Disentangling dimensions of animacy in human brain and behaviour

Abstract

AbstractThe perception of animate things is of great behavioural importance to humans. Despite the prominence of the distinct brain and behavioural responses to animate and inanimate things, however, it remains unclear which of several commonly entangled properties underlie these observations. Here, we investigate the importance of five dimensions of animacy: “being alive”, “looking like an animal”, “having agency”, “having mobility”, and “being unpredictable” in brain (fMRI, EEG) and behaviour (property and similarity judgments) of 19 subjects using a stimulus set of 128 images that disentangles the five dimensions (optimized by a genetic algorithm). Our results reveal a differential pattern across brain and behaviour. The living/non-living distinction (“being alive”) was prominent in subjects’ judgments, but despite its prominence in neuroscience literature, did not explain variance in brain representations. The other dimensions of animacy explained variance in both brain and behaviour. The “having agency” dimension explained more variance in higher-level visual areas, consistent with higher cognitive contributions. The “being unpredictable” dimension instead captured representations in both lower and higher-level visual cortex, possibly because unpredictable things require attention. Animacy is multidimensional and our results show that distinct dimensions are differentially represented in human brain and behaviour.