Spatial and temporal factors in the discrimination of lifted weights

Abstract

In a series of experiments investigating spatial and temporal factors in the discrimination of lifted weights, differential thresholds (DLs) were measured. The temporal factor, known as the time-order error, was found to be negative in one-handed and two-handed consecutive discrimination paradigms, and at low and high stimulus intensities. The spatial factor, known as the space—error, was found to produce a strong bias in a two-handed simultaneous discrimination paradigm. The direction of the bias did not correlate with hand preference or attentional factors but with sex; with weights appearing lighter in the preferred hand of males and heavier in the preferred hand of females. Other spatial factors, such as hand, hemispace and method of lifting were found to affect DLs. Surprisingly DLs for the preferred hand were not necessarily lower than DLs for the non-preferred hand. The preferred ear provided a more reliable indication of hand advantage by specifying to which cerebral hemisphere language was probably lateralised. The hand contralateral to the non-language (spatial) hemisphere revealed an advantage in weight discrimination. Left-handed subjects were found to perform better than right handed subjects with their preferred hand. This was explained by the fact that a higher proportion of left-handed subjects have their preferred hand contralateral to the spatial hemisphere. DLs were found to be lower in the hemispace contralateral to the spatial processing hemisphere tor both right and left hands. It was concluded that weight discrimination should be considered as a manipulospatial activity subserved by higher order functioning of the cerebral hemisphere contralateral to the hand used in lifting the weight and contralateral to the spatial field within which the weight was lifted.