Stimulus Distribution Shapes Color and Vibrotactile Perception.

Perception is shaped by both the physical properties of stimuli and their contextual presentation, often leading to systematic biases such as the central tendency effect, where perceptual judgments shift toward the average of the stimulus set. This study explored the central tendency bias in vibrotactile perception, an area that has received limited attention, while also replicating its well-documented occurrence in color perception to validate previous findings. Using a within-subjects design, participants (5 males, 15 females) completed color and vibrotactile discrimination tasks, each consisting of three blocks, which comprised systematically shifted stimulus sets. In an established virtual reality color task, stimuli ranged from yellow-green to blue-green, while in the vibrotactile task, stimuli varied in vibration intensity around a baseline distribution. As predicted, the point of subjective equality (PSE) shifted toward the mean of the stimulus sets in both tasks, confirming the presence of a central tendency bias. These findings demonstrate that perception of both color and vibrotactile intensity is not determined solely based on the physical properties of the stimulus per se, but it is rather influenced by the distribution of the presented stimuli, underscoring the pervasive role of contextual factors in shaping sensory judgments.Significance Statement Our senses do not work like measuring devices-they integrate incoming information with past experience and surrounding context. What we perceive can be biased toward the average of recently encountered stimuli, a phenomenon called the central tendency bias. Although this bias is well established in vision and hearing, it has never been directly tested for how we perceive touch intensity, despite the critical role of tactile information in daily activities and motor control. By determining whether touch perception is shaped by stimulus context, this research clarifies whether widely used tactile sensitivity measures reflect stable sensory thresholds or are influenced by prior experience. These findings have implications for experimental design, sensory assessment, and technologies that rely on accurate touch feedback.