Symposium: Attention, perception, and memory in scene analysis
Wednesday, Sep 9, 2015
Hörsaal 3

Contextual influences on object recognition – evidence from SSVEPs

Ulla Martens1 & Thomas Gruber2

1Institute of Cognitive Science, University of Osnabrück, Osnabrück, Germany
2Department of Psychology, University of Osnabrück, Osnabrück, Germany

Contextual knowledge is stored in memory and the strength of associative links between an object and a given context should facilitate recognizing this object in this context. In other words, the context triggers expectations of the occurrence of certain objects. Objects which possess a low probability of appearing in a certain context are fixated earlier, more often and longer and thus, attract more attention. We investigated this influence of context on object recognition by means of an SSVEP experiment, using the method’s major advantage to separate brain responses elicited by simultaneously presented stimuli. In particular, we tagged concurrently presented backgrounds and objects with different presentation frequencies. As a result, background and object elicited different SSVEPs, which were separately quantified in the frequency domain. Analyzing the effects of semantic consistency, SSVEPs related to background processing showed higher amplitudes in the consistent as opposed to the inconsistent condition, whereas object-related SSVEPs showed the reversed pattern of effects. Thus, if all image parts were semantically related, attention was rather directed to the background. Semantic inconsistency instead led to higher attention towards the object. Right inferior and middle frontal neuronal sources of the inconsistency effect indicated a top-down attentional shift from the background to the object. This can be interpreted as the result of a mismatch between background-based expectations and semantic object representations. A clear lateralization of the consistency effect in the anterior temporal lobes indicates functional hemispheric asymmetries in processing background- and object-related semantic information.