Increased electrodermal responding to all conditional stimuli during reinstatement test: Generalized fear or sensitization?

Fear conditioning experiments commonly use reinstatement manipulations to investigate processes underlying the return of fear. Current literature describes two types of reinstatement, generalized and differential. Both response patterns are currently interpreted to indicate return of fear. This study questions whether the response pattern referred to as 'generalized reinstatement' indeed signifies return of fear and provides an alternative interpretation. Across three datasets we show that 'generalized reinstatement' is not due to the generalization of fear across conditioned stimuli (CSs). By comparing electrodermal and self-report data (CS evaluations and unconditional stimulus (US) expectancies) as a function of the CS trial sequence at reinstatement test, this research shows that fear does not generalized across CSs. The current findings identify 'generalized reinstatement' as a misnomer as increased electrodermal responses to all conditional stimuli cannot be taken as a sign for return and generalization of fear but may rather reflect sensitization. We suggest the use of "non-specific reinstatement" as a replacement term for "generalized reinstatement" to avoid the impression that fear has generalized across CSs. Moreover, this research highlights the importance of collecting self-report together with physiological responses for more in-depth interpretation.