Can experimentally induced positive affect attenuate generalization of fear of movement-related pain?

Recent experimental data show that associative learning processes are involved not only in the acquisition but also the spreading of pain-related fear. Clinical studies suggest involvement of positive affect in resilience against chronic pain. Surprisingly, the role of positive affect in associative learning in general and in fear generalization in particular has received scant attention. In a voluntary movement paradigm, in which one arm movement (CS+) was followed by a painful stimulus and another was not (CS-), we tested generalization of fear to five novel but related generalization movements (GSs; within-subjects) after either a positive affect induction or a control exercise (Group = between-subjects) in healthy participants (N = 50). The GSs' similarity with the original CS+ movement and CS- movement varied. Fear learning was assessed via verbal ratings. Results indicated that there was an interaction between the increase in positive affect and the linear generalization gradient. Stronger increases in positive affect were associated with steeper generalization curves due to relatively lower pain-US expectancy and less fear to stimuli more similar to the CS-. There was no Group by Stimulus interaction. Results thus suggest that positive affect may enhance safety learning through promoting generalization from known safe movements to novel yet related movements. Improved safety learning may be a central mechanism underlying the association between positive affect and increased resilience against chronic pain. PERSPECTIVE: We investigated to which extent positive affect influences the generalization (i.e., spreading) of pain-related fear to situations similar to the original, pain-eliciting situation. Results suggest that increasing positive affect in the acute pain stage may limit the spreading of pain-related fear, thereby potentially inhibiting transgression to chronic pain conditions.