Even distorted felt size engenders visual-haptic integration.

Intersensory interactions predicted by the sensory precision hypothesis have been infrequently examined by distorting the reliability of size perception by touch. Consequently, participants were asked to see one size and manually feel another unseen size either with bare fingers or with fingers sleeved in rigid tubes to decrease the precision of touch. Their subsequent visual estimates of the perceived size favored the more precise modality. Experiment 1 (N = 46) varied the intersensory discordance to examine whether the estimate arose from trivial response biases or from perceptual binding effects. Experiment 2 (N = 32) examined the presence of the perceptual effect in the absence of discordant sensory cues. Results favored a perceptual interpretation because the haptic and visual cues merged regardless of the discordance amount only when the stimulation arose from separate sources. The observed interaction between touch imprecision and visual bias is consistent with computational models of optimal perception.