publications

2026

1. Martínez-López, P., Vázquez-Millán, A., Garre-Frutos, F. & Luque, D. (2026). Assessing the validity evidence for habit measures based on time pressure. Behavior Research Methods, 58(1). https://doi.org/10.3758/s13428-025-02865-2

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   Conceptualization, Methodology, Software, Investigation, Data curation, Formal analysis, Validation, Visualization, Writing–original draft

   Animal research has shown that repeatedly performing a rewarded action leads to its transition into a habit—an inflexible response controlled by stimulus–response associations. Efforts to reproduce this principle in humans have yielded mixed results. Only two laboratory paradigms have demonstrated behavior habitualization following extensive instrumental training compared to minimal training: the forced-response task and the “aliens” outcome-devaluation task. These paradigms assess habitualization through distinct measures. The forced-response task focuses on the persistence of a trained response when a reversal is required, whereas the outcome-devaluation task measures reaction time switch costs—slowdowns in goaldirected responses conflicting with the trained habit. Although both measures have produced results consistent with the learning theory—showing stronger evidence of habits in overtrained conditions—their construct validity remains insufficiently established. In this study, participants completed 4 days of training in each paradigm. We replicated previous results in the forced-response task; in the outcome-devaluation task, a similar pattern emerged, observing the loss of a response speed advantage gained through training. We then examined the reliability of each measure and evaluated their convergent validity. Habitual responses in the forced-response task and reaction time switch costs in the outcome-devaluation task demonstrated good reliability, allowing us to assess whether individual differences remained stable. However, the two measures were not associated, providing no evidence of convergent validity. This suggests that these measures capture distinct aspects of the balance between habitual and goal-directed control. Our results highlight the need for further evaluation of the validity and reliability of current measures of habitual control in humans.

2025

1. Molinero, S., Martínez-López, P., Morís, J., Quintero, M., Cobos, P., López, F. & Luque, D. (2025). The degraded contingency test fails to detect habit induction in humans. PLoS One, 20(10), e0334087. https://doi.org/10.1371/journal.pone.0334087

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   Methodology, Software, Investigation, Data curation, Formal analysis, Validation, Visualization, Writing – review & editing

   In experimental psychology and behavioral neuroscience, habits are considered stimulus-response (S-R) associations formed through extended reward training. Accordingly, habits are assessed using one of two tests: 1) Outcome devaluation, in which the value of the outcome (reward) is reduced, making it less desirable, and 2) Contingency degradation, in which the response-outcome association is reversed so that responding prevents the delivery of a reward. If a behavior is controlled by S-R links, then it should remain mostly insensitive by these two manipulations. Animal research using the outcome devaluation test has shown that initially goal-directed actions can become habitual after extended operant training. However, replicating this transition in human research has proven challenging, representing a significant problem for translational research. Notably, the contingency degradation test has rarely been used in human research. In this study, we aimed to demonstrate a shift from goal-directed to habitual control through three pre-registered experiments. Participants were trained in two S-R-O (stimulus-response-outcome) mappings for three days, with one condition (the ‘overtrained’) occurring four times more frequently than the other (‘standard’). Importantly, we assessed the habitualization of both responses by using a degraded contingency test. Overall, we found no evidence of an overtraining effect — that is, the ‘overtrained’ condition did not lead to increased habitual responding. We discuss the theoretical and applied implications of these findings and explore further directions for studying habitual behavior.

2. Vázquez-Millán, A., Martínez-López, P., Rueda, M., León, J. & Luque, D. (2025). (preprint) Habits Need Time: Evidence of Habit-like Behavior After Short Training Likely Reflects Failures in Habit Testing. PsyArXiv. https://doi.org/10.31234/osf.io/zh39t_v1

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   Habits are stimulus-driven responses that are produced independently of the current outcome value. They enable efficient actions in familiar contexts while freeing up cognitive resources. Habits are expected to influence behavior after substantial experience, whereas limited training leaves behavior under goal-directed control. This transition from goal-directed to habitual control is well-documented in animal research but remains challenging to replicate in humans. Recent studies have suggested that human protocols are so effective at inducing habitual control that habits can appear even after short training, thereby masking the training effects. These studies typically test habits by reducing outcome value (e.g., food, through satiation) and report persistent habit-like behavior in minimally trained participants. Here, we propose an alternative explanation: we think that the devaluation protocol was ineffective for this subset of ‘habitual’ participants. To test this hypothesis, we conducted a pre-registered experiment using the same task but with monetary rewards instead of food, hypothesizing that money can be more effectively devalued and avoid the social issues associated with eating. We found no difference in habitual responses between short and extended training. In contrast to prior reports, most participants were sensitive to outcome devaluation. We further supported our hypothesis by reanalyzing previous datasets, finding that across all studies (including ours), participants showing more habit-like responses were those for whom the devaluation was less effective. We discuss the theoretical and methodological implications of these findings.