February 28, 2009

Video representation of the 'Thatcher effect'

This is one of my favorite optical illusions and it's neat to see it demonstrated on video. I like it because it reveals how facial recognition is a discreet neurological process (or processes as The Neurophilosopher has reminded me).

This illusion may be caused by specific psychological processes involved in face perception which are tuned to upright faces. Faces seem unique despite the fact that they are very similar. Humans may have developed specific processes to differentiate between faces that rely as much on the configuration (the structural relationship between individual features on the face) as the details of individual face features, like the eyes, nose and mouth. When a face is upside down, the configural processing cannot take place, so minor differences are more difficult to detect.

Interestingly, this effect is not present in people who have some forms of prosopagnosia, a disorder where face processing is impaired, usually acquired after brain injury or illness. This suggests that their specific brain injury may damage the process that analyses facial structures.


  1. That was, in fact, cool.

  2. I just happened across this:


  3. Anonymous4:12 AM

    Very interesting.

    Especially since I have a textbook at this very moment opened to the page that explains this.

    Ponder this for a moment. The area that is activated when you see a face is called the fusiform face area (FFA), a region of the extrastriate cortex located on the base of the brain. Numerous studies have concluded that this part of the brain is activated when a face or even visual cues associated with faces are seen.

    Two studies (Gauthier et all., 2000; Xu, 2005) have found that when bird or car experts, but not nonexperts, viewed pictures of birds or cars, the FFA was activated.

    I wonder.


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