Dissociating the detection of intentionality from animacy in the right posterior superior temporal sulcus.
Gao, T., Scholl, B. J., & McCarthy, G. (2012). Journal of Neuroscience, 32: 14276-14280
In this project we demonstrate that pSTS represents an agent's shifting intentions beyond animacy. Observers viewed chasing animations, wherein one shape (the wolf) pursued another shape (the sheep). To vary intentionality independently from animacy, we employed a new wavering wolf display. This is a display that not only yields a robust percept of animacy and chasing, but also of perceived intentions that frequently change. Conceptually, this display is modeled on the idea of a wolf that is chasing some sheep, but that frequently changes its mind about which particular sheep to pursue. As a result, animacy is held constant (since the wolf is always seen to be chasing), while the perceived intentions change.
Animation 1: Changing Intentions (wavering wolf)
There are three discs, one of which was the 'wolf' (in gree), and two of which were potential 'sheep' (in red and blue). The potential sheep always moved randomly, while the wolf pursued one of the two potential sheep at any given time, frequently shifting between them. Naive observers who were simply asked to describe this animation nearly always employed terms such as "chasing", and noted the shifting intentions over time.
The display was identical to the Changing Intentions display with the important exception that the wolf chased a single sheep for the entire 10s display. The third (unchased) sheep moved along a random trajectory of the same type as the chased sheep, but its motion was not correlated (i.e., it did not interact) with either the wolf or the chased sheep.
Animation 3.1: Phantom Chasing
The Phantom Chasing display was identical to the Changing Intentions display, except that the wolf (in red) chased the mirror image of the sheep (i.e. the reflection of the sheep’s position across the center of the display) rather than the sheep itself. However, since this target of the wolf’s pursuit was invisible, the wolf’s motion was no longer perceived as goal-directed, even though it was moving in the same intrinsic manner.
Animation 3.2: Phantom Chasing (Cheating)
The display was identical to the Phantom Chasing display except that the two mirror images of the sheep were draw in dark green and blue. The wolf (in red) chased the mirror images of the two sheep in alternation. This demo illustrates how the Phantom Chasing display is generated. Observers in the experiment never saw this demo.
The Flashing display was identical to the Phantom Chasing display, except that at any moment each disc had a 10% chance of disappearing for 83.3ms and then reappearing. Subsequent disappearances of the same disc were separated by at least 833 ms. Thus, each disc appeared to flash on and off unpredictably several times during the 10s display.