It is well known that humans and other animals can recognize biological motion when shown only a point-light display. Other research has shown that social cues are deeply embedded in our perceptual system. We can also perceive emotions and intentions in simple geometric displays.
So what is going on in our brains while we watch such displays? A team of researchers led by Johannes Schultz found some answers (Johannes Shultz, Hiroshi Imamizu, Mitsuo Kawato, and Chris Frith, “Activation of the Human Superior Temporal Gyrus during Observation of Goal Attribution by Intentional Objects,” Journal of Cognitive Neuroscience, 2004). The team, based in the Wellcome Department of Imaging Neuroscience in London and the ATR Computational Neuroscience Laboratories in Kyoto, took MRI images of volunteer’s brains while they watched a simple animated display.
The display showed a red dot moving in an arc, which was then “followed” by a blue dot in one of two possible paths. Either the blue dot simply followed the same arc as the red dot, or it “predicted” where the red dot was going and took a straight-line path to intercept it. Observers were asked to either indicate whether the blue dot “caught” the red dot, or to describe the “strategy” the blue dot used to pursue the red dot. Here’s a map of one portion of the brain that is activated during the task:
The amount of activity in the active area, called the superior temporal gyrus (STG), is plotted on the small graph in the corner. The blue bars correspond to the “strategy” task, when observers were asked to describe the dot’s strategy. The red bars are for the “outcome” task, when participants needed only to indicate whether the blue dot successfully “caught” the red dot. The P and F columns indicate whether the blue dot “predicted” the path of the red dot or simply followed it along its curved path. As you can see, the STG is more active when observers try to explain the dot’s strategy, and also more active when the blue dot seems to “predict” where the red dot is going.
The STG is known to be responsible for both perception of biological motion and of intention. This result suggests that humans are quite ready to assign “intention” to any object, and that they use the same area of the brain to do this, whether the object is an inanimate dot or an academy-award-winning actor.