EFFECTS OF STIMULUS ARRANGEMENT ON HEMISPHERIC-DIFFERENCES AND INTERHEMISPHERIC INTERACTION FOR PROCESSING LETTER TRIGRAMS

Observers identified consonant-vowel-consonant (CVC) nonsense syllable s with the letters arranged horizontally. In each of 2 experiments, th ere were fewer errors when stimuli were presented to the right visual field (RVF) and left hemisphere (LH) than when stimuli were presented to the left visual field (LVF) and right hemisphere (RH), and the exte nt to which the number of last-letter errors exceeded the number of fi rst-letter errors was greater on LVF/RH than on RVF/LH trials. When th e same stimulus was presented simultaneously to both visual fields (Ex periment 2), the qualitative error pattern was very similar to the pat tern obtained on LVF/RH trials. These effects replicate results obtain ed in earlier CVC identification experiments with letters arranged ver tically. However, when a single stimulus was presented in the center o f the visual field (Experiment 1), so that the first letter of the CVC projected to the LVF/RH and the last letter projected to the RVF/LH, the error pattern was a mixture of the LVF/RH and RVF/LH patterns, as if each hemisphere took the lead for processing the letter it received directly.