Major depressive disorder (MDD) is characterized by deficient reward functions in the brain. However, existing findings on functional alterations during reward anticipation, reward processing, and learning among MDD patients are inconsistent, and it was unclear whether a common reward system implicated in multiple reward functions is altered in MDD. Here we meta-analyzed 18 past studies that compared brain reward functions between adult MDD patients (N = 477, mean age = 26.50 years, female = 59.40%) and healthy controls (N = 506, mean age = 28.11 years, females = 55.58%), and particularly examined group differences across multiple reward functions. Jack-knife sensitivity and subgroup meta-analyses were conducted to test robustness of findings across patient comorbidity, task paradigm, and reward nature. Meta-regression analyses assessed the moderating effect of patient symptom severity and anhedonia scores. We found during reward anticipation, MDD patients showed lower activities in the lateral prefrontal-thalamus circuitry. During reward processing, patients displayed reduced activities in the right striatum and prefrontal cortex, but increased activities in the left temporal cortex. During reward learning, patients showed reduced activity in the lateral prefrontal–thalamic–striatal circuitry and the right parahippocampal–occipital circuitry but higher activities in bilateral cerebellum and the left visual cortex. MDD patients showed decreased activity in the right thalamus during both reward anticipation and learning, and in the right caudate during both reward processing and learning. Larger functional changes in MDD were observed among patients with more severe symptoms and higher anhedonia levels. The thalamic-striatal circuitry functional alterations could be the key neural mechanism underlying MDD patients overarching reward function deficiencies.

An altered behavioral response to positive reinforcement has been proposed to be a core deficit in attention deficit hyperactivity disorder (ADHD). The spontaneously hypertensive rat (SHR), a congenic animal strain, displays a similarly altered response to reinforcement. The presence of this genetically determined phenotype in a rodent model allows experimental investigation of underlying neural mechanisms. Behaviorally, the SHR displays increased preference for immediate reinforcement, increased sensitivity to individual instances of reinforcement relative to integrated reinforcement history, and a steeper delay of reinforcement gradient compared to other rat strains. The SHR also shows less development of incentive to approach sensory stimuli, or cues, that predict reward after repeated cue-reward pairing. We consider the underlying neural mechanisms for these characteristics. It is well known that midbrain dopamine neurons are initially activated by unexpected reward and gradually transfer their responses to reward-predicting cues. This finding has inspired the dopamine transfer deficit (DTD) hypothesis, which predicts certain behavioral effects that would arise from a deficient transfer of dopamine responses from actual rewards to reward-predicting cues. We argue that the DTD predicts the altered responses to reinforcement seen in the SHR and individuals with ADHD. These altered responses to reinforcement in turn predict core symptoms of ADHD. We also suggest that variations in the degree of dopamine transfer may underlie variations in personality dimensions related to altered reinforcement sensitivity. In doing so, we highlight the value of rodent models to the study of human personality.

The constructs of motivation (or needs, motives, etc.) to explain higher-order behavior have burgeoned in psychology. In this article, we critically evaluate such high-level motivation constructs that many researchers define as causal determinants of behavior. We identify a fundamental issue with this predominant view of motivation, which we called the black-box problem. Specifically, high-level motivation constructs have been considered as causally instigating a wide range of higher-order behavior, but this does not explain what they actually are or how behavioral tendencies are generated. The black box problem inevitably makes the construct ill-defined and jeopardizes its theoretical status. To address the problem, we discuss the importance of mental computational processes underlying motivated behavior. Critically, from this perspective, motivation is not a unitary construct that causes a wide range of higher-order behavior --- it is an emergent property that people construe through the regularities of subjective experiences and behavior. The proposed perspective opens new avenues for future theoretical development, i.e., the examination of how motivated behavior is realized through mental computational processes.

Reward processing dysfunctions are considered a candidate mechanism underlying anhedonia and apathy in depression. Neuroimaging studies have documented that neurofunctional alterations in mesocorticolimbic circuits may neurally mediate these dysfunctions. However, common and distinct neurofunctional alterations during motivational and hedonic evaluation of monetary and natural rewards in depression have not been systematically examined. Here, we capitalized on pre-registered neuroimaging meta-analyses to (1) establish general reward-related neural alterations in depression, (2) determine common and distinct alterations during the receipt and anticipation of monetary v. natural rewards, and, (3) characterize the differences on the behavioral, network, and molecular level. The pre-registered meta-analysis (https://osf.io/ay3r9) included 633 depressed patients and 644 healthy controls and revealed generally decreased subgenual anterior cingulate cortex and striatal reactivity toward rewards in depression. Subsequent comparative analyses indicated that monetary rewards led to decreased hedonic reactivity in the right ventral caudate while natural rewards led to decreased reactivity in the bilateral putamen in depressed individuals. These regions exhibited distinguishable profiles on the behavioral, network, and molecular level. Further analyses demonstrated that the right thalamus and left putamen showed decreased activation during the anticipation of monetary reward. The present results indicate that distinguishable neurofunctional alterations may neurally mediate reward-processing alterations in depression, in particular, with respect to monetary and natural rewards. Given that natural rewards prevail in everyday life, our findings suggest that reward-type specific interventions are warranted and challenge the generalizability of experimental tasks employing monetary incentives to capture reward dysregulations in everyday life.

There is an increasing requirement for tools to assess and improve animal welfare in an objective and scientifically based manner. In our research a concept of welfare is applied which states that welfare is determined by the balance between positive and negative experiences. This concept implies that an interaction exists between stress systems and reward systems in the brain and, as a consequence: (I) negative experiences induce an increased sensitivity (ie need) for positive experiences; and (II) negative experiences can be compensated for by positive experiences. On this basis, two uses of reward-related behaviour can be hypothesised: (I) reward sensitivity may be used as a tool to assess the state of an animal in terms of welfare because it can indicate the current state of the balance that is dependent on previous (stressful) experiences; and (II) regular presentation of rewards may serve as a tool to counteract stress by shifting the balance to the positive side and, thus, to improve welfare. In order to investigate this, we used the rat as a model. Reward sensitivity was determined by the spontaneous behavioural response shown during expectation of a reward (ie anticipatory behaviour). A third (III) use of reward-related behaviour derives from the fact that anticipatory behaviour is influenced by the (rewarding) properties of the forthcoming reward (or other event) and, thus, may serve as a tool to assess the animal's perception of this reward/event. This paper presents a descriptive overview of the evidence obtained thus far for the three proposed uses of reward-related behaviour. The biological background of our concept of welfare can be generalised to all (vertebrate) species, and anticipatory behaviour can be evoked in a wide range of other species. Therefore, this tool for measuring and improving the welfare of captive animals has great potential and will contribute to a good quality of life for captive animals.

Risk and reward are negatively correlated in a wide variety of environments, and in many cases this trade off approximates a fair bet. Pleskac and Hertwig (2014) recently proposed that people have internalized this relationship and use it as the basis for probability estimation and subsequent choice under conditions of uncertainty. Specifically, they showed that risky options with high-value outcomes are inferred to have lower probability than options offering a less valuable reward. We report two experiments that test a simple corollary of this idea. In both studies, participants estimated the magnitude of prizes offered by lotteries with known win-probabilities. The relationship between estimates and probabilities followed the power relationship predicted by the risk-reward heuristic, albeit with a tendency to overestimate outcome magnitude. In addition, people’s estimates predicted their willingness to take the gamble. Our results provide further evidence that people have internalized the ecological relationship between risk and reward in financial lotteries, and we suggest that this relationship exerts a wide-ranging influence on decision-making.

This study has its basis in recent findings by our own and other laboratories and proposes a type of rewarded operant learning that seeks the detection of discriminatory cues as a cognitive enrichment in intensive husbandry systems. This type of cognitive enrichment has the ability to activate the intrinsically-rewarding mesolimbic brain axis when an animal acquires successful strategies to cope with environmental demands. It provides animals with the opportunity to develop positive affects through control of their environment and the anticipation of consummatory reward. If true animal welfare is considered more than simply the absence of stress and harm, provoking better affective conditions may be a suitable way of increasing the well-being of intensively-housed animals. Recent research with elaborated operant learning equipment, under experimental and quasi-commercial conditions, revealed better health, reduced boredom and less maladaptive behaviour as potentially practical advantages. A number of the issues regarding the transfer of this suggested form of cognitive enrichment to large scale, commercial farming are discussed.

Scholars in economics and psychology have created a large literature studying reward, punishment and reciprocity. Labor markets constitute a popular application of this body of work, with particular emphasis on how reciprocity helps regulate workplace relationships where managers are unable to perfectly monitor workers.

We study how idiosyncratic features of the labor market (compared to most scenarios in which reciprocity applies) affect the nature of worker reciprocity. In particular, we show how having an excess supply of workers (simulating unemployment) and managers who can observe the reciprocal behavior of workers and hire/fire them on that basis (simulating the reputational concerns inherent in labor market transactions) profoundly alters worker reciprocity. In the absence of reputational concerns, workers tend to reward kind behavior and punish unkind behavior by managers in approximately equal measure. In the presence of reputational concerns, workers exhibit a marked increase (decrease) in the propensity to reward kind (punish unkind) behavior by managers. We demonstrate how this is a consequence of workers and managers responding to changes in the strategic incentives to reward and punish.