Costs and benefits of temporal expectations on somatosensory perception and decision-making

Our perception is shaped by prior expectations, including those about the timing of our sensations. These temporal expectations can be formed by recognizing patterns in the onset of sensory inputs. However, in the somatosensory domain, it remains unclear how these expectations impact the speed and accuracy of somatosensory judgments, as previous research has yielded mixed results. Here, participants used auditory tones to anticipate the onset of forces applied to their fingers and discriminated their intensity compared to a reference force. Experiment 1 showed that participants had worse discrimination sensitivity and higher thresholds for expected versus unexpected forces. Experiment 2 replicated and extended these costs to include perceptual accuracy, even when comparing expected to expectation-free forces, and further revealed reaction time benefits. Drift-diffusion modelling suggested that expectations speeded non-decisional processes while simultaneously slowing somatosensory evidence accumulation. These findings demonstrate both costs and benefits of temporal expectations in somatosensory perception and decision-making.