Evaluating the relationship between the structural description system and semantic memory with a new reality decision task

In reality decision tasks, subjects have to decide whether a picture represents a real or an unreal object: the visual features of the stimulus are compared with the visual representations of objects that have been seen previously, and stored in the so called “structural description system”; when matching occurs, the stimulus is recognized as real. One critical issue in cognitive neuropsychology is whether this system is a pre-semantic and isolated store, or whether it is connected to the semantic system or even integral to it. In the present study we set up an object decision task, where we manipulated the semantic and perceptual features of stimuli. We created a set of 200 line drawings, half real, and half not real, chimeric drawings. The two parts of chimeras were semantically related for half of the stimuli, and not semantically related for the other half. Twenty normal subjects (age range: 25-40, education: university degree) participated into the study. Reaction times and accuracy were recorded. Repeated measure ANOVA showed longer reaction times and lower accuracy for unreal with respect to real stimuli, and for semantically related with respect to unrelated chimeras. These results may be better explained in the view of an access to semantic information, when performing a reality decision task, rather than with the hypothesis of a pre-semantic locus for reality judgements