SOMATOSENSORY ATTENUATION DOES NOT DIFFER ACROSS EFFECTOR–RECEPTOR FINGER PAIRINGS

Self-generated touch (e.g., touching the left hand with the right hand) is perceived as less intense than an identical touch delivered externally (by another person or a machine). This phenomenon, termed somatosensory attenuation, reflects reduced perceptual and neural responses to self-generated touch and is thought to arise from an internal forward model that uses an efference copy of the motor command to predict sensory consequences.
Previous research has almost exclusively examined attenuation for touch generated by, and applied on, the index finger. Thus, it remains unclear whether attenuation varies across different effector–receptor finger pairings. Because forward models rely on prior sensorimotor experience, attenuation might depend on learned effector–receptor mappings. Fingers differ in motor individuation, grasp control, spatial acuity, and cortical representation, suggesting that sensory predictions could differ across fingers. Alternatively, attenuation may reflect a basic low-level sensorimotor process that does not require fine-tuning.
We tested this hypothesis in two preregistered experiments. In Experiment 1, participants used their right index finger to touch different receptor fingers on the left hand (thumb, index, middle, ring, little). In Experiment 2, participants touched their left index using different effector fingers of the right hand (thumb, index, middle, ring, little). In line with our preregistered hypotheses, we observed significant somatosensory attenuation for all receptor fingers (Experiment 1) and for all effectors (Experiment 2), with no significant differences between fingers. Bayesian analyses provided moderate-to-strong evidence for the absence of finger-related differences. Therefore, these results suggest that somatosensory attenuation generalises across effector and receptor fingers.