Perceived Chasing is Object-Based
 
 
Here are some demonstrations of the various conditions discussed in the following paper:
van Buren, B., Gao, T., & Scholl, B. J. (in press). What are the underlying units of perceived animacy?: Chasing detection is intrinsically object-based. Psychonomic Bulletin & Review.
These demonstrations are provided as Quicktime movies, which can be downloaded or viewed directly in most web-browsers. These movies are a bit large and choppy, but they should be sufficient to illustrate the basic conditions. As highly compressed versions of the original stimuli, these movies may not preserve the precise spatial and temporal characteristics of the originals.  
 
One of the most foundational questions that can be asked about any visual process is the nature of the underlying 'units' over which it operates -- e.g. features, objects, or spatial regions. Here we address this question in the context of the perception of animacy. Even simple geometric shapes appear animate when they move in certain ways. Do such percepts arise whenever any visual feature moves appropriately, or do they require that the relevant features first be individuated as discrete objects?  
 
Sample Connected Trial (Descriptions) (672 KB)
Sample Unconnected Trial (Descriptions) (656 KB)
Observers viewed displays in which one disc (the 'wolf') chased another (the 'sheep') among several moving distractor discs. Critically, two pairs of discs were also connected by visible lines. In the Unconnected condition, both lines connected pairs of distractors; but in the Connected condition, one connected the wolf to a distractor, and the other connected the sheep to a different distractor. First, we simply explored how observers would experience and describe such animations, when asked to pay special attention to the initially-blinking shapes. Observers in the Connected condition were much less likely to describe such displays using mental state terms.  
 
Chasing Present - Both Connected ( (212 KB)
Chasing Present - Both Unconnected (204 KB)
Chasing Absent (Mirror Control) - Both Connected (192 KB)
Chasing Absent (Mirror Control) - Both Connected (CHEAT) (204 KB)
Chasing Absent (Mirror Control) - Both Unconnected (208 KB)
Chasing Absent (Mirror Control) - Both Unconnected (CHEAT) (220 KB)
Beyond phenomenology, we explored the influence of connectedness and objecthood on the objective ability to detect chasing. Signal detection analyses were used to explore the ability to discriminate chasing displays from inanimate control displays in which the wolf moved toward the sheep's mirror-image (a manipulation that controls for correlated motion). Chasing detection was severely impaired on Connected trials: observers could readily detect an object chasing another object, but not a line-end chasing another line-end -- even though the line ends were still readily discriminable. We conclude that the underlying units of perceived animacy are discrete visual objects. Here we include demonstrations of all four trial types, along with additional 'cheat' movies (that our observers never saw) where the invisible 'mirror-image' target of the wolf in the Chasing Absent trials is drawn as an outlined disc.  
 
Chasing Present - Sheep Connected ( (200 KB)
Chasing Present - Wolf Connected ( (232 KB)
Chasing Absent (Mirror Control) - Sheep Connected (184 KB)
Chasing Absent (Mirror Control) - Sheep Connected (CHEAT) (224 KB)
Chasing Absent (Mirror Control) - Wolf Connected (176 KB)
Chasing Absent (Mirror Control) - Wolf Connected (CHEAT) (204 KB)
We also showed, in an additional experiment, that disrupting the objecthood of either the wolf or sheep was sufficient to dramatically disrupt objective chasing detection. In these experiments, the Unconnected trials were similar to those above, but in the Connected conditions, only the wolf or the sheep (but not the other) was connected to a distactor.