!” at TEDx Youth@Chennai


Krystyn Lambert:  “Magic, Rhyme and Reason” at TEDx Teen


Gestalt Magic Part IV: Proximity in Space & Time

(This post is the fourth in a series of entries discussing how theories developed by the Gestalt school of psychology relate to magical deception.  You may want to catch up by reading Part 1, Part 2, and Part 3.)

In Part 3 of the Gestalt Magic series, I introduced the notion of “pre-attentive” processes.  According to Ulric Neisser, one of the fathers of modern cognitive psychology, pre-attentive mechanisms act to group and parse sensations in an effort to effectively guide the deployment of attention toward salient features and objects in the perceptual field.  There is evidence that many of the Gestalt principles I’ve outlined in this series of posts happen pre-attentively, as they allow for a quick resolution of sensory ambiguity.  Under normal circumstances, these tendencies wouldn’t be apt to lead to erroneous perception.  Unfortunately, in the context of a magic show, normally adaptive operating assumptions can work against you.  For the Gestalt psychologists, illusions occurred when the order of the Gestalt grouping principles was imposed upon disorderly stimuli in an inappropriate fashion.

Perhaps the most basic of the grouping principles, but among the most important for magicians, is the law of proximity.  This rule states that objects or stimuli that are near to each other are likely to group together.  For example, in the figure below, you’re likely to group the stimuli as a series of columns by virtue of the closer proximity of vertical elements relative to horizontal elements, and this tendency even overcomes any disruption caused by the addition of dissimilar elements in the array.

While the Gestaltists tended to focus on visual groupings, many of their principles also apply to other modalities.  For example, many of the same grouping principles apply to the parsing of an auditory stream.  The brain does a good job of filling in auditory stimuli that are masked by environmental noise, analogously to the filling-in that occurs with visual good continuation (see the phonemic restoration effect).  Even more generally, the law of proximity is likely to apply temporally.  Ventriloquism depends upon your tendency to group stimuli based on temporal proximity.  When a ventriloquist moves a dummy’s mouth to match the rhythm of the speech sounds he or she is producing, you can’t help but to mis-localize the source of the sound as coming from the dummy’s mouth!   Magicians exploit temporal proximity in a phenomenon known as time misdirection (Lamont & Wiseman, 1999).  Actions happening in close temporal proximity are often perceived as causally related.  Thus, magicians attempt to distance the true method used to accomplish an effect (i.e., “the tricky business”) from the moment that the effect is revealed so that their relationship goes unperceived.  Often times, the piece of sleight of hand responsible for an illusion happens before the audience even realizes that the magic trick has started.

In the first installment of the Gestalt Magic series, I described a very simple magic trick:

The magician presents a coin held in his left hand.  He transfers the coin to his right hand so that he can reach into his left pocket to retrieve a pen (a makeshift magic wand).  Upon tapping his right hand with the pen, the hand is opened to reveal that the coin has vanished.

The method used to accomplish this trick involved a false transfer of the coin from one hand to the other.  The coin was actually retained in the hand that retreated into the pocket to retrieve the “magic wand,” where the coin was ditched.  After the coin has been ditched in the pocket during the retrieval of the pen, it is in the magician’s best interest to delay the revelation that the coin has disappeared, so as to subvert realization that the two acts are causally related.  Not only is the true cause of the disappearance discounted with the addition of temporal distance, but the false cause (the tapping of the hand with the “magic wand”) is bound to the effect due to its close temporal proximity with the revelation.

Here comes the pep-talk portion of this blog entry.  Please don’t feel badly when you’re fooled by one of these simple magic effects.  The perceptual errors that magic tricks take advantage of, which I will call errors of imposition, happen to us constantly, and usually don’t reach our awareness.  Our knowledge of the world and of the probable groupings of stimuli in our environment imposes upon our perception (even when it is unwarranted).  This imposition is especially salient in the case of faces.  We are so adept at face recognition that we impose our knowledge of facial groupings on non-face stimuli almost every day.  Thus, our initial interpretation of the degraded image below is that of two people and a floating, disembodied face (perhaps Jesus?).  Further examination reveals that the face is actually a small child sitting on his father’s lap.  The immediacy of this percept suggests that the grouping of stimuli into the perception of a face is likely to be pre-attentive as is the case with other Gestalt grouping principles (Palermo & Rhodes, 2007).

source unknown

Enigmatically, we are fooled in a magic show because we are expert perceivers!  Gestalt processes facilitate fast, efficient interpretation of stimuli in our environment and are incredibly adaptive.  Although the Gestaltists wanted to argue that these perceptual tendencies were innate, the rabid empiricist in me thinks it much more likely that they are learned through repeated experience with regularities in the environment.  In support of this assertion, developmental researchers have shown that children acquire perceptual grouping tendencies at different stages in their development, as a consequence of experience (Quinn, Bhatt, Brush, Grimes, & Sharpnack, 2002).  Unfortunately, Wertheimer never developed a compelling theory to explain the phi phenomenon, and the Gestaltists never developed a complete theory of perception to counter that of the empiricists.  Despite these failings, their laws of perceptual organization are still well-accepted by psychology and play a role in many modern perceptual theories.  Thus endeth the Gestalt Magic lesson!  Thanks for playing.


Lamont, P., & Wiseman, R. (1999). Magic in Theory. Seattle, WA: Hermetic Press. (Google Books link)

Palermo, R., & Rhodes, G. (2007). Are you always on my mind? A review of how face perception and attention interact. Neuropsychologia , 45, 75-92. (link)

Quinn, P. C., Bhatt, R. S., Brush, D., Grimes, A., & Sharpnack, H. (2002). Development of form similarity as a Gestalt grouping principle in infancy. Psychological Science , 13, 320-328. (link to abstract)

“Harvard Meets Hogwarts”

Stephanie West Allen brought to my attention a blog entry written by magician, motivational speaker, and physician, Steve Bedwell, entitled “When Harvard Meets Hogwarts:  What Can Scientists Learn From Magicians?”.  Let me start by saying that I have great respect for Bedwell as a magician and creative thinker.  The first time I saw his “Reboxed” effect performed live, it broke my brain.  His essay, which is critical of research examining the psychological and neuroscientific bases of magic, follows on the heels of Teller’s recent critique in Smithsonian Magazine (and on NPR), on which we commented here.  Unfortunately, as was the case with Teller’s article, Bedwell’s critique is rather short-sighted and based on limited information.  He argues that:

To date, much of the work that has been published on the neuroscience of magic has involved honing in on one marginal feature of extremely complex sleight-of-hand. The neuroscientific explanation of why the trick is deceptive then becomes all about this one, often tangential, subtlety.

This faulty assertion is derived, I believe, from two different problems:  One of these is a general misunderstanding of the scientific method, and one is a failure of researchers to communicate the limitations of their research.  As I noted in my commentary on Teller’s article, there is redundancy built into every piece of magic in order to optimize the odds of successful deception.  However, it is not always clear that each of these redundancies has a real effect on the audience’s perception.  This is one of the roles that science can play in the life of the magician…To determine whether the benefit of each subtlety is “real.”

More importantly, however, this “honing in” on a single element of deception is also the best route forward, as far as the scientific method is concerned.  Much research is inherently reductionistic.  That is, we have to be able to manipulate variables independently of each other in order to assess the relative contribution that each variable makes to changes in the dependent variable (in this case, deception).  Theoretically, it would be possible to design an experiment that independently manipulates every aspect of a magic trick, such as the coin vanish described in Bedwell’s essay, within a factorial design.  However, this would be extremely difficult, and the complexity of the final experiment could introduce a host of other potential confounds.  So, instead, researchers will focus on a single variable or a small number of variables that can be manipulated independently of each other without much trouble.

This was the tactic taken in a recent paper examining perception of the “French Drop,” a piece of sleight of hand often used to make a coin vanish (Otero-Millan et al., 2011).  The authors focused primarily on a single variable: the type of movement that the magician’s hand made as it retreated after feigning transfer of the coin from one hand to the other.  However, there’s a clear reason why they chose to examine only one variable.  They had a specific hypothesis that they were testing, which related only to that variable!  This is the way science works, and it should not be interpreted as being ignorant of the fact that magical deceptions are multiply-determined.  All dependent variables are influenced by myriad factors, but a good experiment holds these extra variables constant while manipulating only the variables that are relevant to the hypothesis.  It’s also important to note that science builds upon itself, so future studies may examine other variables involved in successful deception via the french drop.  The story certainly does not end with a single study.

This brings me to the second source of Bedwell’s gripe.  Scientists are apt to exaggerate the implications of their findings.  Unfortunately, this is a natural consequence of the publish-or-perish scientific culture and the nature of grant funding.  Scientists have to convince funding agencies and the rest of the scientific community that their work is important.  This is especially true for relatively new areas of inquiry, such as the science of magic.  However, if an author’s exaggerations are not tempered in print by a parallel acknowledgement that additional factors are likely to be at play in the real world, a reader who is not accustomed to “discussion section exaggerations” could come away with the impression that the authors are myopic in their handling of the problem under investigation.

Returning to Bedwell’s essay, he continued by taking aim at the inattentional blindness work of Gustav Kuhn and and Ben Tatler (2005; advisers to two of the authors of this blog), who used a magic trick to examine the relationship between inattentional blindness (our tendency to miss salient pieces of our environment while engaged in an attentionally-demanding task) and eye movements.  In the trick, the magician makes a cigarette vanish by dropping it into his lap while attention is directed elsewhere.  (Click here to see the video and learn more about the method.)  Bedwell says of Kuhn’s work:

However, any study employing magic (…) is confounded by one crucial factor. The experimental subjects are knowingly watching a magic trick and being asked to self-report on whether or not it fooled them. Here’s the problem: What about subjects who don’t see the dump of the cigarette, but figure out where the cigarette must be hiding? (…) How do the researchers distinguish between fooling both the eye and the mind, and fooling the eye but not the mind? This is especially relevant with experiments that employ unsophisticated magic tricks because, while this makes for relatively simple analysis, the tricks are also easily figured out.

As was the case with much of Teller’s critique of the science of magic, Bedwell demonstrates that he has a very limited knowledge of the work that has actually been carried out in this field.  The “crucial factor” that he sees as a confound for the whole research program has, in fact, been accounted for within the design.  In Kuhn and Tatler’s original study, only half of the participants knew that they were about to watch a magic trick.  Beyond this, they were given extra information that usually isn’t available to audience members at a magic show.  They were told exactly what was going to happen in the magic trick, and that their job was to figure out how the magic trick was accomplished.  The other half believed that they were about to take part in a picture-rating task.

Surprisingly (and problematically for Bedwell’s critique), it turned out that the two groups differed very little in their viewing of the magic trick.  Gaze patterns during viewing of the magic trick did not differ between groups, and rates of inattentional blindness differed very little, as well.  None of the uninformed participants detected the method behind the magic trick, and only two of ten informed participants detected the falling cigarette, despite the fact that they had scads of information that should have helped them deploy their attention appropriately to detect the drop.  Thus, Bedwell’s confound is hardly that.

Bedwell also fails to appreciate that the 2005 paper which he referenced was only the first in a line of experiments using this magic trick to examine inattentional blindness.  Remember how science builds upon itself?  Each additional paper refined the method and addressed further potential confounds and considerations.  Specifically, both Kuhn et al. (2008) and Kuhn and Findlay (2010) assessed whether participant inference undermined their findings, as Bedwell suggested in his critique.  It turns out that Bedwell’s criticism is another relative non-issue.  If you watched the video in the link above, you may have noted that the cigarette vanish followed the disappearance of a cigarette lighter (using the same methodology).  In addition to asking participants whether they detected how the cigarette vanish was accomplished, Kuhn et al. (2008) asked participants how the lighter disappeared.  None of the participants who detected the falling cigarette claimed knowledge of how the lighter was made to vanish.  Had they inferred information about the cigarette (detected with their minds rather than their eyes, in Bedwell’s terms), it would not have been a far leap to generalize that inference to the lighter vanish.  Since none made this generalization, it suggests that there was minimal inference driving participant behavior.  For this subset of participants, the cigarette drop did not fool their eyes or their minds, but the lighter vanish, using an identical methodology, fooled both!

Furthermore, Kuhn and Findlay (2010) directly assessed the inference hypothesis through a manipulation in their methodology.  They instituted a “fake” condition where the falling object was digitally edited out of the video.  Thus, if participants reported detection of a falling object, it could only be the result of inference, as there was no object to detect!  Their eyes should be fooled, but their minds shouldn’t be.  In this condition, none of the participants reported seeing how the trick was accomplished (which is good!).  However, when prompted to guess at the method, 40% of participants correctly inferred that the object was dropped.  In the “real” condition (where the object was visibly dropped), no participants who failed to detect the drop inferred the correct method.  These results suggest that participants can successfully dissociate perception from inference and are generally honest in their self-reports, undermining Bedwell’s critique.

We at the “Science of Magic” blog do glean one very important point from Bedwell’s piece.  While, as I’ve tried to demonstrate, his inference hypothesis is not a problem for Kuhn’s inattentional blindness research, it is an interesting topic for future research.  What are the limits upon participants’ abilities to reconstruct the method of a magic trick post hoc?  What are the variables that may interact with this inferential process?  One of these is likely to be what magicians refer to as “time misdirection,” an idea that I am planning to address in the long-awaited final entry in my “Gestalt Magic” series here on the blog.  Stay tuned on that one!

To conclude what I had intended to be a short-and-sweet blog entry, I must admit that I am rather befuddled by the group of magicians who are resistant to psychology’s interest in their methods.  Bedwell may not be among this group.  His piece opens with a generally positive perspective on the integration of science and magic.  Admittedly, it is a very small but vocal subset of the magic community that opposes this research, and most every magician with whom I have spoken personally tends to be hugely supportive of the “science of magic” movement.  Discomfort with the field of study may be due to the exaggeration inherent in popular media reporting of scientific results, which could also foster the perception that researchers have tunnel-vision when it comes to the underlying mechanisms of magic.  I am all for fighting against bad science, but uninformed critiques do a disservice to valid science by painting a warped image of the methods that are used in the laboratory on a day-to-day basis.  In a society whose political climate tends to undervalue science, dissemination of this kind of misinformation only acts to strengthen an irrational bias against the scientific establishment on the whole.


Kuhn, G. & Findlay, J. M. (2010). Misdirection, attention and awareness: Inattentional blindness reveals temporal relationship between eye movements and visual awareness. Quarterly Journal of Experimental Psychology, 63, 136-146. (link)

Kuhn, G. & Tatler, B. W. (2005). Magic and fixation: Now you don’t see it, now you do. Perception, 34, 1155-1161. (link)

Kuhn, G., Tatler, B. W., Findlay, J. M., & Cole, G. G. (2008). Misdirection in magic: Implications for the relationship between eye gaze and attention. Visual Cognition, 16, 391-405. (link)

Otero-Millan, J., Macknik, S. L., Robbins, A., & Martinez-Conde, S. (2011). Stronger misdirection in curved than in straight motion. Frontiers in Human Neuroscience, 5: 133. (link)

The Token Skeptic Podcast: On Magic & Psychology

A couple of weeks ago, I had the pleasure of being interviewed by Kylie Sturgess, producer of the Token Skeptic podcast.  We chatted about future directions in the science of magic and its place in history as well as some of my ongoing research and upcoming course on the psychology of magic.  I closed the interview with a card trick that you can try at home, so have your deck of cards handy!  You can listen to the interview over on the Token Skeptic website here:  http://tokenskeptic.org/2012/07/13/episode-one-hundred-and-twenty-six-on-magic-and-psychology-interview-with-anthony-barnhart/

Stay-At-Home FISM 2012: RESULTS!

FISM 2012 is over, and the results are in!  I hate to brag (not really), but I was pretty darned prescient in my FISM predictions, this year.  Yu Ho Jin, who I featured on July 10, won first place in the manipulation category and the Grand Prix in stage magic!  Yann Frisch, the quirky magician I featured on July 11, took home first place in the parlour magic category and the Grand Prix in close-up magic.  However, I dropped the ball in the stage illusion category.  I predicted that Cubic Act would take home the Invention Award.  While they did place 2nd in the stage illusion category, the Invention Award was given to Mr. Tango, a coin magician who performed a routine telling the story of Jesus.  I am unable to find a video of this performance, but I’d be quite curious to see it!  Zeki Yoo ended up taking home the third place prize in card magic, and Kim Hyun Joon took third place in stage manipulation.

To wrap up this year’s Stay-At-Home FISM, I want to share video of a couple of the winning acts that weren’t featured in previous blog entries.  First, the winner of the stage illusion category, Marcel Prince of Illusions.  Word on the street is that he won the category handily with his dark, theatrical act:

Finally, from Finland, Marko Karvo took home the first prize in the general stage magic category with his elegant dove magic…a category that has generally be under-represented in my Stay-At-Home FISM entries.

The rest of the award winners can be found over on the Magic Convention Guide.  I’ll see you for another Stay-At-Home FISM in 2015, unless I can pull together the funds for a trip to Rimini, Italy! Ciao!

Stay-At-Home FISM 2012: Franz Koffer

Franz Koffer represents Hungary in the General Stage Magic category.  He may be competing with an act other than the one in the video below, because this would be rather clearly categorized as a manipulative act.  However, I thought it was worthy to be included in a blog entry.  Koffer establishes an interesting character the moment he walks out on the stage.  His quirky style of dress and steamer trunk immediately make me think of the Ali Hakim character from the musical “Oklahoma!”  Ali Hakim was a charismatic snake oil peddler who claimed to be of Persian descent.  However, his strange accent suggested that he was likely to be something other than his persona would have you believe.

I have a hunch that I’d buy almost anything Koffer tried to peddle to me after watching his act.


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