Ambiguous or blunted responses to sensory and painful stimuli among individuals with severe intellectual disabilities and co-morbid communicative impairments put them at risk for having their experience of pain discounted and their expression of pain misinterpreted. Valid measurement procedures of behavioral expression are critical for this vulnerable group of individuals. We investigated a sham-controlled sensory testing protocol as an approach to guard against observer bias during non-verbal behavioral recording for individuals with intellectual disabilities. Participants were 44 (52% male) adults (mean age = 46, sd = 10) with moderate (14%) and severe to profound (86%) intellectual impairment. The facial behavior of the participants before, during, and after five sensory stimulation modalities (pin prick, light touch, deep pressure, cool, warm) was coded by three raters using the Facial Action Coding System (FACS). For each participant, their 5 active sensory trials were randomized with sham trials during which no stimulation was applied. Observers were blinded to active vs. sham stimulation status. FACS scores increased significantly during active sensory trials (p < 0.05) compared with sham trials. There were significant effects for gender with females more expressive than males (p < 0.05). There were also significant effects for the presence of self-injurious behavior (SIB) with individuals with SIB more expressive than individuals without SIB (p < 0.05). The results suggest that the procedure was valid (i.e., distinguished between active vs. sham sensory stimulation) and provides additional evidence that individuals with significant intellectual impairments are sensitive to tactile stimulation consistent with quantitative sensory testing protocols
