Hemispheric differences in visual detection as a function of skill

Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)




William J. Hoyer


Developmental psychology, Psychology, Experiments

Subject Categories

Cognition and Perception


The present study examined perceptual asymmetries in a sample of medical technologists and a control group as a function of domain-specific knowledge. Skill and visual field differences were investigated in a bacteria recognition task. Skilled individuals were significantly faster and more accurate than controls under each probe conditions (i.e., positive, "easy" negative, "difficult" negative). These results indicate that knowledge representations facilitated recognition ability in the skilled group.

Medical technologists exhibited a significantly lower error rate than controls under RVF(LH) presentations during positive probes. No skill differences were observed during LVF(RH) presentations. This finding is consistent with Goldberg and Costa's (1981) model of hemispheric specialization, suggesting that "descriptive systems" (i.e., cognitive strategies) are utilized by the left hemisphere during skilled performance. Expected skill by visual field differences for "difficult" negative probes were not observed.

The present study also examined perceptual asymmetries under interstimulus intervals (ISI) of 50 ms and 1000 ms. Controls were slower under the 1000 ms ISI condition relative to medical technologists. Expected visual field differences under the 1000 ms ISI condition were not observed. This result suggests that hemispheric asymmetries related to skill may emerge during early sensory analysis, as well as later stages of information processing. Several block by visual field interactions were also observed that are consistent with a RVF(LH) shift in asymmetry over trials during letter recognition (e.g., see Hellige, 1976) and face recognition tasks (e.g., see Ross & Turkewitz, 1982).

Visual recognition performance was relatively unaffected by age in the skilled group. The present findings support a model of adult cognition that acknowledges the important influence of domain-specific knowledge on perceptual and cognitive skills with age (e.g., see Clancy & Hoyer, 1989; Rybash, Hoyer, & Roodin, 1986).

The results of the present study suggest that some components of skilled performance may be related to hemispheric specialization. A goal of future research is to examine how the two hemispheres act in unison during skilled visual performance. It is suggested that systematic research based on computational model of hemispheric processing is needed to examine hemispheric differences in skilled processing under varied stimulus input (e.g., degradation) and task conditions (e.g., classification, detection, visual search).