The 'Units' of Perceived Animacy

Below are demonstrations of the various conditions and phenomena reported in the following paper:

van Buren, B., Gao, T., and Scholl, B. J. (2016). What are the underlying units of perceived animacy?: Chasing detection is intrinsically object-based. Psychonomic Bulletin and Review. PDF

One of the most important questions that can be asked about any visual process is what 'inputs' it operates on. It has been argued, for example, that visual working memory operates on objects (with the consequence that a very large number of features may be stored provided they belong to only a few objects). We wondered whether perceived animacy is similarly object-based -- might there be a perceptual bias to see only discrete visual objects as alive? Subjects detected chasing under two display conditions: In the Unconnected condition a 'wolf' disc chased a 'sheep' disc amid several randomly moving distractors. In the Connected condition the wolf and sheep moved identically, but each was connected to a different distractor via a thin line. In principle, the chasing motion should have been equally noticeable in both conditions, but subjects were extremely bad at detecting chasing performed by object-parts. The object-based nature of perceived animacy illustrates how the visual system encodes certain "ontological assumptions" about what can and cannot be alive.

This research was conducted in collaboration with Tao Gao.


Experiment 1 — Descriptions

In our initial experiment, we were interested simply in whether subjects would describe chasing events differently when the participants in these events were not discrete objects, but rather object-parts. Subjects were much less likely to mention mental states when describing chasing performed by line ends, compared to discs.

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Experiment 2 — Detection

How automatic is this role of objecthood? It's possible subjects in the Connected condition of Expt 1 noticed the chasing line-ends, but chose to describe them in inanimate terms. A more interesting possibility is that they failed to see chasing altogether. To test this, we asked a new sample of subjects to detect chasing performed by objects and object-parts. Since this was a detection task, we also needed displays in which chasing was not visible. We accomplished this by having the wolf chase the invisible mirror image of the sheep (this preserves low-level motion features while abolishing the chasing percept). We generated mirror-chasing analogs for the Unconnected and Connected chasing displays, and measured subjects' ability to discriminate chasing from mirror-chasing in the Unconnected and Connected conditions. Even when they were explicitly searching for chasing, subjects were much more sensitive to chasing performed by discrete objects.

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Experiment 3 — Wolf vs Sheep

How powerful is this effect? Is disrupting the objecthood of either the wolf or the sheep sufficient to impair chasing detection? We ran two new versions of our detection experiment. For half of subjects, we attached the wolf to a distractor in the Connected condition, and for the other half of subjects we attached the sheep to a distractor in the Connected condition. We found that disrupting the objecthood of either the wolf or the sheep was sufficient to impair chasing detection.

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