Abstract:  Women are more susceptible to disorders of fear and anxiety than men, with the prevalence of posttraumatic stress disorder (PTSD) two-to three-fold higher in women. Whereas normal fear responses are triggered by trauma-associated cues, in disorders such as PTSD, fear is also elicited in neutral or safe cues. Hence, fear over-generalization has been put forward as a potential etiological factor of PTSD and other anxiety disorders. Therefore, in this study, we examined whether women show stronger fear generalization than men, and are there any differences between women and man in the extinction of fear generalization. The answers to such questions could provide a new perspective on the severe prevalence of anxiety disorders in women. Forty-five college students participated in this study. Three participants’ data were deleted for technical failure, leaving forty-two participants’ (Female: 22, Male: 20) data in analysis finally. The experiment consisted of two phases: acquisition, and generalization. 10 rings of gradually increasing size were served as conditioned stimuli (CS) and generalization stimuli (GS). The rings in the two extreme sizes were as the conditioned danger cue (CS+) and conditioned safety cue (CS−), respectively. The eight intermediately sized rings were served as four classes of generalization stimuli (i.e., GS1, GS2, GS3, and GS4), with GS4 being the most similar one to CS+ in size. A 500ms-electric stimulus served as unconditioned stimulus (US). CS+ was probably paired with US, while CS− and GS were unpaired with US. During the experiment, US online expectancy ratings and skin conductance responses (SCR) were recorded. The results showed that women had longer extinction duration of fear generalization than men, while there were no sex differences in generalization gradient. Such results were proved in the indexes of both online expectancy ratings and SCR. In the index of online expectancy ratings, both women and men generalized fear into GS3 and GS4. In the fear extinction of GS3, there were no sex difference and both genders extinguished generalized fear in Block3. As for GS4, women extinguished fear from Block5 while males were from Block3, which indicted that women need more time in generalization extinction. The conclusions above were also found in SCR. Both women and men transferred fear to GS4, but there had sex differences in the extinction of fear generalization. Men extinguished the fear of GS4 from Block3, while women were from Block4. The results of SCR also indicated that the women had longer extinction duration of fear generalization than men. The theory of behavioral inhibition was supported by this study, for the sex differences of fear generalization only occurring in generalization extinction but not generalization gradient. Given the role of fear generalization in anxiety disorders, our findings suggest that longer generalization extinction may contribute to the higher risk of anxiety disorders in women. Additionally, our findings also have potential value for treatments of anxiety disorders among women in clinical.

Key words: fear generalization, generalization extinction, sex differences