Space-time interactions and the perceived location of cold stimuli

The objective of this experiment was to determine whether illusions of space and time that have been demonstrated for mechanical stimulation on the skin also occur for thermal stimuli within the innocuous range of temperatures. Four cooling pulses were presented on the forearm in varying spatial and temporal sequences. Participants indicated the perceived location of the first two pulses in the four-pulse sequence after each trial. The results indicate that the position of the second pulse changed substantially in the direction of the third pulse when the interval between the pulses was brief (0.2 s) and the distance between the second and third pulse was larger. At longer intervals and shorter distances there was no change in perceived location. These findings demonstrate that the tau effect does occur with thermal stimuli, and that the temporal interval between thermal stimuli applied to the skin can influence their perceived location.