Generalization of conditioned fear along a dimension of increasing fear intensity

Abstract

The present study investigated the extent to which fear generalization in humans is determined by the amount of fear intensity in nonconditioned stimuli relative to a perceptually similar conditioned stimulus. Stimuli consisted of graded emotionally expressive faces of the same identity morphed between neutral and fearful endpoints. Two experimental groups underwent discriminative fear conditioning between a face stimulus of 55% fear intensity (conditioned stimulus, CS+), reinforced with an electric shock, and a second stimulus that was unreinforced (CSÀ). In Experiment 1 the CSÀ was a relatively neutral face stimulus, while in Experiment 2 the CSÀ was the most fear-intense stimulus. Before and following fear conditioning, skin conductance responses (SCR) were recorded to different morph values along the neutral-to-fear dimension. Both experimental groups showed gradients of generalization following fear conditioning that increased with the fear intensity of the stimulus. In Experiment 1 a peak shift in SCRs extended to the most fear-intense stimulus. In contrast, generalization to the most fear-intense stimulus was reduced in Experiment 2, suggesting that discriminative fear learning procedures can attenuate fear generalization. Together, the findings indicate that fear generalization is broadly tuned and sensitive to the amount of fear intensity in nonconditioned stimuli, but that fear generalization can come under stimulus control. These results reveal a novel form of fear generalization in humans that is not merely based on physical similarity to a conditioned exemplar, and may have implications for understanding generalization processes in anxiety disorders characterized by heightened sensitivity to nonthreatening stimuli.

Conditioned Fear Acquisition and Generalization in Generalized Anxiety Disorder

“…More importantly, whereas high arousal could be associated with PD, decreased arousal seems to characterize GAD (Hoehn-Saric, McLeod, & Zimmerli, 1989;Hoehn-Saric, McLeod, Funderburk, & Kowalski, 2004). Previous studies suggest that fear sensitization (i.e., an enhanced fear response after experiencing intense fear) plays an important role in conditioned fear-generalization (Dunsmoor, Mitroff, & LaBar, 2009). Given that increases in general arousal may sensitize some fear-relevant stimuli (see, for example, Öhman & Mineka, 2001), it is therefore possible that only anxiety disorders characterized by increased arousal show augmented conditioned fear-generalization.…”

“…This is important given the effects that differential fear acquisition may have on conditioned fear-generalization (see Dunsmoor, Mitroff, & LaBar, 2009). …”

“…However, generalization may also occur along a dimension of fear intensity. In fact, a recent study suggests that generalization of conditioned fear in humans is determined by fear intensity rather than physical similarity (Dunsmoor, Mitroff, & LaBar, 2009). It could be the case that GAD (or other anxiety disorders) is characterized by abnormalities in conditioned fear-generalization determined by the former rather than the latter.…”

Fear Generalization in Humans: Systematic Review and Implications for Anxiety Disorder Research

“…The contribution between perceptual similarity and emotional intensity on fear generalization was examined by Dunsmoor et al (2009) using a stimulus dimension of morph increments of the same facial identity but displaying varying intensity of emotional expression. A face with a high degree of fearful expression intensity and a face with a neutral expression served as endpoints along a fear expression intensity continuum.…”

“…This generalization of conditioned fear shows that CRs are often elicited by stimuli not associated with the aversive event but which resemble the CS along a formal, perceptual dimension (Honig & Urcuioli, 1981). The study of stimulus generalization processes like this has a long history of research in both Pavlovian and instrumental/operant conditioning (e.g., Hull, 1943;McLaren & Mackintosh, 2002;Pavlov, 1927), but has only recently been extended to fear generalization in humans (Dunsmoor, Mitroff, & LaBar, 2009;Lissek et al, 2008Lissek et al, , 2010Vervliet, Vansteenwegen, Baeyens, Hermans, & Eelen, 2005;Vervliet, Vansteenwegen, & Eelen, 2004).…”