Joubert O, Fize D, Rousselet G A, Fabre-Thorpe M, 2006, "What about background and context influences on ultra-rapid object categorisation?" Perception 35 ECVP Abstract Supplement
What about background and context influences on ultra-rapid object categorisation?
O Joubert, D Fize, G A Rousselet, M Fabre-Thorpe
In object identification the influence of the background remains controversial. We have shown that objects such as 'animals' and scene contexts (man-made vs natural) are categorised at similar speeds suggesting possible interactions between scene and object representations. Here, we directly test for contextual influences on object categorisation using a rapid go/no-go visual categorisation task in which subjects have to quickly lift their finger when they see an animal target (among man-made objects). In a first experiment, animals or objects were randomly presented either in their natural context or on a uniform grey background in which object segmentation should be much easier. Stimuli were flashed for only 26 ms. Subjects' performance was very high (96% accuracy, 374 ms median RT), but, remarkably, no difference was found between the two conditions. In a second experiment, animals and objects were presented randomly with either man-made or natural contexts. A mild but significant impairment of performance was observed when animals were presented in a man-made (incongruent) context (vs natural congruent context) with a 15 ms mean RT increase and a 2% accuracy decrease. The influence of context is discussed in relation with the 'accumulation of evidence' theory (Perret et al, 1998 Cognition 67 111 - 145).
[Supported by a grant from the French Government, CNRS, Université Paul Sabatier Toulouse 3.]
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