Simultaneous versus successive discrimination of weights: a neuroanatomical interpretation

Effects of colored light and colors of comparison stimulus and their background on heaviness of lifted weight

The effects of colored light and colors of stimuli and their backgrounds on participants' perceptions that the weight of a stimulus was identical to a standard weight were examined. A total of 23 women and 19 men, Taiwanese college students ages 20 to 23 years (M = 21.2, SD = 0.8) were randomly divided into three groups, with each assigned to one of three possible colored light conditions. Colored light significantly affected the constant errors between weight perceptions of the comparison and standard stimuli; the perception constant errors under yellow light were significantly less than those under red and blue lights, and the constant errors under red light were less than those under blue light. Stimulus color significantly affected the constant errors, which were significantly greater for white, yellow, red, and blue comparison stimuli than for black stimuli; the constant errors were significantly greater for white and yellow stimuli than for red and blue. Moreover, an interactive two-way effect of stimulus color and colored light was detected; however, no significant effect of color of stimulus background on constant error was observed. Practical applications include development of safe lifting guidelines and package and product design.

Different pattern of hemisphere specialization between identical kinesthetic spatial and weight discrimination tasks

Thumb position discrimination and weight discrimination tasks were examined in female students. Task procedures were identical for the position and weight tasks. Different weights were loaded for each positioning and the thumb was abducted to discriminate the weight. The Weber ratio was obtained by the method of constant stimuli and was compared between right and left. The results of position discrimination indicated left thumb (right hemisphere) superiority, while the results of weight discrimination indicated no laterality despite identical tasks. Directed attention is suggested to play an important role in the appearance of hemisphere lateralization.