Erik Bijleveld

The Unconscious Eye Opener: Pupil Dilation Reveals Strategic Recruitment of Resources Upon Presentation of Subliminal Reward Cues

Recent research suggests that reward cues, in the absence of awareness, can enhance people’s investment of physical resources (Aarts, Custers, & Marien, 2008; Pessiglione et al., 2007). Pessiglione et al., for example, showed that participants spent more physical effort in a demanding force task when they could gain a high-value coin (a pound) than when they could gain a low-value coin (a penny), even when the coins were presented subliminally (i.e., below the threshold of awareness). One explanation for this intriguing finding is that subliminal reward information is processed strategically—that the costs (i.e., the required effort) and benefits (i.e., the value of the reward) of an action are weighed against each other. However, such a weighing process would require higher control functions (Cohen, Heller, & Ranganath, 2005) that are typically thought to operate only on information available to consciousness (Baars, 2002). Another explanation is that the prime directly boosts resources. From this perspective, the effects of subliminal rewards can be explained in terms of low-level, reflex-like responses to primes (Bargh, 2006). Here, we challenge the latter perspective by examining the interaction of reward value and task demands. We aim to show that resources are not directly recruited in reaction to high-reward cues, but instead are recruited strategically—only when the task requires it, and regardless of whether or not the cues enter conscious awareness. In a computerized experiment, we employed an on-line, physiological index: pupil dilation. Because the pupil dilates with sympathetic activity and constricts with parasympathetic activity (Steinhauer, Siegle, Condray, & Pless, 2004), pupil size is an accurate and unobtrusive measure of the resources invested in a task. Ruling out potential alternative explanations, such as anxiety, research demonstrates that pupil dilation increases when tasks require more resources, either because of variations within or between tasks (Kahneman, 1973) or because of individual differences in, for example, cognitive ability (Ahern & Beatty, 1979). These findings demonstrate that the amount of resources individuals need to mobilize for a task can be reliably indexed by changes in their pupil size. If subliminal reward cues input into the strategic processes involved in resource recruitment, the effects of rewards on pupil dilation should occur when the task is demanding (here, recall of five digits), but not when the task is undemanding (recall of three digits), as undemanding tasks can be completed routinely and do not require many resources. It is important to note that this interactive effect of reward and demand on recruitment of resources is expected to occur regardless of whether the reward is processed consciously or nonconsciously.

Unconscious reward cues increase invested effort, but do not change speed–accuracy tradeoffs

While both conscious and unconscious reward cues enhance effort to work on a task, previous research also suggests that conscious rewards may additionally affect speed-accuracy tradeoffs. Based on this idea, two experiments explored whether reward cues that are presented above (supraliminal) or below (subliminal) the threshold of conscious awareness affect such tradeoffs differently. In a speed-accuracy paradigm, participants had to solve an arithmetic problem to attain a supraliminally or subliminally presented high-value or low-value coin. Subliminal high (vs. low) rewards made participants more eager (i.e., faster, but equally accurate). In contrast, supraliminal high (vs. low) rewards caused participants to become more cautious (i.e., slower, but more accurate). However, the effects of supraliminal rewards mimicked those of subliminal rewards when the tendency to make speed-accuracy tradeoffs was reduced. These findings suggest that reward cues initially boost effort regardless of whether or not people are aware of them, but affect speed-accuracy tradeoffs only when the reward information is accessible to consciousness.

Adaptive Reward Pursuit: How Effort Requirements Affect Unconscious Reward Responses and Conscious Reward Decisions.

When in pursuit of rewards, humans weigh the value of potential rewards against the amount of effort that is required to attain them. Although previous research has generally conceptualized this process as a deliberate calculation, recent work suggests that rudimentary mechanisms-operating without conscious intervention-play an important role as well. In this article, we propose that humans can perform a basic integration of reward value and effort requirements without conscious awareness. Furthermore, we propose that conscious awareness of rewards allows for the use of more advanced functions in reward pursuit, which consider the specific course of action that leads to reward attainment. Using a monetary reward priming paradigm that allows us to dissect the performance effects of rewards (i.e., coins of different value) into conscious and unconscious components, we tested this proposal in 3 experiments. Overall, results indicate that people rely on a simple yet adaptive mechanism that unconsciously conserves effort during reward pursuit, because it makes people more reward sensitive whenever more effort is required of the body. Moreover, consciousness supports a more sophisticated mode of reward pursuit, via which people can strategically conserve effort even further. We discuss these findings in the context of decision making, motivation, and consciousness.

Positive priming and intentional binding: Eye-blink rate predicts reward information effects on the sense of agency

Human society is strongly rooted in peoples experiences of agency; that is, the pervasive feeling that one engages in voluntary behavior and causes ones own actions and resulting outcomes. Rewards and positive affect play an important role in the control of voluntary action. However, the role of positive reward signals in the sense of agency is poorly understood. This study examined effects of reward-related information on the sense of agency by employing the intentional binding paradigm. This paradigm measures the extent to which actions and their effects subjectively shift together across time, reflecting a crucial component of peoples sense of agency. Results showed that intentional binding is stronger when participants are primed with reward-related information via brief exposure to positive pictures. Interestingly, this positive priming effect was moderated by baseline eye-blink rates (an indirect marker of striatal dopaminergic functioning); reward-related information increased intentional binding mainly for participants displaying higher baseline eye-blink rates. These findings suggest a possible role for striatal dopamine activity in the process by which reward-related information shapes the way people see themselves as agents.

Human Reward Pursuit: From Rudimentary to Higher-Level Functions

Human reward pursuit is often found to be governed by conscious assessments of expected value and required effort. Yet research has also indicated that rewards are initially valuated and processed outside of awareness by rudimentary brain structures. Building on both of these findings, we propose a new framework for understanding human performance in the service of reward pursuit. We suggest that people initially process rewards unconsciously, which can boost effort and facilitate performance. Subsequently, people may process rewards more fully, which allows them to make strategic decisions on the basis of task conditions and to consciously reflect on the rewards. Intriguingly, these specific processes associated with full reward processing can cause its effects on performance to diverge from those of initial reward processing. In this article, we review recent research that supports this framework. Finally, we discuss how our framework may lead to a refined yet broadly applicable understanding of the human pursuit of rewards.

Ventral striatum is related to within-subject learning performance.

Learning from feedback involves a network of various cortical and subcortical regions. Although activation in this network has been shown to be especially strong in successful learners, it is currently unclear which of these regions are related to within-subject variation in learning performance. To this aim, 21 subjects performed a probabilistic feedback-learning task consisting of multiple independent Learning blocks and non-learning Control blocks, while functional magnetic resonance imaging data were acquired. In agreement with previous studies, activation in anterior, lateral and medial left prefrontal cortex, insula and superior and inferior parietal cortical regions were found when contrasting Learning and Control blocks. Furthermore, activation in the supplementary motor area, anterior cingulate cortex and bilateral striatum was associated specifically with the learning phase and not the application phase during Learning blocks. Finally, activation only in the ventral striatum was associated with within-subject learning performance across the Learning blocks. Taken together, these latter two results are argued to provide the answer to the main research question: ventral striatum activation is associated with within-subject variations in learning performance. The ventral striatum appears to play a vital role in learning by adjusting behavior based on feedback.

A new perspective on human reward research: How consciously and unconsciously perceived reward information influences performance

The question of how human performance can be improved through rewards is a recurrent topic of interest in psychology and neuroscience. Traditional, cognitive approaches to this topic have focused solely on consciously communicated rewards. Recently, a largely neuroscience-inspired perspective has emerged to examine the potential role of conscious awareness of reward information in effective reward pursuit. The present article reviews research employing a newly developed monetary-reward-priming paradigm that allows for a systematic investigation of this perspective. We analyze this research to identify similarities and differences in how consciously and unconsciously perceived rewards impact three distinct aspects relevant to performance: decision making, task preparation, and task execution. We further discuss whether conscious awareness, in modulating the effects of reward information, plays a role similar to its role in modulating the effects of other affective information. Implications of these insights for understanding the role of consciousness in modulating goal-directed behavior more generally are discussed.

The cortisol response to anticipated intergroup interactions predicts self-reported prejudice.

Objectives While prejudice has often been shown to be rooted in experiences of threat, the biological underpinnings of this threat–prejudice association have received less research attention. The present experiment aims to test whether activations of the hypothalamus-pituitary-adrenal (HPA) axis, due to anticipated interactions with out-group members, predict self-reported prejudice. Moreover, we explore potential moderators of this relationship (i.e., interpersonal similarity; subtle vs. blatant prejudice). Methodology/Principal findings Participants anticipated an interaction with an out-group member who was similar or dissimilar to the self. To index HPA activation, cortisol responses to this event were measured. Then, subtle and blatant prejudices were measured via questionnaires. Findings indicated that only when people anticipated an interaction with an out-group member who was dissimilar to the self, their cortisol response to this event significantly predicted subtle (r = .50) and blatant (r = .53) prejudice. Conclusions These findings indicate that prejudicial attitudes are linked to HPA-axis activity. Furthermore, when intergroup interactions are interpreted to be about individuals (and not so much about groups), experienced threat (or its biological substrate) is less likely to relate to prejudice. This conclusion is discussed in terms of recent insights from social neuroscience.

Effort responses to suboptimal reward cues are related to striatal dopaminergic functioning

Reward cues have been found to increase the investment of effort in tasks even when cues are presented suboptimally (i.e. very briefly), making them hard to consciously detect. Such effort responses to suboptimal reward cues are assumed to rely mainly on the mesolimbic dopamine system, including the ventral striatum. To provide further support for this assumption, we performed two studies investigating whether these effort responses vary with individual differences in markers of striatal dopaminergic functioning. Study 1 investigated the relation between physical effort responses and resting state eye-blink rate. Study 2 examined cognitive effort responses in relation to individually averaged error-related negativity. In both studies effort responses correlated with the markers only for suboptimal, but not for optimal reward cues. These findings provide further support for the idea that effort responses to suboptimal reward cues are mainly linked to the mesolimbic dopamine system, while responses to optimal reward cues also depend on higher-level cortical functions.

Promising High Monetary Rewards for Future Task Performance Increases Intermediate Task Performance

In everyday life contexts and work settings, monetary rewards are often contingent on future performance. Based on research showing that the anticipation of rewards causes improved task performance through enhanced task preparation, the present study tested the hypothesis that the promise of monetary rewards for future performance would not only increase future performance, but also performance on an unrewarded intermediate task. Participants performed an auditory Simon task in which they responded to two consecutive tones. While participants could earn high vs. low monetary rewards for fast responses to every second tone, their responses to the first tone were not rewarded. Moreover, we compared performance under conditions in which reward information could prompt strategic performance adjustments (i.e., when reward information was presented for a relatively long duration) to conditions preventing strategic performance adjustments (i.e., when reward information was presented very briefly). Results showed that high (vs. low) rewards sped up both rewarded and intermediate, unrewarded responses, and the effect was independent of the duration of reward presentation. Moreover, long presentation led to a speed-accuracy trade-off for both rewarded and unrewarded tones, whereas short presentation sped up responses to rewarded and unrewarded tones without this trade-off. These results suggest that high rewards for future performance boost intermediate performance due to enhanced task preparation, and they do so regardless whether people respond to rewards in a strategic or non-strategic manner.