Tau and Kappa effects in physical space: the case of audition

The organization of spatio-temporal information in an auditory memory task was studied in two experiments. Stimuli consisted of four different configurations of eight sequentially presented beeps. In two configurations, the stimuli were space-time congruent, with (constant or variable) inter-stimulus distances corresponding to (constant or variable) inter-stimulus time intervals. In the other two configurations, the stimuli were space-time incongruent, with (constant or variable) inter-stimulus distances not corresponding to (variable or constant) inter-stimulus time intervals. After a learning phase consisting of 20 presentations of the target configuration, participants reproduced the spatial (Experiment 1) or temporal (Experiment 2) characteristics of the target 60 times in succession without re-examining the target configuration. Accuracy (with respect to the target) and variability (between responses) were found to evolve independently. In the incongruent space-time conditions, effects of variable inter-stimulus time intervals or distances on the reproduction of, respectively, constant distances (Tau effect) or constant time intervals (Kappa effect) were observed, while the reverse was not the case. Thus, dimensional interference occurred when the dimension to be ignored was variable. The results are discussed in the light of the distinction between properties of the stabilized mental image and the process of stabilization.