Imagine watching a group of students standing in a circle throwing a basketball back and forth. Right in the middle of the game, a gorilla walks across the scene, right through the middle of all the action. Would you notice? One would think that the appearance of a gorilla would be an obvious disruption in the game; however, in a real study illustrating this very same example, approximately half of the participants failed to notice the unexpected appearance of the gorilla in the scene (Simons & Chabris 1999). This phenomenon of "change blindness," or the inability to notice a change in scene after a brief visual disturbance, has always intrigued me ever since I first learned about it in my PGS 101 class and then again in my PSY 324 Memory and Cognition class. Recently, while studying illusions in this class, I once again came across yet another example of change blindness in relation to sensation and perception with this video. For full effect, make sure to watch the video first before reading the explanation below!
After watching the video for myself, I couldn't believe that I could simply overlook so many obvious changes occurring right before my eyes. I even had to re-watch the video to make sure that the color changes were true, and much to my dismay, I found that my eyes really did deceive me. But how does this happen? Similar to the video of gorilla in the background, dramatic changes take place in the midst of all the action, causing these changes to unintentionally go unnoticed. Even though the video title warns the viewer that there will be a color change involving one of the cards at some point during the magic trick, it is hard to detect the several changes occurring simultaneously during the video. The viewer is so focused on watching the card trick that it is easy to miss the other substantial changes such as the changes in shirt color, the change in table color, and the change in background color. This failure to detect such change may be caused by the fact that the stimuli are noticed but not consciously perceived. Because we have "selective" conscious attention, we are only able to concentrate our awareness on a limited portion of our sensory input (Fisher 2009). It is also possible that saccadic eye movements can hinder the ability to perceive changes between scenes since they are so quick and numerous.
For more information about change blindness, also check out J. K. O'Regan's website: http://nivea.psycho.univ-paris5.fr/ and especially be sure to watch this demo used in one of his experiments demonstrating how "mudsplashes" cause change blindness: http://nivea.psycho.univ-paris5.fr/CBMovies/ObeliskMudsplashMovie.gif. Enjoy!
By: Katie Travis
References:
Fisher, M. (2009, May 17). Sensation and perception. Psychology in the News. Retrieved November 7, 2011, from http://intro2psych.wordpress.com/category/sensation-perception/
O’Regan, J. K., Rensink, R. A., & Clark, J. J. (1999) Blindness to scene changes caused by “mudsplashes”. Nature, 398(34).
Simons, D. J. & Chabris, C. F. (1999). Gorillas in our midst: sustained inattentional blindness for dynamic events. Perception, 28: 1059-1074.
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