Abstract
The effect of stress on the balance between goal-directed behavior and stimulus–response habits has been demonstrated in a number of studies, but the extent to which stressful events that occur during development affect the balance between these systems later in life is less clear. Here, we examined whether individuals with a history of early-life stress (ELS) show a bias toward avoidance habits on an instrumental learning task as adults. Participants (N = 189 in Experiment 1 and N = 112 in Experiment 2) were undergraduate students at the University of California, Los Angeles. In Experiment 1, we hypothesized that a history of ELS and a longer training phase would be associated with greater avoidance habits. Participants learned to make button-press responses to visual stimuli in order to avoid aversive auditory outcomes. Following a training phase involving extensive practice of the responses, participants were tested for habitual responding using outcome devaluation. After completing the instrumental learning task, participants provided retrospective reports of stressful events they experienced during their first 16 years of life. We did not observe evidence for an effect of the length of training, but we did observe an effect of ELS, with greater stress predicting greater odds of performing the avoidance habit. In Experiment 2, we sought to replicate the effect of ELS observed in Experiment 1, and we also tested whether the presence of distraction during training would increase avoidance habit performance. We replicated the effect of ELS but we did not observe evidence of an effect of distraction. Taken together, these data lend support to the hypothesis that stress occurring during development can have lasting effects on the balance between goal-directed behavior and stimulus–response habits in humans. Enhancement of avoidance habits may help explain the higher levels of negative health outcomes such as heart and liver disease that have been observed in individuals with a history of ELS. Some of the negative health behaviors that contribute to these negative health outcomes, e.g., overeating and substance use, may be performed initially to avoid feelings of distress and then transition to being performed habitually.
Highlights
The effects of stress on physical and psychological health have been of increasing interest in recent years, with one area of focus being how individuals are affected by stress that occurs during development
Because many negative health outcomes are linked to repetitive behaviors such as overeating or substance use, it is possible that an increased reliance on stimulus–response habits in this population could explain some of the health effects experienced by its constituents
Selective responding to the still-valued stimulus indicates that participants have flexibly adjusted their behavior, whereas persistence in responding to the devalued stimulus despite the built-in cost to performance that results from continuing to hold in mind a rule that no longer applies and executing unnecessary behaviors on the basis of this rule is interpreted as habitual behavior
Summary
The effects of stress on physical and psychological health have been of increasing interest in recent years, with one area of focus being how individuals are affected by stress that occurs during development (early-life stress, ELS). In a pair of studies conducted by Gillan et al (2014, 2015), a shock avoidance task incorporating a novel procedure for devaluation of aversive outcomes was used to investigate avoidance habits In this task, participants learned to avoid electric shocks delivered to the left and right wrist by making responses to warning stimuli with the left and right foot, respectively. Selective responding to the still-valued stimulus indicates that participants have flexibly adjusted their behavior (i.e., that they are behaving in a goal-directed manner), whereas persistence in responding to the devalued stimulus despite the built-in cost to performance that results from continuing to hold in mind a rule that no longer applies and executing unnecessary behaviors on the basis of this rule is interpreted as habitual behavior Using this procedure, Gillan et al (2014, 2015) demonstrated enhanced avoidance habits in individuals with obsessive-compulsive disorder. The secondary hypotheses were (a) that individuals who received a greater level of training prior to devaluation would show enhanced avoidance habits relative to those who received less training, and (b) that learning the stimulus–response associations in the presence of distraction would lead to enhanced avoidance habits relative to associations learned without distraction
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