Hemi-field asymmetries in memory for incongruous scenes

The purpose of the present study was to investigate hemispheric asymmetries of long-term semantic memory in normal subjects. A hemi-field reaction time (RT) and accuracy paradigm was used and the test stimuli consisted of pictures, with different semantic organization. Two separate experiments were conducted. In the first, memory for pictures depicting common scenes or incongruous scenes was measured. In the second, we compared memory for incoherent scenes and the same incongruous scenes. The results showed no difference between the visual half-fields in accuracy scores. However, in both experiments the RT results showed that incongruous scenes were recognized consistently faster in the right visual half-field than in the left half-field. In addition, in the first experiment there was no visual field difference for common scenes. In the second experiment, there was a left visual field advantage for unorganized scenes. The results were interpreted to reflect hemispheric asymmetry in long-term semantic memory, in general, and showing a left hemisphere specialization for uncommon, unusual aspects of otherwise regular percepts, in particular. Applying schemata theory to the results, we discussed the possibility that the left hemisphere uses/stores schemata conducive to "flexible" thinking strategies while the right hemisphere uses/stores schemata that involve "rigid" thinking strategies.