Learned industriousness as a translational mechanism in anorexia nervosa

Abstract

It remains unexplained why some behaviours persist despite being non-hedonic and ostensibly aversive. This phenomenon is especially baffling when such behaviours are taken to excess in the form of psychopathology. Anorexia nervosa is one psychiatric disorder in which effortful behaviours that most people find unpleasant (suchas restrictive eating) are persistently performed. We propose thatthe social psychology theory of learned industriousness providesa novel mechanistic account for such phenomena. This theoryposits that high-effort behaviour can be conditioned to acquire secondary reinforcing properties through repeated pairing with reward. Accordingly, effort sensations become less aversive andmore appetitive, increasing willingness to engage in effortful behaviour. In this Perspective, we review pre-clinical behaviouraland biological data that support learned industriousness, contrast learned industriousness with other models of non-hedonic persistence (such as habit learning), highlight evidence that supports learned industriousness in individuals with anorexia nervosa and consider implications of the model, including translation to other psychiatric presentations.

Introduction

It has baffled behavioural economists and mental health professionals that some individuals persistently engage in behaviours that are not conventionally rewarding or that are ostensibly aversive. More than two decades ago, mountaineering was used to illustrate this type of persistent behaviour: certain individuals become strongly compelled to mountain climb under treacherous, life-threatening conditions¹. Yet, diaries documenting mountaineering expeditions suggest that the momentary experience of mountaineering is neither enjoyable nor thrilling, but is instead rather unpleasant, lonely and tedious¹. Additional examples of this type of persistent effortful behaviour include overly abstemious financial practices², excessive work pursuits³ and even extreme competitive birding⁴. Although these four examples differ in many ways, they all describe activities that require substantial difficulty, that most individuals find unpleasant and that certain individuals engage in repeatedly and to excess. However, insight into the processes that maintain over-engagement in such seemingly costly behaviours remains elusive.

These persistent behaviours have corollaries with some psychiatric illnesses, including anorexia nervosa, an eating disorder characterized by an individual’s persistent engagement in weight-control behaviours to override their biological drive to eat, which eventually leads to severe deficiency in caloric energy intake (starvation)⁵. For individuals with the restricting subtype of anorexia nervosa, such weight-control behaviour involves continuous caloric restriction. For other individuals with the binge eating/purging subtype of anorexia nervosa, extreme caloric restriction is punctuated by intermittent binge eating and/or purging episodes. Certain behaviours of individuals with anorexia nervosa, such as restrictive eating and excessive exercising, require intensification of physical effort (tolerating hunger, fatigue and discomfort) and cognitive effort (for instance, tracking caloric intake or fitness output) for lengthy periods before the presumed desired outcome — weight loss — is obtained. Other eating disorder behaviours, such as self-induced vomiting or fasting, require toleration of shorter-term, but more intense physical effort (for instance, the acute difficulty of causing the body to vomit or deny all food).

Although almost all individuals will attempt to alter their diet and exercise levels to manage their weight at some point in their lifetime⁶, most individuals find this experience unpleasant. Adherence to weight-control behaviours can limit access to the physical and social rewards (such as the tastiness of food and social celebrations surrounding food) associated with consuming palatable foods and requires endurance of adverse effects of caloric deficit such as low energy or irritability⁷. Consequently, it is difficult for most people to sustain weight-control behaviours. By contrast, many individuals with anorexia nervosa report finding restrictive eating and excessive exercising at least somewhat appetitive or relieving rather than wholly aversive^8–10 and engage in weight-control behaviours rigidly and repetitively. Individuals with anorexia nervosa engage in weight-control behaviours even after intensive treatment¹¹ and despite acknowledging the potential for negative outcomes, including death¹². Consequently, anorexia nervosa carries elevated physical and psychological morbidity and has one of the highest mortality rates of any psychiatric disorder^13–15.

Some eating disorder behaviours, such as binge eating, are linked to the heightened pursuit of primary reinforcers from experiences that are innately rewarding owing to their link to survival (such as consuming food)^5,16. Eating is naturally pleasurable; therefore, it is easily comprehensible how some individuals would engage in this behaviour to excess. However, there is limited understanding of the forces that maintain eating disorder behaviours that are not as naturally pleasurable, such as restrictive eating¹⁷. When behaviours that are not associated with natural rewards persist over time, this persistence must result from some learning process that teaches the individual that the behaviour serves some valuable function. The most common explanation for why eating disorder behaviours that are not naturally pleasurable (such as restrictive eating) persist is that the outcome of the behaviour has been rewarded by a primary reinforcer. For example, at least in early development of anorexia nervosa¹⁸, the weight loss that results from restrictive eating might be followed by social praise (a primary reinforcer for humans) and therefore restrictive eating persists in an effort to continue receiving social praise linked with weight loss. However, some individuals with anorexia nervosa report minimal or conflicting desire for weight loss¹⁹. Other explanations suggest that alternative factors maintain non-hedonic eating disorder behaviours, such as desire for control, perfectionism or affect regulation^20–22. Because anorexia nervosa is a complex, multifaceted psychiatric illness, each of these proposed factors likely contributes to the weight-control behaviour of individuals with this disorder. However, despite theoretical advancements, treatment outcomes remain poor, especially for adults with anorexia nervosa²³, suggesting an incomplete understanding of the variables that maintain weight-control behaviours in this population. In addition, despite the high psychiatric comorbidity associated with anorexia nervosa¹³, treatments often do not affect other psychopathology²⁴. Thus, more research is needed to understand the factors that maintain anorexia nervosa and other problematic non-hedonic behaviours — such as overemphasis on academic achievement or excess abstemiousness — common to individuals with this eating disorder²⁵.

In this Perspective, we propose that a social psychology theory, learned industriousness²⁶, can account for some of the maintenance of anorexia nervosa and other psychiatric disorders characterized by continued engagement in taxing and not clearly pleasurable behaviours. Although the learned industriousness model was developed 20 years ago, it has not yet been applied to accounts of psychiatric disorders. First, we present the conceptual and empirical underpinnings of learned industriousness and evidence to support this model in non-clinical populations. Second, we review evidence for how learned industriousness might account for the excess engagement in effortful actions that characterizes anorexia nervosa and other psychiatric disorders (such as autism spectrum disorders or obsessive–compulsive spectrum disorders). Last, we suggest a research programme to test the applicability of this model to the understanding of certain persistent psychopathology.

The learned industrious model

Effort is the intensification of physical or mental activity in the service of meeting a goal²⁷. Physical forms of effort (such as exercise, repetitive motor actions) and cognitive forms of effort (such as solving challenging mental problems) are usually considered inherently aversive and are frequently avoided by humans and other animals²⁸. As such, effort is typically modelled in behavioural economics as costly². In addition, there is clear evidence that rewarding outcomes are usually devalued as the effort necessary to obtain them increases²⁹. However, effort can paradoxically be valued and even enjoyable under certain conditions, although to different degrees for different people²⁷. Learned industriousness describes a process that can partially explain this paradox.

The learned industriousness model is built upon a classical conditioning reward framework³⁰. This framework can explain how humans and non-human animals learn to value a cue or a behaviour that is not associated with a primary reinforcing outcome through repeated pairing with a primary reinforcer. The iconic example of classical conditioning comes from experiments that demonstrated that an initially non-rewarding cue (ringing bell) can start to elicit reward responses (salivating) from dogs when repeatedly paired with a primary reinforcer (food presented at the same time as the bell’s sound)³⁰. In this example, the sound of the bell would have become a secondary reinforcer, or a previously unremarkable stimulus that becomes conditioned as rewarding in its own right even in the absence of the primary reinforcer (food). Learned industriousness posits that high-effort behaviour can similarly be conditioned as a secondary reinforcer. In other words, high effort can become rewarding in and of itself when routinely paired with a primary reward such as achieving a desired goal or receiving social praise²⁶.

The learned industriousness model posits that the physical or cognitive experiences of effort begin as neutral (or mildly aversive) stimuli (Fig. 1). However, if effort is repeatedly paired with a primary reinforcer (for instance, social praise), the physical or cognitive experiences of effort become conditioned as pleasurable stimuli because humans and non-human animals learn that these experiences signal that rewards are imminent, altering the subjective value of effort²⁷. Therefore, humans and non-human animals begin to engage in a range of effortful behaviours to experience the internal, subjective rewards associated with effort, regardless of the external outcomes of the effort²⁶. The specific psychological or subjective experiential changes that accompany learned industriousness in humans are not yet a well-understood part of the model. However, several hypotheses have been offered to explain what aspects of effortful (or industrious) behaviour humans might learn to internalize as rewarding (for instance, self-signalled pride or a sense of mastery)¹.

Fig. 1 |. The learned industriousness model.

Individual or environmental predisposing factors might make certain individuals particularly susceptible to learned industriousness conditioning that enhances the subjective value or willingness and/or ability to engage in effortful behaviour such as heightened pursuit of academic achievement. In addition, other individual factors (such as weight-control overvaluation) might predispose initial engagement in exerting effortful non-hedonic eating disorder behaviour. During initial learning of learned industriousness, effortful behaviour (whether or not it is eating disorder relevant) leads to desired outcomes (weight loss, academic achievement) that yield reward (pride, social praise) increasing the subjective value of effort (by altering the perceived ratio of effort reward to effort cost). Repeated over time, this learned industriousness results in effort generalization, resulting in an expansion of the class of effortful behaviour to include novel challenging behaviours. Furthermore, through this repetition, reward conditioning occurs, through which exerting effort itself acquires rewarding properties (rather than solely obtaining reward via the desired outcomes themselves), further increasing the subjective value of effort. If the effortful behaviours are overused or problematic (such as weight-controlling behaviour), psychiatric disorders (such as anorexia nervosa or obsessive–compulsive spectrum disorders) might result. Furthermore, cue discrimination might make an associative connection between disorder-relevant behaviours and rewarding effortful sensations, further conditioning the disorder-specific effortful behaviour. For individuals with anorexia nervosa, alterations to the dopaminergic reward system induced by starvation states could exacerbate this process.

Behavioural evidence

The learned industriousness model was developed within social and behavioural psychology to explain individual differences in the degree to which individual humans (and non-human animals) are willing to engage in effortful behaviour. This model was originally informed by human and non-human animal behavioural data showing that repeatedly rewarding high-effort behaviours increased an animal’s willingness to perform other demanding tasks, even when high effort was no longer necessary to obtain a reward. In a series of studies, researchers found that rats required to exert high effort for reward (such as repeatedly travelling a runway to receive food) in one training task engaged in more frequent and vigorous effort in a subsequent unrelated transfer task (such as bar pressing for food), more often chose high-effort subsequent activities (such as high levels of bar pressing for more food versus low levels of bar pressing for less food) and were more resistant to extinction of the effortful behaviour compared with rats not required to exert high effort for reward during training^31–35. In addition, these results were unaffected when high effort was not required in the secondary transfer task — for instance, food was delivered after every bar press, regardless of effort — or when the amount and rate of reward delivered during initial training was the same for rats that exerted high effort versus control rats that did not^32,34. Furthermore, these high-effort-conditioned rats also engaged in more frequent and vigorous effort in transfer tasks even when they required tolerance of clearly aversive outcomes such as an electric shock³⁴.

In humans, similar patterns have been found in typically functioning undergraduates^36–38, children³³, crowd-sourced adult Internet samples³⁹ and young individuals with problems related to physical inactivity⁴⁰ or related to learning difficulties³³. Rewarding high-effort expenditure on difficult tasks (such as completing challenging math problems) increased effort expenditure and persistence on subsequent tasks that were not associated with an obvious reward (such as repeatedly pressing a computer button)^36,37,41. Although the learned industriousness model was developed to account for individual differences in the engagement of effortful behaviour rather than to address an explicit clinical target, this model has largely been applied in groups with low industriousness (for instance, those under-functioning academically) to increase engagement in effortful behaviour²⁶. Importantly, we were unable to find applications of the learned industriousness model to groups of humans with high industriousness or in individuals in whom effortful behaviour has become excessive.

Several lines of behavioural research suggest that effort itself can be considered desirable²⁷. For instance, animals in their natural environment choose to work for rewards such as food, even when they can obtain these rewards without exerting effort^33,42. A wealth of behavioural data suggest that outcomes become more rewarding as the effort necessary to achieve the outcome increases^27,43. There is also evidence of trait-level differences in the degree to which individuals are willing to exert effort, as some individuals demonstrate elevated motivation for engaging in challenging activities across contexts⁴⁴.

In sum, training an individual human or non-human animal to engage in high-effort behaviour to obtain a reward makes that individual more willing to voluntarily engage in high-effort behaviour in subsequent unrelated tasks. Further, there is evidence that both humans and non-human animals intrinsically value effort under some circumstances. Although other learning theories can account for the emergence of effortful behaviour, learned industriousness is unique in its ability to explain effort generalization (Box 1). However, there are limitations to this behavioural literature supporting learned industriousness that warrant consideration. Most studies were conducted several decades ago by only a few research groups, involved small sample sizes (≤10 rats^31,34) and failed to control for important potential confounding variables (such as performance independent of effort⁴⁵). Patterns of learned industriousness have been replicated, but effect sizes have been modest³⁹. Further, although the learned industriousness model posits that conditioning reduces subjective aversion and increases subjective reward related to engaging in effortful behaviour, this affective aspect of the model has received minimal investigation. Thus, well-powered independent replications with more rigorous controls and more comprehensive designs are needed to further validate the learned industriousness model⁴⁵.

Box 1. Comparing learned industriousness with other pre-clinical effort engagement theories.

Goal-directed learning and habit learning are two other theories that can also explain effort behaviour. In goal-directed learning — often associated with addictive processes — a human or non-human animal exerts effort because the resulting outcome is so rewarding that it makes the costs of the effort worthwhile. Evidence demonstrates that increasing the value of an outcome (such as a monetary reward) strengthens motivation to exert effort¹³⁷, and humans and non-human animals will exert high levels of effort to obtain especially potent reinforcers (such as drugs of abuse)^138–142. Goal-directed effort escalates over time, as more of the effortful behaviour is required to get the same rewarding effect from initially exerting effort. In habit learning, a behaviour that was originally rewarded gets over-trained to the point that it is automatically executed in certain situations irrespective of anticipated outcomes¹⁴³. Humans and non-human animals over-trained on a behaviour will continue executing this action even once the reward is removed^143–145. The habit model posits that specific effortful psychological symptoms (such as compulsions) persist because they have become cue-driven automatic responses divorced from the actual value of these responses^146,147.

Learned industriousness can be distinguished from these alternative theories. The first difference pertains to what and how an animal learns (see table, column 1); for instance, when a rat is trained to traverse a runway for food. In a learned industriousness paradigm, the rodent is rewarded on a fixed ratio for a specific high number of traversals, thereby learning that high effort is rewarded. In a habit learning paradigm, the rodent is repeatedly intermittently rewarded for running, independently of the specific number of traversals, learning that running rather than effort generally is rewarded. In a goal-directed paradigm, the rodent learns that it has to run to receive a highly salient reward (such as high-fat food), focusing on gaining the valuable outcome with enhanced reward salience rather than the learned behaviour. The second difference pertains to when the rat is returned to the same context in which running is no longer rewarded (see table, column 2). In a goal-directed paradigm, running will extinguish for the rodent because running was only a means for obtaining reward. The habit learning and learned industriousness paradigms make effortful behaviour more resistant to extinction. In habit learning, the rodent will continue running because running will have become a non-conscious habit whereas in the learned industriousness paradigm the rodent will continue running because the effortful exertion of running itself will have become rewarding. However, a difference emerges if these rodents are given access to a new unrewarded effortful behaviour (for instance, bar pressing; see table, column 3): in the habit learning paradigm the rodent will not generalize the effortful behaviour to repeated bar pressing because the rat was only over-trained to run. In the learned industriousness paradigm, the rodent will generalize effortful behaviour and engage in bar pressing to obtain enjoyable effort sensations afforded by the novel context. For humans, learned industriousness explains how learning one effortful behaviour (such as athletics) could motivate a different type of effort (such as pursuing mental challenges), thereby accounting for both effort persistence and effort generalization.

Theoretical model	Training (reward learning)	Testing (same context, no reward)	Generalization (new context, no reward)
Learned Industriousness	High effort is rewarded independently of specific behaviour	Effort	Effort
Habit learning	Specific behaviour is rewarded independently of effort	Effort	No effort
Goal-directed learning	Effort is exerted to obtain a high-value reward	No effort	No effort
No learning	Reward is freely available regardless of behaviour or effort	No effort	No effort

Neurobiological evidence

Examining the neurobiological substrates of effort-based activities holds potential for revealing a biological basis for learned industriousness. In line with conceptualizations of effort being aversive, several brain regions track the potential costs of effort expenditure. Activity in the anterior cingulate and the anterior insula correspond to effort discounting^46,47 and track the costs of the energy demands required from effort⁴⁸. The anterior cingulate and the anterior insula also potentially mediate the aversive subjective experience of effort⁴⁹ and the tendency to avoid high-effort activity⁴⁶. By contrast, several brain regions situated within the reward network actively monitor the potential benefits of effort expenditure and provide signals that promote engagement in effortful actions. The ventral and dorsal striatum (especially the dorsomedial ventral striatum⁵⁰) are activated in anticipation of effort expenditure and their activity predicts a willingness to engage in high-effort-based activities^51,52. This activity in the striatum also recruits regions of the prefrontal cortex — most notably the ventromedial prefrontal cortex (vmPFC) — the activity of which tracks the value of the expected rewards from the effortful task⁴⁶ and the willingness to seek high-effort rewards⁵³. Further, dopamine release in the striatum and the vmPFC mediates both the willingness for and the tolerance of high-effort activity^54,55. In clinical investigations, individuals with psychotic disorders and mood disorders show deficient striatal activity during effort-based decision-making^56,57, which corresponds to the inactivity and the effort discounting in individuals with these types of psychiatric disorder⁵⁵.

Although this neuroimaging literature suggests that reward-seeking and effort are intrinsically related, it does not necessarily demonstrate that effort can be intrinsically rewarding. However, following a decision to engage in high-effort behaviour, activity in the striatum increases in anticipation of the high-effort engagement, which might reflect anticipation of an intrinsic reward from the effort in addition to invigoration of the activity that subsequently needs to be performed (such as button pressing)^52,58. Further, the ventral striatum is activated to a greater extent when receiving and evaluating rewards that require greater effort to achieve^59,60. Consequently, rewards obtained through exerting more effort tend to be preferred to rewards obtained exerting less effort⁶¹. In addition, higher dopamine receptor density in the ventral striatum is associated with greater trait-level motivation for achievement⁶². Together, these findings are consistent with the learned industriousness model, in which dopaminergic activity promoted throughout the reward circuitry could be conditioning the subjective value of effort alongside its role in motivating the exertion of the effortful behaviour (Fig. 1).

These data suggest that learned industriousness during decision-making to engage in effort-based behaviour is reflected by increased neural activation in brain regions associated with predicting rewards from efforts (striatum, vmPFC) and decreased neural activation in regions associated with predicting costs of effort (anterior cingulate, anterior insula) (Fig. 2). These activation patterns might correlate with relevant behavioural metrics such as effort willingness and subjective pleasure or effort discounting and subjective aversion, respectively. Although this would be consistent with a biological basis for learned industriousness, the neural correlates of individual-level differences in effort willingness and subjective pleasure derived from effort have not been systematically tested and warrant further research.

Fig. 2 |. Proposed biobehavioural correlates of learned industriousness.

Brain regions and behavioural correlates that represent structures and behaviours expected to increase (yellow) or decrease (red) in activation, frequency or intensity during effort-based decision-making and the resulting action executions that correlate with learned industriousness. aI, anterior insula; BLA, bilateral amygdala; dACC, dorsal anterior cingulate cortex; DS, dorsal striatum; vmPFC, ventromedial prefrontal cortex; VS, ventral striatum.

Applications to anorexia nervosa

The learned industriousness model has not yet been applied to understand psychiatric disorders characterized by excess effortful behaviour. Indeed, most of the clinical literature on effort-based decision-making has examined individuals with deficient effort motivation^{55,56,63–65}. Using the example of anorexia nervosa, we describe how the learned industriousness model can be applied to understand the opposite end of the effort-based decision-making spectrum, in which heightened effort motivation leads to negative psychological consequences.

We propose that effortful eating disorder behaviours might yield short-term reward in individuals with anorexia nervosa because they fall within a class of effortful behaviours that require persistence or intensity that an individual has been conditioned to find reinforcing²⁶. According to the learned industriousness model (Fig. 1), effortful behaviour of individuals with anorexia nervosa originally might be discriminately rewarded (for instance, through social praise or self-accomplishment) for the outcomes of their eating disorder behaviour (such as weight loss) and/or effortful non-eating disorder behaviour (such as increased school performance). Behaviours leading to such outcomes are frequently socially rewarded in cultures that value individualism, self-control and achievement^66,67.

Individuals with anorexia nervosa might also be genetically or temperamentally predisposed to engage in high-effort behaviour — including eating disorder behaviour (such as restrictive eating)^68,69 — and to respond to external rewards for exerting effort (such as social praise)⁷⁰. As such, individuals with anorexia nervosa would be more likely to engage in effortful behaviours — both eating disorder and non-eating disorder related — and to internalize the external rewards that come from engaging in them. Over time, individuals with anorexia nervosa might increasingly internalize self-reinforcement for exerting effort and seek out novel heightened effort experiences, eating disorder related or otherwise²⁶. Similar to the process of fear generalization⁷¹, individuals with anorexia nervosa may begin to overgeneralize the rewards from effortful behaviour to a greater number of behaviours, including behaviours most individuals would not identify as signalling the potential for effort-based rewards (such as overextending oneself in relationships).

Yet, not every individual with heightened industriousness develops eating disorder symptoms, so additional events are required for learned industriousness to translate into eating disorder-focused effortful behaviour. There must be an impetus that spurs initial engagement in non-hedonic disordered eating, which could be intentional (dieting to obtain valued weight-loss outcomes) or unintentional (an illness that precipitates restriction). Learning that eating disorder behaviours generate rewarding effort sensations could provide the required initial incentive if effort behaviours have already been conditioned to be subjectively rewarding. In this case, eating disorder behaviour first needs to be associated with effort. This association could occur on the basis of shared physical or psychological sensations with other challenging activities or through other individuals tagging eating disorder behaviour as effortful (“I don’t know how you can eat so little!”). Similar processes are likely responsible for conditioning any specific form of industriousness over another (for instance, learning to engage in excessive organizing, but not excessive exercising). However, the starvation state experienced by individuals with anorexia nervosa may exacerbate the conditioning of subjective effort-based rewards because food restriction increases the salience of unrelated rewards (such as from drugs of abuse) through sensitization of dopaminergic neural pathways that drive food consumption⁷². Thus, subjective effort valuation could be further enhanced as a byproduct of this sensitization process as well, ossifying learned industriousness into the eating disorder behaviour.

Although this learned industriousness model shares qualities of other theoretical accounts of anorexia nervosa (Box 2), it more explicitly accounts for problematic effort generalization than these other accounts. Even if eating disorder behaviours of an individual were not initially reinforced, the class of effortful behaviour encompassing other types of industrious behaviour (such as athletic activity not linked to weight loss) could be expanded to include eating disorder behaviours (such as restrictive eating) through cue or class generalization. Generalization is a process of building subjective associations between stimuli that share similar qualities (for instance, liking a person you just met because they look like your best friend). Similarly, the subjectively rewarding sensations from the heightened effort associated with eating disorder behaviours could generalize to other problematic effortful behaviours such as excessive studying, cleaning or organizing. Accordingly, multiple levels of reinforcement could surround weight-control behaviours, making them more difficult to change. For example, exercise could be reinforcing both because it leads to a desired outcome (weight loss) and because it requires the exertion of effort. Thus, even if clinical interventions shift the desire for thinness, weight-control behaviours could persist, driven by the intrinsic reward from the effort exerted to express them.

Box 2. Learned industriousness versus related theories of anorexia nervosa.

Goal-directed and habit learning theories of anorexia nervosa, informed by pre-clinical models (see Box 1), have similarly posited a role of aberrant reward learning in the development of anorexia nervosa. Goal-directed theories of anorexia nervosa suggest that weight-control behaviours in individuals with anorexia nervosa are driven by the heightened salience of the rewards derived from weight loss, such as thinness¹⁴⁸, and that weight-control behaviours must escalate over time for individuals with anorexia nervosa to continue to experience the same level of reward⁸¹. In support of this hypothesis, cues for thinness are often highly rewarding to individuals with anorexia nervosa, and weight-loss behaviours do tend to intensify over time^81,116. However, goal-directed theories only account for the excess drive towards weight loss-compatible behaviours in individuals with anorexia nervosa. Further, it would be expected that effortful behaviours not leading to weight change would ultimately extinguish.

Habit learning theories suggest that weight-control behaviours in individuals with anorexia nervosa are initially driven by rewards from weight loss (such as social praise) but through over-training become automatic cue-driven habitual behaviours performed without conscious consideration of the resulting rewards^17,149. Weight-control behaviours in individuals with anorexia nervosa share qualities of habitual behaviour¹⁵⁰. However, it remains unclear whether individuals with anorexia nervosa have a generalized tendency towards habit formation or if only their eating disorder behaviours become habitual^150–152. Habit learning theory accounts for the persistence of specific practised weight-control behaviours, but not general excessive effort engagement in individuals with anorexia nervosa.

Other prominent theories of anorexia nervosa, such as cognitive-behavioural and cognitive-interpersonal theories, identify cognitive mechanisms (perfectionism or the need for control) that may account for persistent effort across behaviours or contexts^20,21. There is substantial evidence to suggest that cognitive variables are relevant to anorexia nervosa^20,112,153. Cognitive mechanisms may explain engagement in effortful behaviours beyond weight-control behaviour, but these theories also identify the outcome of effortful behaviour (for instance, reaching an elevated personal standard) as being rewarding rather than the process of exerting effort. In addition, such theories may not as easily explain a drive towards exerting effort that is not intended to yield a specific outcome (such as a tendency towards ‘staying busy’).

The learned industriousness model of anorexia nervosa differs from the above theories in several crucial ways. First, rewards derived from effortful eating disorder behaviours come from the physical and psychological experience of effort itself, rather than from any outcome derived from effort (such as thinness or external achievement). Second, effort is subjectively experienced as positive, instead of either as aversive but necessary to achieve an outcome (goal-directed theory, cognitive theories) or as value agnostic(habit theory). Third, effort generalization could occur without ever directly contacting positive outcomes of the new behaviour owing to shared associative qualities of effort exertion. For instance, a person could learn that restrictive eating will be subjectively rewarding without ever receiving direct praise or accomplishment from this eating disorder behaviour owing to restrictive eating sharing effortful qualities with academic achievement, which has been conditioned to be experienced as rewarding. Lastly, the timing and pattern of dopaminergic engagement might differ, with dopamine release corresponding to cues that signal effort, rather than with the outcomes of exerting effort, thereby potentially following a pattern of steady dopaminergic ramping (instead of phasic release)¹⁵⁴. Although learned industriousness might explain novel components of anorexia nervosa, it would not replace other theories, as each likely describes some of the mechanisms that maintain this eating disorder.

This model could also be applied to psychiatric disorders beyond anorexia nervosa. Individuals with other eating disorders also engage in effortful weight-control behaviours; for instance, individuals with bulimia nervosa might engage in even more intense and frequent restrictive eating than individuals with anorexia nervosa⁷³. Some symptoms of autism spectrum disorders (such as repetitive engagement in preferred activities) or obsessive–compulsive spectrum disorders (such as overwork in obsessive–compulsive personality disorder) — require individuals to exert high effort towards obtaining outcomes that are not universally enjoyable⁵. This Perspective focuses primarily on anorexia nervosa as a prototype of problematic learned industriousness. However, the principles outlined could extend to these other clinical populations.

Evidence in anorexia nervosa

Although the learned industriousness model of anorexia nervosa we propose above has not been tested directly, there is significant indirect evidence to support the hypothesis that effort-derived reward maintains eating disorder behaviours in individuals with anorexia nervosa.

Qualitative and self-report data

Considerable qualitative and self-report data suggest that some individuals with anorexia nervosa find the effortful quality of eating disorder symptoms rewarding. Individuals with anorexia nervosa have described that behaviours such as restrictive eating, exercising and purging yield feelings of enjoyment, pride, self-confidence or uniqueness^74–78. In one survey study, ~75% of individuals with anorexia nervosa endorsed engagement in restrictive eating as a way to feel strong, powerful or proud¹⁰. Similarly, in ecological momentary assessment research, pride has been found to significantly increase after restrictive eating for individuals with the restricting subtype of anorexia nervosa⁸. Further, in a qualitative survey, individuals with anorexia nervosa were asked to describe how their values corresponded with their eating disorder behaviours⁷⁹. One common theme was that individuals with anorexia nervosa valued the hard work that maintained their eating disorder symptoms. For instance, one respondent indicated, “When I don’t eat and when I do those things it’s kind of like a buzz, in the sense that all the positive aspects that I think about myself — that I have willpower, I’m strong, I’m independent, I feel attractive, I feel confident”⁷⁹. Thus, eating disorder symptoms could emerge as an extension of this positive emphasis placed on exerting effort.

Notably, most individuals with anorexia nervosa report mixed feelings about their eating disorder, identifying numerous costs of weight-control behaviours alongside the perceived rewards⁸⁰. Symptoms may also escalate over time in a manner experienced as aversively compulsive, rather than as a purposeful way to obtain a desired outcome⁸¹. These self-reports of perceived costs do not negate the possibility that the conditioned rewards from exerting effort might drive weight-loss behaviours. Indeed, in pre-clinical studies, learned industriousness conditioning resulted in effort persistence even when effort was paired with aversive consequences (such as electric shock)³⁴, highlighting the durability of this learned behaviour alongside concurrent adverse outcomes. In addition, the rewards of weight-control behaviours (such as pleasurable sensations during effort) can occur more immediately than the adverse outcomes (health consequences) and, thereby, might drive the effortful eating behaviour to a greater degree because the rewards establish that behaviour before the negative outcomes are encountered.

Temperament

Persistence is a temperamental construct that reflects the tendency to work towards longer-term rewards in the face of momentary aversive or non-rewarding experiences⁸². A recent meta-analysis identified elevated persistence across eating disorder presentations relative to control individuals, with the highest effect sizes (Cohen’s d = 0.52) reported for individuals with the restricting subtype of anorexia nervosa⁶⁸. Behavioural data support these findings, as individuals with anorexia nervosa have been found to persist longer on non-eating disorder laboratory tasks than individuals without an eating disorder⁷⁰. Although other temperamental propensities (such as harm avoidance or reward dependence) have been found to change as an individual recovers from anorexia nervosa, persistence remains stable even in recovery⁶⁸, suggesting that this personality characteristic endures beyond acute illness. These data demonstrate that individuals with anorexia nervosa possess long-standing patterns of behaviour aligned with having a preference for long-term, effort-based rewards.

Delay discounting

The literature on delay discounting in anorexia nervosa provides further indirect evidence of heightened effort valuation in individuals with this eating disorder. Delay discounting refers to the devaluation of a reward owing to delay in its receipt, so that rewards become less valuable when their delivery is less immediate⁸³. Delay discounting assessments typically involve presenting participants with several binary choices between smaller rewards received sooner ($5 today) or larger rewards received later ($20 in a week) to determine the delay no longer worth persisting through to obtain larger rewards. Delay and effort are inherently related, as outcomes that take a long time to achieve often require substantial effort. Therefore, it is unsurprising that there is a modest link between delay and effort discounting⁸⁴, indicating that preferences for delayed and effortful rewards are related. Thus, delay discounting can serve as a proxy behaviour potentially relevant to quantifying learned industriousness.

Most psychiatric disorders are characterized by individuals over-discounting delayed rewards, thereby demonstrating difficulty delaying immediate gratification⁸⁵. Anorexia nervosa is one of the few psychiatric disorders that has been associated with under-discounting of delayed rewards, whereby individuals with this eating disorder show a bias for larger rewards available later versus smaller rewards available earlier⁸⁵. This pattern suggests that individuals with anorexia nervosa might also overvalue effortful rewards for the reasons discussed above. However, because exerting effort and tolerating delay are related but distinct constructs, further research is needed on effort discounting in individuals with anorexia nervosa. In addition, under-discounting of delayed rewards in individuals with anorexia nervosa can resolve with weight restoration^86–88 and can also be less pronounced during adolescence or young adulthood^89,90. Thus, this preference for delayed rewards could represent a state-based marker of starvation or chronic weight restriction, rather than a temperamental inclination. Similar influences should be considered in future research investigating effort discounting in anorexia nervosa.

Effort valuation

Effort valuation, or the willingness to work for a rewarding commodity, is another facet of reward processing relevant to individuals with anorexia nervosa⁹¹. Effort valuation is often assessed with progressive ratio paradigms that require participants to expend motor (button presses) or cognitive (solving puzzles) energy to obtain a reward. As the task progresses, the effort required to obtain a reward substantially increases and the willingness of participants to work for a reward typically decreases. Individuals with restrictive eating pathology consistently exert substantial effort compared with control individuals in progressive ratio paradigms when the reward is earning exercise^92–95, caloric restriction⁹⁶ or non-nutritive artificial sweetener⁹⁷ (all weight-control behaviours). It is unclear whether effort expenditure is heightened in these studies because an eating disorder-related reward is at stake, because the effort exerted to obtain the reward is rewarding, or both. However, initial evidence suggests that general effort valuation might affect both weight-control-related and eating-related behaviours. For instance, elite athletes show higher physical effort valuation⁹⁸, and an exercise intervention for sedentary adults reduced sensitivity to the costs of physical effort⁹⁹, suggesting a relationship between general effort valuation and the effortful behaviour of engaging in physical activity. In addition, general eating pathology has been associated with less mental effort avoidance, suggesting that effort valuation may be shifted in eating disorders to favour the rewards of effort over the costs of effort¹⁰⁰.

Engagement in other effortful activities

Individuals with anorexia nervosa engage in effortful activities outside of eating disorder behaviours, evidence that confirms effort generalization in this population. For instance, there is a robust link between competitive, elite athleticism and anorexia nervosa^101,102, that has often been attributed to the appearance, weight or leanness of athletes in certain sports (such as gymnastics or long-distance running). However, elite athletes competing at the national or international level or professionally demonstrate higher eating pathology than athletes competing at lower levels of competition, even in sports that have less pronounced weight focus (such as swimming or volleyball)¹⁰². This suggests a shared mechanism between the high-effort exertion required in elite athleticism and that required to sustain eating disorder behaviour. Indeed, one analysis has argued that the qualities that coaches describe as essential to athletic achievement, such as willingness to engage in difficult tasks, are the same qualities that maintain anorexia nervosa¹⁰³. Persistence and ‘obsessive passion’ among competitive athletes have also been found to predict exercise addiction and injury risk^104,105. Thus, excess drive towards engaging in the effort of athletic activities can be linked to negative outcomes and may constitute an uninvestigated shared mechanism that links elite athleticism and anorexia nervosa.

Additionally, the association between high academic achievement and anorexia nervosa has been well established. There are genetic and familial links between higher educational attainment and anorexia nervosa^69,106,107. Higher school performance is a risk factor for individuals developing anorexia nervosa¹⁰⁸, and individuals with anorexia nervosa have been found to have high academic standards and performance^109,110. Although these associations between anorexia nervosa and high academic achievement have often been attributed to perfectionist tendencies, it is possible that they could result from conditioned reinforcement of industrious or effortful activities.

Summary of evidence

These lines of enquiry suggest that individuals with anorexia nervosa can have a propensity towards greater effort tolerance, effort valuation and effort generalization. These qualities could lead individuals with this eating disorder to more readily engage in a range of effortful behaviours, including academic and athletic endeavours in addition to eating disorder behaviours. The emotional experiences that individuals with anorexia nervosa associate with effort are not as well studied, but qualitative data suggest that the effortful quality of their eating disorder behaviour is found to be at least partially gratifying, increasing their pride and self-assurance.

We propose that this research supports the learned industrious model of anorexia nervosa because it suggests that weight-control behaviours fall within a class of effortful activities that have been conditioned to be associated with reward. However, there are other potential explanations for why individuals with anorexia nervosa may value effort more highly than other individuals. There may be shared qualities of effortful behaviour other than exerting the effort itself that individuals with anorexia nervosa find compelling. For instance, effortful actions are often painful or uncomfortable, and individuals with anorexia nervosa have a greater willingness to tolerate pain¹¹¹ as well as a higher tendency towards self-punishment¹⁰. Individuals with anorexia nervosa also report elevated levels of perfectionism¹¹², and many repetitive effortful behaviours demand a high level of exactitude. Thus, these individuals could seek out industrious actions for other reasons (such as to self-punish, to achieve perfectionist self-satisfaction or to manage cognitive dissonance related to engaging in harmful behaviours), rather than because the effortful behaviour is rewarding. Additional research to directly test the learned industriousness model and compare it against other plausible explanatory models is needed to determine whether learned industriousness fulfils this role in anorexia nervosa.

Clinical implications

Effortful behaviour is generally considered to be aversive, so there are no treatments specifically designed to reduce this class of behaviours. It is far more common for prevention and intervention efforts to attempt to increase effortful engagement¹¹³. However, clinical approaches to altering other problematic but rewarding behaviours (for instance non-suicidal self-injury or substance use) might provide insight into potential interventions for reducing excessively effortful behaviour. Below, we consider how focusing on heightened industriousness as a treatment target could affect therapeutic approaches for anorexia nervosa (and perhaps other psychiatric disorders). Many of the techniques described are already employed in psychological and psychiatric treatments, but reducing effortful behaviour is not explicitly the treatment target for any mental health concern. These existing approaches could be adapted to target effortful behaviours specifically, but, notably, we present only initial ideas about how to begin this process (Fig. 3). Previous behavioural treatments for individuals with anorexia nervosa have demonstrated limited efficacy¹¹⁴, so testing these interventions and developing new intervention approaches will be a crucial future research direction.

Fig. 3 |. Summary of potential therapeutic approaches.

Existing approaches to psychological treatments could be adapted to target excessive engagement in harmful effortful behaviours. a, Approaches that extinguish, reduce or alter reward relations with effort. The goal of these interventions is for individuals to reduce overvaluation of effort rewards by attending to the aversive qualities of effort, removing rewards for effort or building novel functional relations to effort (but that could reduce or eliminate healthy forms of effort). For instance, mindfully attending to the aversive qualities of strenuous exercise. b, Reinforcing functional alternatives to effort is another approach. In this case, the aim is to reinforce alternative effortful or non-effortful activities with less potential for harm (but that could condition new problematic forms of effort). Promoting a volunteer activity as an alternative way to derive accomplishment is an example of such an intervention. c, Approaches that enhance effective effort discrimination. Here, the goal of the intervention is to strengthen discrimination of contexts in which effort is appropriate versus excessive(but discrimination could initially be difficult for the individual to master). For example, having individuals identify bodily cues that signal that more physical activity is safe versus unsafe or excessive. d, Diversifying reward classes is an approach with the aim of reinforcing a broader class of behaviours, including those inconsistent with effort (but could fail to reduce reward derived from effort). For instance, reinforcing low-effort activity such as relaxing outdoors through praise. Instances of activities with increased reward/reinforcement (yellow) and decreased reward/increased mindfulness of aversive qualities (red) are highlighted.

Extinguishing, reducing or altering reward relationswith effort

If excess effort characterizes a broad class of problematic behaviours for an individual (the tendency to push oneself too hard), taking steps to reduce the secondary rewarding qualities of effort might lead to clinical improvement (Fig. 3a). This approach would involve minimizing or ignoring the positive qualities of effort and highlighting the aversive qualities of effort or conditioning new experiences with effortful cues and behaviours. Over time, new learning would occur in which the individual learns to associate effort with greater costs and less secondary reward. Crucially, it is unlikely that all forms of heightened industriousness are problematic, as effortful behaviour is often necessary to achieve valued life goals. Therefore, interventions that reduce the secondary rewarding qualities of effort would need to be implemented with the goal of developing a more balanced calculation of the costs and rewards derived from exerting effort, rather than discouraging all effort outright.

Given the problematic use of aversive therapies in eating disorder treatment¹¹⁵ and the heightened sensitivity to punishment of individuals with anorexia nervosa¹¹⁶, interventions that involve the direct punishment of industriousness are discouraged. However, interventions that involve mindful observation by individuals with anorexia nervosa to attend to the inherently displeasing qualities of demanding cognitive and physical tasks — to shift towards a more balanced calculation of the cost–reward ratio of effort — are encouraged. Another approach could involve having individuals with anorexia nervosa maximize expectancy violations by noticing opportunities where high-effort activity does not yield the expected rewards¹¹⁷. It might also be helpful to minimize exposure to environments or individuals (such as certain gyms or certain coaches) that encourage and reward engagement in excessively effortful behaviour. Such stimulus control interventions are routinely used to minimize exposure to cues for other problematic behaviours (for instance, drug use) and are encouraged for reducing excessive engagement in working (such as identifying a job that does not promote overworking)^118,119. Conversely, deliberate exposure exercises could be used by individuals with anorexia nervosa to tolerate the discomfort of resisting effortful behaviours in situations that prompt excess effort.

Given prior research that indicates the resistance of learned industriousness to extinction^31–35, interventions that condition novel relations between effortful behaviours and their outcomes might be more fruitful. For instance, interventions for burnout often encourage attention to aspects of the work environment that are not associated with exerting effort, such as relationships with colleagues¹¹⁸, instead of trying to fully extinguish the rewards from excessively working. Similarly, individuals with anorexia nervosa could be taught to engage in challenging activities (such as exercise) in ways that emphasize rewards other than overexertion (for instance, pleasurable sensations of moderated movement or social aspects of group exercise)¹²⁰.

Reinforcing functional alternatives to effort

In a somewhat contradictory approach, potential interventions could focus on leveraging the reward derived from the effort to engage in alternative but functionally equivalent activities that are more adaptive than eating disorder behaviours (Fig. 3b). An initial harm reduction step could be for individuals with anorexia nervosa to learn to purposefully select other demanding activities that fall more in line with their long-term goals and that cause less harm than their eating disorder behaviours¹²¹. Similar replacement approaches have effectively reduced other problematic behaviours such as replacing self-harming behaviour with engagement in vigorous physical exercise¹²². For individuals with anorexia nervosa, the focus would be on pursuing safer activities that require similar physical or mental exertion (such as a career or home improvement goal) to that previously exerted to maintain their eating disorder behaviours. However, this proposed intervention could result in individuals with anorexia nervosa seeking reward from new forms of excessively effortful behaviour that yield similarly negative outcomes (such as study ‘addiction’). Therefore, this strategy might only be temporarily helpful to implement, with caution, for individuals with anorexia nervosa who are willing to channel their excessively effortful behaviour towards less-destructive activities but are not ready to relinquish it completely.

Alternatively, the rewarding function of effort could be replaced without requiring the individual with anorexia nervosa to engage in effortful behaviour. If the subjective reward gained from effort is a sense of purpose or pride, individuals with anorexia nervosa can be taught to identify experiences that do not require effort but generate the same affective outcomes (for instance, spiritual activities). Further, such interventions could also condition behaviours traditionally considered as inconsistent with exerting effort to be functionally equivalent to effortful exertion. For instance, therapists can reinforce eating and inactivity as behaviours that warranting being rewarded with pride and a sense of accomplishment⁷⁶.

Enhancing effective effort discrimination

Discrimination training is an intervention that could integrate the positive aspects of the two prior suggestions and assist individuals with anorexia nervosa in identifying appropriate situations in which heightened effort is safe and warranted (Fig. 3c). Discrimination training is a key intervention for treating the overgeneralization of negative affect states such as fear, whereby individuals with overgeneralization of fear are taught to identify even subtle contextual differences between feared and safe stimuli, so that cues are appropriately recognized as safe¹²³. A similar concept to discrimination training could be applied in the case of overgeneralization of industriousness. Individuals with anorexia nervosa could be trained to more effectively distinguish situations in which effort is extraneous (routinely working long hours) versus necessary (temporarily working longer hours to meet a deadline) or distinguish situations in which the cost–benefit ratio makes effortful behaviour problematic (cleaning that leads to skipping a social event) versus worthwhile (cleaning to prepare one’s house for a social event).

Diversifying reward classes and properties

Increasing the diversity of potentially rewarding behaviours is another approach to reduce the dependence on effort for obtaining reward that can avoid pitfalls of the previously mentioned strategies. Certain activities that are typically considered rewarding, such as social interaction, are perceived as unrewarding and aversive by individuals with anorexia nervosa¹¹⁶. In addition, individuals with anorexia nervosa tend to derive less reward from hedonic, high-novelty rewards^68,116. It could also be that individuals who have been conditioned to overvalue effort, such as those with anorexia nervosa, may find low-effort recreation (like observing nature or watching a movie) less enjoyable¹²⁴. Thus, individuals with anorexia nervosa might benefit from support in enhancing the salience of rewarding activities that are not explicitly tied to effort to reduce the reliance on effortful behaviour to generate a positive emotional experience (Fig. 3d). Such approaches have successfully been used to treat other problematic rewarding behaviours, such as using drugs of abuse and overworking^118,125. Specific interventions, such as encouraging evening leisure activities and vacations, have also been used to mitigate the potential for excessive working in vulnerable individuals^118,119. Similarly, individuals with anorexia nervosa could be encouraged to institute ‘effort breaks’ during which they temporarily avoid all forms of heightened effort.

Conclusion

Indirect evidence suggests that the learned industriousness model could explain why individuals with anorexia nervosa tend to over-pursue effortful behaviours. However, this model has not been directly tested in this clinical disorder. Effortful goal pursuit is often considered positive and is encouraged in popular culture and clinical interventions¹¹³. Although there is clinical interest in persistence and effortful behaviour — or the lack thereof — psychiatric examination of effort expenditure is nascent, and research is sparse. A clear research agenda is needed to test the relevance of this model for anorexia nervosa and for other psychiatric disorders that involve the overexertion of effort.

Independent, pre-registered replication of the learned industriousness model in both non-clinical and clinical populations is needed⁴⁵. To investigate the relevance of the learned industriousness model in individuals with anorexia nervosa specifically, more data are needed about effort-based decision-making in this population. Few studies have examined effort-based decision-making in individuals with eating disorders and none has focused on individuals with anorexia nervosa specifically^100,126. Several behavioural paradigms can examine the willingness to expend different amounts of effort to obtain rewards of different magnitudes^46,127–129. These paradigms could be used to confirm whether individuals with anorexia nervosa have a tendency to overvalue effort. However, as the design of those paradigms mainly rests upon the assumption that exerting effort decreases reward motivation, they might need to be adapted to test the learned industriousness model specifically. In addition, emerging computational models offer a way to probe during effort-based decision-making whether less dependence on the magnitude of the external reward is coupled with greater effort selection, as can be expected in the case of learned industriousness^27,130. Incorporating self-reports of subjective affective or cognitive experiences could be beneficial towards understanding effortful behaviour in individuals with anorexia nervosa. Beyond information from qualitative reports, little is known about whether individuals with anorexia nervosa find effort expenditure rewarding, relieving, less aversive but still unpleasant or aversive (but necessary to achieve weight-control goals), which represents a clear gap in knowledge when applying the learned industriousness model to anorexia nervosa.

To our knowledge, no studies have examined the neurobiology of effort overvaluation or potential differences in neural activation to effort in individuals with anorexia nervosa or other psychiatric disorders characterized by excess effort. Clearer establishment of the neural substrates of effort valuation (including effort overvaluation) in individuals with psychiatric disorders and control groups is needed. For instance, dissociable profiles of effort valuation, effort discounting and actual physical effort expenditure have been identified within the ventral striatum in healthy samples⁵⁰. Therefore, more information is needed to understand the precise patterns of neural responding that would be expected in individuals conditioned under learned industriousness. Further research is needed to characterize whether behavioural and neurobiological anomalies in effort responding exist across psychiatric conditions.

Even if initial evidence supports learned industriousness in individuals with anorexia nervosa, unanswered questions regarding the aetiological pathways that underpin this behaviour will remain. Our proposed mechanistic pathway for how learned industriousness manifests in individuals with anorexia nervosa (Fig. 1) is theoretical, so further empirical investigation is needed. For instance, the relative degree to which individual factors (such as genetics, dopaminergic functioning and temperament), environmental factors (such as exposure to messaging that promotes industriousness) or their interactions impact the development of excessive industriousness is unclear. In addition, persistence is often linked to positive outcomes, so most population-level interventions focus on enhancing engagement in effortful activities¹¹³. Thus, it would be vital to know whether such treatment approaches can be iatrogenic for certain individuals and whether alternative approaches that prevent the potential for effortful behaviour being taken to excess might be needed.

Understanding how contextual variables and individual differences affect effort valuation in individuals with anorexia nervosa will also be crucial. For instance, it would be important to understand whether effort expenditure is elevated in individuals with anorexia nervosa only in disease-specific contexts or more generally. Further, distinct decision-making processes might promote disordered eating for different individuals or the same individuals during different stages of illness^131,132 or as a function of starvation, chronicity or other individual or situational variables. It is clear that the willingness to exert effort exists on a continuum in healthy populations²⁷, and the same is likely to be true among individuals with psychiatric disorders. Indeed, one study identified different effort subtypes among individuals with schizophrenia using computational modelling approaches¹³³. These subtypes were associated with distinct symptom profiles, suggesting their clinical utility. Therefore, future research should examine whether aspects of the learned industriousness model characterize all individuals, or just a subset with anorexia nervosa, as individual and contextual differences could predict differential effectiveness of potential interventions.

Finally, the learned industriousness model should be tested in other clinical populations beyond anorexia nervosa that show heightened tendencies towards exerting effort. Research has found elevated persistence in individuals with bulimia nervosa and individuals with other eating disorders^68,124. Individuals with eating disorder symptoms (not anorexia nervosa specifically) and individuals with obsessive–compulsive symptoms exhibit less mental effort avoidance¹⁰⁰, and effort expenditure is elevated among individuals with autism spectrum disorders¹³⁰. Further, individuals with bulimia nervosa, individuals with obsessive–compulsive personality disorder and subsets of individuals with chronic depressive disorders demonstrate shallow delay discounting levels similar to those of individuals with anorexia nervosa, suggesting the potential relevance of effort under-discounting in these populations^134,135. Therefore, research is needed to determine whether overvaluation of effort represents a transdiagnostic psychiatric phenotype. Evidence that some psychiatric disorders might be maintained by effort overvaluation could be paradigm-shifting, indicating that ostensibly positive behaviours can go too far and yield severely adverse outcomes¹³⁶. Further tests of the learned industriousness model could help the field understand a subset of puzzling psychiatric phenomena involving excessive drive towards non-hedonic outcomes that are unexplained and insufficiently treated.