publications

2026

1. Martínez-López, P., León, J., Garre-Frutos, F., Vázquez-Millán, A., Molinero, S., Giménez-Fernández, T., Vadillo, M. & Luque, D. (2026). Habit learning and expression as stable traits. PsyArXiv. https://doi.org/10.31234/osf.io/ve3qf_v1

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   Individual differences in the capacity to learn and control habits are central to current models of psychopathology, which assume an overreliance on habit behavior in transdiagnostic compulsivity. However, whether these tendencies reflect stable, trait-like cognitive processes remains unclear. We examined the temporal stability of individual differences in habit learning and expression. Across two preregistered experiments, we assessed stimulus–response habits using the same stimuli after one day or different stimuli after four months. Evidence for stable individual differences in habit commissions was strong and comparable across experiments, indicating trait-like habit learning and expression. Improvements in response time across learning were stable and correlated with habits, suggesting an early trait-like index of habitualization. Stable processes of habit formation were reflected during both habit acquisition and expression.

2. Martínez-López, P., Garre-Frutos, F., Vadillo, M. & Luque, D. (2026). The Experimental Study of Habitual Behavior in Humans: A Review of the Validity of Current Protocols. PsyArXiv. https://doi.org/10.31234/osf.io/r62pa_v1

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   Although habits are widely recognized as playing a key role across psychological science, current laboratory methods may limit our understanding of these behaviors. Within the dual‑system framework, habits are defined as context-triggered, outcome‑insensitive responses that emerge gradually with repeated instrumental training. Many human experimental paradigms have been developed in an attempt to test this characterization of habits. However, in most cases, they have not provided clear evidence of habit formation, suggesting a gap between habit theory and existing methodologies. In the present study, we systematically review evidence on the construct validity of fourteen paradigms in which the amount of training was manipulated. We also reanalyze publicly available datasets from studies using these paradigms to assess the psychometric reliability of their main measures, thereby extending the available validity evidence. Paradigms that most closely mirror classical approaches derived from habit theory have consistently failed to induce habits, whereas more recent approaches have revealed training effects. However, these novel paradigms often rely on broader operationalizations that substantially diverge from traditional definitions of habit. Among the paradigms reviewed, the forced‑response task stands out as capable of inducing habitual behavior while providing a narrowly operationalized measure with acceptable reliability. Finally, we argue that strengthening the credibility of the field will require greater attention to the psychometric properties of habit measures, including precise operationalization, reliability, and systematic validity testing.

3. Garre-Frutos*, F., Martínez-López*, P., Ariza, A., Rey-Saez, R., Luque, D., Vadillo, M. & Felisa, G. (2026). Explicit knowledge modulates Pavlovian attentional biases. PsyArXiv. https://doi.org/10.31234/osf.io/uwge3_v2

   Abs preprint

   There is plenty of evidence showing that the history of stimulus-reward pairings can cause such stimuli to capture our attention more easily, even when attending to them actually prevents the delivery of a reward. Once established, these Pavlovian attentional biases are believed to operate automatically and persist even when they no longer predict a reward. This reflects an inflexible form of attentional sign-tracking. In this study, we investigated how reversal learning of Pavlovian attentional biases is affected by explicit knowledge. Across three experiments, we demonstrate that verbal instructions alone can modulate previously learned attentional biases (Experiments 1 and 2a) and that, when not informed of the reversal, participants still exhibit strong associations between Pavlovian attentional biases and individual differences in awareness of the new, reversed contingencies (Experiment 2b). Computational modelling of a previously published dataset reveals that instructions may prompt a rapid model-based revaluation by eliciting the automatic updating of the stimuli’s value representation. However, such updating can be counterproductive, as attending to the previously high-value distractor reduces the likelihood of receiving a reward when contingencies are re-evaluated. These findings emphazise the importance of explicit knowledge in the updating process.

4. Vázquez-Millán, A., Martínez-López, P., Rueda, M., León, J. & Luque, D. (2026). The evaluation of devaluation: Deficient outcome devaluation leads to wrongly considering goal-directed actions as habits. Behavior Research Methods, 58(1), 224. https://doi.org/10.3758/s13428-026-03099-6

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   Conceptualization, Methodology, Software, Investigation, Writing–review & editing

   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 has been documented in animal research but remains challenging to replicate in humans. Using a free-operant task, recent studies have suggested that human habits can be fully learned even after short training. This would produce a ceiling effect, explaining null results when the amount of training is manipulated. Here, we propose an alternative explanation: the devaluation protocol was ineffective for a subset of participants who appeared “habitual”. To test this hypothesis, we conducted a preregistered conceptual replication of the free-operant task with improved devaluation. As in previous research, we found no difference in habitual responses between short and extended training. In contrast to prior reports, most participants were sensitive to outcome devaluation. Habitual responding was strongly correlated with the effectiveness of the outcome devaluation protocol; habit-like responses were mostly produced by the few participants for whom the devaluation did not work. We further supported our hypothesis by reanalyzing previous datasets, finding that, across all studies, participants who showed more habit-like responses were those for whom the devaluation was less effective. Taken together, our findings suggest that suboptimal outcome devaluation protocols may have biased previous results, leading to habit-like goal-directed responses regardless of the amount of previous instrumental training.

5. 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), 7. 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

   Abs PDF CRediT

   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.