Integrating somatosensory information over time

Our choices are often informed by temporally integrating streams of sensory information. This has been well demonstrated in the visual and auditory domains, but the integration of tactile information over time has been less studied. We designed an active touch task in which subjects explored a spheroid-shaped object to determine its inclination with respect to the horizontal plane (inclined to the left or to the right). In agreement with previous findings, our results show that more errors, and longer decision times, accompany difficult decisions (small inclination angles). To gain insight into the decision-making process, we used a task in which the time available for tactile exploration was varied by the experimenter, in a trial-by-trial basis. The behavioral results were fit with a model of bounded accumulation, and also with an independent-sampling model which assumes no sensory accumulation. The results of model fits favor an accumulation-to-bound mechanism, and suggest that participants integrate the first 600 ms of 1800 ms-long stimuli. This means that the somatosensory system benefits from longer streams of information although it does not make use of all available evidence. Highlights The somatosensory system integrates information streams through time. Somatosensory discrimination thresholds decrease with longer stimuli. A bounded accumulation model is favored over independent sampling. Humans accumulate up to 600 ms, out of 1800 ms-long stimuli.