Effort, reward and self-reported mental health: a simulation study on negative affectivity bias.

Background : In the present article, we propose an alternative method for dealing with negative affectivity (NA) biases in research, while investigating the association between a deleterious psychosocial environment at work and poor mental health. First, we investigated how strong NA must be to cause an observed correlation between the independent and dependent variables. Second, we subjectively assessed whether NA can have a large enough impact on a large enough number of subjects to invalidate the observed correlations between dependent and independent variables.Methods : We simulated 10,000 populations of 300 subjects each, using the marginal distribution of workers in an actual population that had answered the Siegrist's questionnaire on effort and reward imbalance (ERI) and the General Health Questionnaire (GHQ).Results : The results of the present study suggested that simulated NA has a minimal effect on the mean scores for effort and reward. However, the correlations between the effort and reward imbalance (ERI) ratio and the GHQ score might be important, even in simulated populations with a limited NA.Conclusions : When investigating the relationship between the ERI ratio and the GHQ score, we suggest the following rules for the interpretation of the results: correlations with an explained variance of 5% and below should be considered with caution; correlations with an explained variance between 5% and 10% may result from NA, although this effect does not seem likely; and correlations with an explained variance of 10% and above are not likely to be the result of NA biases. [Authors]

Electrocortical responses in reward paradigms and their variation related to personality

This thesis was conducted in order to investigate two issues: (1) how sensitive event related potentials (ERPs), and more specifically the medial frontal negativity and the P3 components, are to the valence and magnitude of reward-related stimuli, and (2) whether individual differences have an effect on the sensitivity of these ERP components to these characteristics. This was investigated using two reward-related paradigms. In the "pure gambling task" participants were asked to choose between two cards, each containing varying dollar amounts (large or small). The outcome of the choice (i.e., win or loss) was revealed after the choice was made. Additionally, participants were shown whether the non-chosen card would have been a win or a loss. In the "simple response task", participants were presented with five cues (large win, large loss, small win, small loss or zero) that labelled the trial as either a potential win, a potential loss or no change. Following the cue, a target appeared on the screen and the participant's task was to press the response key while the target was still visible. A success led to a win (gain in money) or no loss (no change) depending on the cue. Thirty participants completed both tasks; afterwards they filled out a set of questionnaires measuring personality and other individual differences relating to risk-taking behaviour. The results of both tasks showed that ERP components can differentiate between the valence and magnitude of reward-related stimuli, although no single component was uniquely related to either of the characteristics as previous suggested in the literature. Additionally, the context of the stimulus presentation (e.g., the task structure, condition within the task) affected the relationships between the ERP components and stimulus characteristics.

Thomas Young reward claim, October 30, 1875

Transcript: Sir I understand that a reward of fifty dollars has been offered by the County of Haldimand for the arrest of any person convicted of horse stealing. I beg to state that I arrested Albert Hucker charged with having stolen a bay mare the property of Eward Hodges in the Township of Walpole Co. of Haldimand and that the said Albert Hucker has been convicted of the offence by A.G. Hill, Esq. police magistrate of the Town of Clifton County of Welland, and sentenced to three years servitude in the provincial penitentiary. I beg therefore to ask of I am entitled to the aforesaid reward and if so what steps are necessary to procure it. I am Sir, Yours respectfully, Thomas H. Young Ontario Police Clifton

Response of plant-pollinator communities to fire: changes in diversity, abundance and floral reward structure

Globally, plant-pollinator communities are subject to a diverse array of perturbations and in many temperate and semi-arid systems fire is a dominant structuring force. We present a novel and highly integrated approach, which quantifies, in parallel, the response to fire of pollinator communities, floral communities and floral reward structure. Mt Carmel, Israel is a recognised bee-flower biodiversity hotspot, and using a chronosequence of habitats with differing post-fire ages, we follow the changes in plant-pollinator community organisation from immediately following a burn until full regeneration of vegetation. Initially, fire has a catastrophic effect on these communities, however, recovery is rapid with a peak in diversity of both flowers and bees in the first 2 years post-fire, followed by a steady decline over the next 50 years. The regeneration of floral communities is closely matched by that of their principal pollinators. At the community level we quantify, per unit area of habitat, key parameters of nectar and pollen forage known to be of importance in structuring pollinator communities. Nectar Volume, nectar water content, nectar concentration and the diversity of nectar foraging niches are all greatest immediately following fire with a steady decrease as regeneration proceeds. Temporal changes in energy availability for nectar, pollen, total energy (nectar + pollen) and relative importance of pollen to nectar energy show a similar general decline with site age, however, the pattern is less clear owing to the highly patchy distribution of floral resources. Changes in floral reward structure reflect the general shift from annuals (generally low-reward open access flowers) to perennials (mostly high-reward and restricted access flowers) as post-fire regeneration ensues. The impact of fire on floral communities and their associated rewards have clear implications for pollinator community structure and we discuss this and the role of other disturbance factors on these systems.

Nocturnal ranging behaviour of urban hedgehogs, Erinaceus europaeus, in relation to risk and reward

Urban areas have both positive and negative influences on wildlife. For terrestrial mammals, one of the principle problems is the risk associated with moving through the environment whilst foraging. In this study, we examined nocturnal patterns of movement of urban-dwelling hedgehogs (Erinaceus europaeus) in relation to (i) the risks posed by predators and motor vehicles and (ii) nightly weather patterns. Hedgehogs preferentially utilised the gardens of semi-detached and terraced houses. However, females, but not males, avoided the larger back gardens of detached houses, which contain more of the habitat features selected by badgers. This difference in the avoidance of predation risk is probably associated with sex differences in breeding behaviour. Differences in nightly movement patterns were consistent with strategies associated with mating behaviour and the accumulation of fat reserves for hibernation. Hedgehogs also exhibited differences in behaviour associated with the risks posed by humans; they avoided actively foraging near roads and road verges, but did not avoid crossing roads per se. They were, however, significantly more active after midnight when there was a marked reduction in vehicle and foot traffic. In particular, responses to increased temperature, which is associated with increased abundance of invertebrate prey, were only observed after midnight. This variation in the timing of bouts of activity would reduce the risks associated with human activities. There were also profound differences in both area ranged and activity with chronological year which warrant further investigation.

How reward modulates mimicry: EMG evidence of greater automatic facial mimicry of more rewarding faces

Spontaneous mimicry is a marker of empathy. Conditions characterized by reduced spontaneous mimicry (e.g., autism) also display deficits in sensitivity to social rewards. We tested if spontaneous mimicry of socially rewarding stimuli (happy faces) depends on the reward value of stimuli in 32 typical participants. An evaluative conditioning paradigm was used to associate different reward values with neutral target faces. Subsequently, electromyographic activity over the Zygomaticus Major was measured whilst participants watched video clips of the faces making happy expressions. Higher Zygomaticus Major activity was found in response to happy faces conditioned with high reward versus low reward. Moreover, autistic traits in the general population modulated the extent of spontaneous mimicry of happy faces. This suggests a link between reward and spontaneous mimicry and provides a possible underlying mechanism for the reduced response to social rewards seen in autism.

Fetal programming effects of testosterone on the reward system and behavioral approach tendencies in humans

BACKGROUND: Sex differences are present in many neuropsychiatric conditions that affect emotion and approach-avoidance behavior. One potential mechanism underlying such observations is testosterone in early development. Although much is known about the effects of testosterone in adolescence and adulthood, little is known in humans about how testosterone in fetal development influences later neural sensitivity to valenced facial cues and approach-avoidance behavioral tendencies. METHODS: With functional magnetic resonance imaging we scanned 25 8-11-year-old children while viewing happy, fear, neutral, or scrambled faces. Fetal testosterone (FT) was measured via amniotic fluid sampled between 13 and 20 weeks gestation. Behavioral approach-avoidance tendencies were measured via parental report on the Sensitivity to Punishment and Sensitivity to Rewards questionnaire. RESULTS: Increasing FT predicted enhanced selectivity for positive compared with negatively valenced facial cues in reward-related regions such as caudate, putamen, and nucleus accumbens but not the amygdala. Statistical mediation analyses showed that increasing FT predicts increased behavioral approach tendencies by biasing caudate, putamen, and nucleus accumbens but not amygdala to be more responsive to positive compared with negatively valenced cues. In contrast, FT was not predictive of behavioral avoidance tendencies, either through direct or neurally mediated paths. CONCLUSIONS: This work suggests that testosterone in humans acts as a fetal programming mechanism on the reward system and influences behavioral approach tendencies later in life. As a mechanism influencing atypical development, FT might be important across a range of neuropsychiatric conditions that asymmetrically affect the sexes, the reward system, emotion processing, and approach behavior.

Neural processing of reward and punishment in young people at increased familial risk of depression

Background Abnormalities in the neural representation of rewarding and aversive stimuli have been well-described in patients with acute depression, and we previously found abnormal neural responses to rewarding and aversive sight and taste stimuli in recovered depressed patients. The aim of the present study was to determine whether similar abnormalities might be present in young people at increased familial risk of depression but with no personal history of mood disorder. Methods We therefore used functional magnetic resonance imaging to examine the neural responses to pleasant and aversive sights and tastes in 25 young people (16–21 years of age) with a biological parent with depression and 25 age- and gender-matched control subjects. Results We found that, relative to the control subjects, participants with a parental history of depression showed diminished responses in the orbitofrontal cortex to rewarding stimuli, whereas activations to aversive stimuli were increased in the lateral orbitofrontal cortex and insula. In anterior cingulate cortex the at-risk group showed blunted neural responses to both rewarding and aversive stimuli. Conclusions Our findings suggest that young people at increased familial risk of depression have altered neural representation of reward and punishment, particularly in cortical regions linked to the use of positive and negative feedback to guide adaptive behavior.

Sex differences in reward-related decision processing under stress

Recent research indicates gender differences in the impact of stress on decision behavior, but little is known about the brain mechanisms involved in these gender-specific stress effects. The current study used functional magnetic resonance imaging (fMRI) to determine whether induced stress resulted in gender-specific patterns of brain activation during a decision task involving monetary reward. Specifically, we manipulated physiological stress levels using a cold pressor task, prior to a risky decision making task. Healthy men (n = 24, 12 stressed) and women (n = 23, 11 stressed) completed the decision task after either cold pressor stress or a control task during the period of cortisol response to the cold pressor. Gender differences in behavior were present in stressed participants but not controls, such that stress led to greater reward collection and faster decision speed in males but less reward collection and slower decision speed in females. A gender-by-stress interaction was observed for the dorsal striatum and anterior insula. With cold stress, activation in these regions was increased in males but decreased in females. The findings of this study indicate that the impact of stress on reward-related decision processing differs depending on gender.

Neural basis of the undermining effect of monetary reward on intrinsic motivation

Contrary to the widespread belief that people are positively motivated by reward incentives, some studies have shown that performance-based extrinsic reward can actually undermine a person's intrinsic motivation to engage in a task. This “undermining effect” has timely practical implications, given the burgeoning of performance-based incentive systems in contemporary society. It also presents a theoretical challenge for economic and reinforcement learning theories, which tend to assume that monetary incentives monotonically increase motivation. Despite the practical and theoretical importance of this provocative phenomenon, however, little is known about its neural basis. Herein we induced the behavioral undermining effect using a newly developed task, and we tracked its neural correlates using functional MRI. Our results show that performance-based monetary reward indeed undermines intrinsic motivation, as assessed by the number of voluntary engagements in the task. We found that activity in the anterior striatum and the prefrontal areas decreased along with this behavioral undermining effect. These findings suggest that the corticobasal ganglia valuation system underlies the undermining effect through the integration of extrinsic reward value and intrinsic task value.

Consolidation power of extrinsic rewards: reward cues enhance long-term memory for irrelevant past events

Recent research suggests that extrinsic rewards promote memory consolidation through dopaminergic modulation processes. However, no conclusive behavioral evidence exists given that the influence of extrinsic reward on attention and motivation during encoding and consolidation processes are inherently confounded. The present study provides behavioral evidence that extrinsic rewards (i.e., monetary incentives) enhance human memory consolidation independently of attention and motivation. Participants saw neutral pictures, followed by a reward or control cue in an unrelated context. Our results (and a direct replication study) demonstrated that the reward cue predicted a retrograde enhancement of memory for the preceding neutral pictures. This retrograde effect was observed only after a delay, not immediately upon testing. An additional experiment showed that emotional arousal or unconscious resource mobilization cannot explain the retrograde enhancement effect. These results provide support for the notion that the dopaminergic memory consolidation effect can result from extrinsic reward. (PsycINFO Database Record (c) 2013 APA, all rights reserved)(journal abstract)