The degraded contingency test fails to detect habit induction in humans

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 unaffected 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.

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 unaffected 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.

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.

Methamphetamine (METH) induces neurotoxic changes, including partial striatal dopamine depletions, which are thought to contribute to cognitive dysfunction in rodents and humans. The dorsal striatum is implicated in action-outcome (A-O) and stimulus-response (S-R) associations underlying instrumental learning. Thus, the present study examined the long-term consequences of METH-induced neurotoxicity on A-O and S-R associations underlying appetitive instrumental behavior. Rats were pretreated with saline or a neurotoxic regimen of METH (4 × 7.5-10 mg/kg). Rats trained on random ratio (RR) or random interval (RI) schedules of reinforcement were then subjected to outcome devaluation or contingency degradation, followed by an extinction test. All rats then were killed, and brains removed for determination of striatal dopamine loss. The results show that: (1) METH pretreatment induced a partial 45-50% decrease in striatal dopamine tissue content in dorsomedial and dorsolateral striatum; (2) METH-induced neurotoxicity did not alter acquisition of instrumental behavior on either RR or RI schedules; (3) outcome devaluation and contingency degradation similarly decreased responding in saline- and METH-pretreated rats trained on the RR schedule, suggesting intact A-O associations guiding behavior; (4) outcome devaluation after training on the RI schedule decreased extinction responding only in METH-pretreated rats, suggesting impaired S-R associations. Overall, these data suggest that METH-induced neurotoxicity, possibly due to impairment of the function of dorsolateral striatal circuitry, may decrease cognitive flexibility by impairing the ability to automatize behavioral patterns.

Auditory cortex 2014 – towards a synthesis of human and animal research.

Instrumental learning in a mouse model for obsessive-compulsive disorder: Impaired habit formation in Sapap3 mutants

Succumb to habit: Behavioral evidence for overreliance on habit learning in Internet addicts

Conversation with Charles R. Schuster.

To investigate the involvement of dopaminergic projections to the prelimbic and infralimbic cortex in the control of goal-directed responses, a first experiment examined the effect of pretraining 6-OHDA lesions of these cortices. We used outcome devaluation and contingency degradation procedures to separately assess the representation of the outcome as a goal or the encoding of the contingency between the action and its outcome. All groups acquired the instrumental response at a normal rate, indicating that dopaminergic activity in the medial prefrontal cortex is not necessary for the acquisition of instrumental learning. Sham-operated animals showed sensitivity to both outcome devaluation and contingency degradation. Animals with dopaminergic lesions of the prelimbic cortex, but not the infralimbic cortex, failed to adapt their instrumental response to changes in contingency, whereas their response remained sensitive to outcome devaluation. In a second experiment, aimed at determining whether dopamine was specifically needed during contingency changes, we performed microinfusions of the dopamine D(1)/D(2) receptor antagonist flupenthixol in the prelimbic cortex only before contingency degradation sessions. Animals with infusions of flupenthixol failed to adapt their response to changes in contingency, thus replicating the deficit of animals with dopaminergic lesions in Experiment 1. These results demonstrate that dissociable neurobiological mechanisms support action-outcome relationships and goal representation, dopamine signaling in the prelimbic cortex being necessary for the former but not the latter.

The use of robots in experimental psychology and behavioral neuroscience is emerging as a fundamental method in behavioral experiments using animal models. Utilizing robots in animal experiments provides a substantial advantage for delivering specific stimuli to animals in a selective manner, teaching them different and relatively difficult behaviors, and manipulating group activity. In addition to using individual robots and animals together in behavioral paradigms, biohybrid organisms are created by integrating certain robotic systems with animals. Enabling animals to be controlled by external inputs like robots and enabling robots to be controlled by animals lead to the development of new experimental methods in behavioral animal studies. In addition, artificial intelligence and robotic learning models utilize animal behavior and basic working principles of the nervous system, and the emerging technology can be used in behavioral testing. This review investigates the use of robots and animals in experimental psychology and behavioral neuroscience under three headings. Behavioral tasks that contain animal-robot interactions (1) are discussed, together with biohybrid organisms created by integrating robots into the animals (2) and biology-inspired robotic systems (3). The theoretical and technical contributions of this novel technology and the resulting applications are evaluated. Keywords: Experimental psychology, behavioral neuroscience, animal models, robotics

AimAcute N‐methyl‐D‐aspartate (NMDA) receptor antagonism is an important pharmacological animal model of schizophrenia. In previous studies, schizophrenia patients show impaired goal‐directed behavior in an outcome‐specific devaluation procedure. In this study, we investigated whether the rat model of the NMDA receptor blockade also showed altered goal‐directed behavior in a satiety‐induced outcome devaluation paradigm.MethodsIn experiments 1 and 2, we aimed to establish the satiety‐induced outcome devaluation test using sucrose and lipid rewards in operant conditioning and free consumption paradigms. In experiment 3, we tested the effect of MK‐801 (0.1 mg/kg, i.p.) on outcome‐specific devaluation.ResultsExperiments 1 and 2 demonstrated that 1‐h ad libitum food consumption is sufficient to induce outcome‐specific devaluation in both lever‐press and free consumption tests in rats. Experiment 3 showed that the administration of MK‐801 impaired satiety‐induced devaluation in the lever‐press test but not in the subsequent free consumption test.ConclusionsOur results suggest that acute pharmacological NMDA receptor antagonism in rats is a useful animal model for impaired goal‐directed behavior in schizophrenia.

Adenosine A2A receptors (A2AR) in the dorsal striatum have been implicated in goal-directed behaviour. While activation of these receptors with several methods has resulted in an insensitivity to outcome devaluation, particular explanations for how they disrupt behaviour have not been explored. We both confirm a role for A2A receptors in goal-directed responding and evaluate additional behavioural aspects of goal-directed control to more fully understand the role of A2A receptors in instrumental behaviour. To examine the effects of the adenosine A2A agonist CGS-21680 in the DMS on response-outcome encoding, updating representations of outcome value and on the ability to inhibit behaviour when reward is not available. Male rats were trained to lever press for food reward. The A2AR agonist CGS-21680 was infused into the dorsomedial striatum either before an outcome devaluation test, prior to training with two distinct response-outcome associations or prior to a test of discriminative stimulus control over instrumental performance. Intra-DMS administration of CGS-21680 impaired sensitivity to outcome devaluation. CGS-21680 treatment did not impair acquisition of specific response-outcome associations, selective control of responding based on the presence of stimuli that signaled when reward was or was not available, discrimination between stimuli or lever choices nor did it influence the effect of devaluation on the amounts of food eaten in a consumption test. CGS-21680 impairs the ability to modulate responding based on recent changes to outcome value, an effect that is not accounted for by impairments in behavioural inhibition, discrimination, encoding the specific outcome of a response or the effectiveness of specific satiety.

Considerable evidence suggests that, in instrumental conditioning, rats learn the relationship between actions and their specific consequences or outcomes. The present study examined the role of the dorsomedial striatum (DMS) in this type of learning after excitotoxic lesions and reversible, muscimol-induced inactivation. In three experiments, rats were first trained to press two levers for distinct outcomes, and then tested after training using a variety of behavioural assays that have been established to detect action-outcome learning. In Experiment 1, pre-training lesions of the posterior DMS abolished the sensitivity of rats' instrumental performance to both outcome devaluation and contingency degradation when tested in extinction, whereas lesions of the anterior DMS had no effect. In Experiment 2, both pre-training and post-training lesions of the posterior DMS were equally effective in reducing the sensitivity of performance both to devaluation and degradation treatments. In Experiment 3, the infusion of muscimol into the posterior DMS selectively abolished sensitivity of performance to devaluation and contingency degradation without impairing the ability of rats to discriminate either the instrumental actions performed or the identity of the earned outcomes. Taken together, these results suggest that the posterior region of the DMS is a crucial neural substrate for the acquisition and expression of action-outcome associations in instrumental conditioning.

Studies of incongruent discrimination learning, where the outcome event of one response acts as the discriminative stimulus for the opposite response, suggest that humans rely on habitual stimulus-response (S-R) associations when outcome-response (O-R) associations would cause response conflict. Here, two experiments were conducted to investigate the robustness of this habitual strategy. In Experiment 1, we found that extensive instrumental discrimination training supported learning about the incongruent R → O contingencies, as assessed by an outcome devaluation test. Differential representations of the stimulus and the (associatively retrieved) outcome may have allowed for goal-directed incongruent performance. Experiment 2 failed to provide evidence for this possibility; direct presentation as well as associative retrieval of the incongruent events (by Pavlovian stimuli) activated the response that was associated with each event in its role of stimulus as opposed to outcome. We did find that participants successfully acquired explicit knowledge of the incongruent contingencies, which raises the possibility that propositional encoding allowed them to overcome the response conflict caused by O-R associations. Alternative associative and propositional accounts of successful goal-directed incongruent performance with extensive training will be discussed.

Synthesizing animal and human behavior research via neural network learning theory