Performance and physiological responses of type A and type B individuals during a cognitive and perceptual-motor task.

A total of 36 male individuals, 18 classified as Type A and 18 as Type B performed a cognitive (tonal memory) and a perceptual-motor (simulated race car driving) task along with a secondary reaction time (RT) task. Heart rate (HR), skin temperature, and skin conductance (SC) were measured. Multiple linear regression analysis revealed that tracking was related to Jenkins Activity Survey indicating superior performance for those scoring high in overall Type A behavior and low in the H sub-scale (hard driving, competitive behavior). Persons scoring high in the S scale (speed and impatience) and low in the H scale performed better in the short-term memory task. Type A subjects had higher HR and performed better (faster RTs and higher scores) than Type Bs, but only while engaged in the cognitive task. The Type As also had higher SCs than Bs, although they were not differentiated according to task. Sub-scale patterns may have important implications for refining the Type A behavior concept.

An investigation of hemispheric asymmetry in size and semantic discriminations and related visual ERPs.

The present study examined possible hemispheric differences in discriminations of different sizes of geometric shapes (rectangles) and different meanings of words, and determined whether left and right hemisphere derived visual event related potentials (ERPs) were related to performance. Eighteen right-handed subjects (10 male and 8 female) participated in two separate sessions conducted on different days. The visual ERPs were recorded from over left parietal (P3) and right parietal (P4) scalp locations. Subjects were required to make discriminations of three words (PARE, PAIR, PEAR) and three sizes of rectangles (small, medium, large). Each word and rectangle was singly presented for 40 msec at 1 degree 24 minutes of arc to the left and right of central fixation (LVF and RVF respectively). The major findings were as follows: 1) there were no performance and ERP differences between hemispheres in the verbal task; 2) the left hemisphere excelled in the spatial task; however, ERPs derived from the two hemispheres were similar; 3) subjects experienced greater difficulty in their discriminations of geometric size, as compared to words, regardless of field of presentation. Discrimination of size seemed to have influenced P3 (P300) latency, i.e., it was longer (both hemispheres) when subjects made size discriminations as compared to words. It was proposed that the more difficult discriminations involved in size discrimination required a greater time for stimulus evaluation and that this was reflected in the delayed P3 response.

An investigation of hemispheric specialization and visual event related potentials in discriminations of line length.

The purpose of the present study was to examine possible hemispheric differences in discriminations of line length and to determine whether the visual event related potential (ERP) recorded from over left and right hemispheres was related to performance. Twelve right-handed subjects participated on each of 2 separate days. The visual ERPs were derived from left occipital (O1) and right occipital (O2) placements. Eye blinks and vertical and lateral eye movements were also monitored. A single vertical 1.0 cm line (Standard) was displayed for 40 ms and was followed 2 s later by either a 0.9 cm, 1.0 cm or 1.1 cm (Comparison) line (also 40 ms). Subjects were asked to judge whether the second of the lines (Comparison) was "shorter" or "longer" than the first. Stimuli appeared at the center of a screen or at 1 degree 24' to the left and right of central fixation. Accuracy of line length judgements were similar in all 3 visual fields indicating a lack of hemispheric performance asymmetry for this type of discrimination task. In addition, there was no evidence of hemispheric asymmetry in the ERPs. The ambiguous discrimination involving the 1.0 cm standard and comparison lines seems to have influenced P3 latencies at both hemispheres. Namely, P3 latency was significantly longer in response to the 1.0 cm line than to the 0.9 cm or 1.1 cm lines. We propose that the ambiguous discrimination required a greater time for simulus evaluation and that this was reflected in the delayed P3 latencies.

Hemispheric sex differences in response to apparently moving stimuli as indicated by visual evoked potentials.

This research was designed to determine whether visual event related potentials (ERPs) recorded from over the two occipital hemispheres would indicate differential processing of apparently moving and stationary stimuli. Previous findings in the literature led us to consider a male-female comparison as part of our experimental design. Nine male and nine female subjects were screened for right-handedness and visual abilities (acuity, depth and phoria). Each participated in three experimental sessions over a three day period in which ERPs were recorded from O1 and O2 in response to stimuli presented in left, central and right visual fields. The main finding was that, for female subjects, right hemispheric derived ERPs were larger in amplitude than left hemisphere recordings for apparently moving stimuli presented centrally. Males showed no hemispheric amplitude differences. However, for male subjects, the left hemisphere ERP latencies to motion were longer than those recorded from over O2 with central visual field presentations. It was speculated that different attentional strategies in the two sexes led to the observed result.