Date of Graduation

5-2026

Document Type

Thesis

Degree Name

Bachelor of Science in Mechanical Engineering

Degree Level

Undergraduate

Department

Mechanical Engineering

Advisor/Mentor

Jenn Campbell

Committee Member

Anthony Gunderman

Abstract

Brain activity in pain-related regions of the cortex is thought to be influenced by interactions between expectations and incoming sensory information. However, the subjective experience of pain based on expectation has not been thoroughly explored. By changing visual and auditory cues to set expectation levels, a relationship between unconscious expectation of pain and actual sensory pain experienced was characterized. With IRB approval, volunteers were randomly and blindly grouped into low and high pain expectancy groups. Each group completed a survey about initial pain expectations before the muscle stimulation tolerance test, followed by a survey about actual pain perception after the test. A TENS (transcutaneous electrical nerve stimulator) unit was used to induce low levels of pain through muscle stimulation. The electrodes were placed on the right bicep of the participant and intensity increased every 15 seconds until the participants reported they had hit their pain threshold and tolerance. The maximum time of exposure was  limited to 300 seconds for the safety of the participant. The findings revealed that men in the low expectation group reported experiencing significantly higher levels of pain, whereas women in the same group demonstrated a significantly higher pain threshold and tolerance. Additionally, men exhibited a higher pain threshold and tolerance compared to women; however, this difference was correlated with a significantly larger bicep diameter in men. Further analysis indicated that bicep diameter had a notable effect on pain threshold. The results provide insight into how positive expectations can lead to decreased pain felt in chronic disorders and diseases, potentially reducing opioid need.

Keywords

Pain perception; pain tolerance; pain threshold; expectation; human factors

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