Individual differences in the influence of task-irrelevant Pavlovian cues on human behavior.

Sara Garofalo,Giuseppe Di Pellegrino

doi:10.3389/fnbeh.2015.00163

Sara Garofalo, Giuseppe Di Pellegrino

Open Access

https://doi.org/10.3389/fnbeh.2015.00163

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Abstract

Pavlovian-to-instrumental transfer (PIT) refers to the process of a Pavlovian reward-paired cue acquiring incentive motivational proprieties that drive choices. It represents a crucial phenomenon for understanding cue-controlled behavior, and it has both adaptive and maladaptive implications (i.e., drug-taking). In animals, individual differences in the degree to which such cues bias performance have been identified in two types of individuals that exhibit distinct Conditioned Responses (CR) during Pavlovian conditioning: Sign-Trackers (ST) and Goal-Trackers (GT). Using an appetitive PIT procedure with a monetary reward, the present study investigated, for the first time, the extent to which such individual differences might affect the influence of reward-paired cues in humans. In a first task, participants learned an instrumental response leading to reward; then, in a second task, a visual Pavlovian cue was associated with the same reward; finally, in a third task, PIT was tested by measuring the preference for the reward-paired instrumental response when the task-irrelevant reward-paired cue was presented, in the absence of the reward itself. In ST individuals, but not in GT individuals, reward-related cues biased behavior, resulting in an increased likelihood to perform the instrumental response independently paired with the same reward when presented with the task-irrelevant reward-paired cue, even if the reward itself was no longer available (i.e., stronger PIT effect). This finding has important implications for developing individualized treatment for maladaptive behaviors, such as addiction.

Highlights

Goal-directed behavior can be variably influenced by external and internal factors which impact the values and priorities assigned to rewards and goals (Doya, 2008)
ST and GT Conditioned Responses (CR) To ensure that the oculomotor responses used to categorize ST and GT individuals were learned CRs, eye-gaze indices were separately analyzed for CS+ and CS− trials in the first and second halves of the Pavlovian Conditioning task
Results from CS− trials did not show any significant effects. These results indicate two important points: first, a bias toward either the Sign or the Goal is a learned CR, since it is not present at the beginning of the task but emerges later in time, when contingencies have been learned (Figure 2A); this looking bias is specific to the reward-paired cue (CS+), as no differences were observed for the unpaired cue (CS−; Figure 2B)

Summary

Introduction

Goal-directed behavior can be variably influenced by external and internal factors which impact the values and priorities assigned to rewards and goals (Doya, 2008). One of the most simple and effective mechanisms for influencing choice is reinforcement learning. Given the complexity of the animal’s environment, learning that an arbitrary cue (e.g., a sound) is predictive of a certain goal (e.g., obtain a reward, such as food), allows the animal to learn a flexible response that facilitates achievement of the goal itself. In most cases such cue-controlled behavior is adaptive; for example it helps one obtain food when hungry (Perks and Clifton, 1997; Holmes et al, 2010). An inflexible association can lead to perseverance in the same choice

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