It has been suggested that the two cerebral hemispheres play different roles in the maintenance and updating of an individual's beliefs. In particular it has been suggested that the left hemisphere (LH) forms consistent beliefs, whereas the right hemisphere (RH) monitors for inconsistencies or anomalies in reference to these beliefs. If some threshold of inconsistencies is detected, the role of the RH is to update the LH's belief system accordingly. Handedness may reflect the degree to which the two hemispheres exchange information such that the more strongly handed an individual is, the less interhemispheric communication may take place, thus attenuating this updating process. Two studies were carried out that confronted participants with conflicting, anomalous sensory information by tapping on both the participant's real hand and a fake hand in synchrony. One conclusion would be to update the LH belief system to include the fake hand as their own and consciously experience the taps as coming from the fake hand. It was predicted that this experience would vary with handedness such that the more strongly handed a participant was, the less they would experience the sensory illusion. Study 1 supported this, with more strongly handed participants reporting lesser degrees of the illusion. A second study replicated this effect and included a variable that measured the time it took for a participant to experience the illusion. A non-significant trend was present such that more strongly handed participants were slower to experience the illusion. Last, although the illusion was felt equally in both the left and right hand conditions, correlations between handedness and the illusion were only present in the left hand condition. A model of how interhemispheric interaction may function in maintaining beliefs and consciousness is presented.

Visual acuity and contrast sensitivity are two visual domains affected by normal aging; however, the potential impact of well-documented changes in these abilities on neuropsychological assessment is relatively unstudied. The current study examined the relationship between these abilities and neuropsychological performance in a healthy, community-based elderly sample. Fifty-one individuals (Age: M = 79.6) were assessed for visual acuity and visual contrast sensitivity, and received a brief neuropsychological battery. Results indicated contrast sensitivity was significantly related to neuropsychological performance on visually based measures, but not auditory measures. Visual acuity was only weakly related to neuropsychological performance. Clinical implications for assessment of elderly individuals are discussed.

The Medical Symptom Validity Test (MSVT) was administered as part of a neuropsychological battery to a mixed clinical sample of 286 consecutively referred individuals. Of the 47% of the sample who failed in the easy subtests, 48% were considered to have the "dementia profile." The remaining 52% of individuals failing the easy subtests were considered by the task to have "poor effort." Comparing the neuropsychological test performance among these three groups (Pass, Dementia Profile, Poor Effort) found that on most tasks those individuals passing the easy subtests of the MSVT perform significantly better than the other two groups, which did not differ from each other. Individuals meeting criteria for the Dementia Profile performed worse on tasks of motor functioning and list learning in comparison to the Poor Effort group. The results suggest that the algorithm creating a Dementia Profile does not effectively differentiate groups of individuals who fail the easy subtests of the MSVT. Consideration of a more liberal cutoff score for the easy subtests is offered.

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