The Influence of Negative Expectancies on Itch-related Avoidance Behavior

Itch expectancies play a key role in itch perception and may elicit avoidance behaviors to prevent itch, even when it is costly. Despite theoretical evidence that expectancies can influence avoidance behaviors, no studies have empirically investigated their association in the context of itch. The aim of this study was to investigate whether negative expectancy manipulation led to more costly itch-related avoidance behavior.

This study was conducted using a within-subjects repeated measures experimental design. Thirty-four participants underwent an instructional learning and conditioning procedure in which a sham experimental solution paired with a "high" quantity of cowhage spicules was used to induce high itch-expectations. A control solution paired with a medium quantity of cowhage spicules was used to induce medium itch-expectations. Subsequently, participants learned that by effortfully gripping a dynamometer above a certain level, they could avoid strong itching. In anticipation of two other itch stimuli after reapplication of the experimental solution and the control solution, average grip strength (reflecting costly itch-avoidance behavior) was measured.

Results indicated that negative itch expectations were successfully induced (p < 0.001, d = 1.16). However, while participants engaged in avoidance behavior in both experimental and control trials, negative expectancy learning did not lead to more costly avoidance behavior (p = 0.74, ηp2 = 0.003).

Results suggested that acute itch induced avoidance behavior regardless of expectations toward itch. Extending the research on the role of avoidance and its impact on itch may shed light on new approaches for itch management.