Simultaneous versus successive discrimination of weights: a neuroanatomical interpretation

Using the Method of Constant Stimuli, difference limens were obtained for lifted weights of 50 to 200 gm. 184 college students were assigned to one of four experimental conditions resulting from the combination of two modes of stimulus presentation with whether the preferred or non-preferred hand was used to judge the standard weight. Simultaneous interhand judgments produced significantly larger Weber Ratios and more variable Constant Errors than were produced by Successive intrahand presentation. This was contrary to earlier work in the visual modality indicating that simultaneous stimulus presentation produced more sensitive discrimination than did successive. The results are interpreted in terms of the neural organization of tactile input.