Intrahemispheric visual-motor information processing and cerebral functional lateralization.

A series of stimuli, words and faces, were presented tachistoscopically to 24 dextrals and 12 sinistrals. The stimuli were presented to one eye at a time and the subjects were instructed to respond to specific words or stimuli with a specific hand. The results indicate that (1) cerebral functional asymmetry is related to handedness; in the dextrals, the left hemisphere is more specialized in verbal recognition, while in the sinistrals, the right hemisphere is more specialized in recognizing non-verbal material. (2) An ipsilateral hand-and-eye combination is a valid method of measuring intrahemispheric information processing, provided that the tachistoscopically presented visual stimuli are capable of inciting specialized hemispheric function. The dominant relationship among the crossed and non-crossed visual pathways is discussed.     

Fact and fantasy: the roles of accuracy and variability in confusing imaginations with perceptual experiences

In Experiment 1, pictures were presented to subjects two, five, or eight times, and subjects were asked to imagine each pciture two, five, or eight times. Subsequently, subjects estimated the number of times each picture had been presented. Their estimates of the frequency of these external events were influenced by imagination trials; this effect was greater for good imagers than for poor imagers. Experiment 2 involved a similar design in which subjects were asked either to imagine the same referent for a word or to imagine a different referent for a word on successive imagination trials. Consistency (same referent) did not increase the influence of imaginations on immediate judgments of external frequency. Thus, the results of Experiment 1 were attributed to the greater accuracy (as opposed to greater consistency) of good imagers' internal generations of the stimuli. Furthermore, variation (imagining different referents), like greater accuracy, increased the effects of imagination trials on immediate but not on delayed judgments of frequency. Possible mechanisms underlying these effects are discussed. In general, the two studies show that qualitative characteristics of completely covert generations influence their impact on estimates of the frequency of external events.