Amitai Shenhav | Princeton University (original) (raw)

Papers by Amitai Shenhav

Previous theories predict that human dorsal anterior cingulate (dACC) should respond to decision ... more Previous theories predict that human dorsal anterior cingulate (dACC) should respond to decision difficulty. An alternative theory has been recently advanced that proposes that dACC evolved to represent the value of 'non-default', foraging behavior, calling into question its role in choice difficulty. However, this new theory does not take into account that choosing whether or not to pursue foraging-like behavior can also be more difficult than simply resorting to a default. The results of two neuroimaging experiments show that dACC is only associated with foraging value when foraging value is confounded with choice difficulty; when the two are dissociated, dACC engagement is only explained by choice difficulty, and not the value of foraging. In addition to refuting this new theory, our studies help to formalize a fundamental connection between choice difficulty and foraging-like decisions, while also prescribing a solution for a common pitfall in studies of reward-based decision making.

Win-win choices cause anxiety, often moreso than decisions lacking the opportunity for a highly d... more Win-win choices cause anxiety, often moreso than decisions lacking the opportunity for a highly desired outcome. These anxious feelings can paradoxically co-occur with positive feelings raising important implications for individual decision styles and general wellbeing. Across three studies people chose between products that varied in personal value. Participants reported feeling most positive and most anxious when choosing between similarly high-valued products. Behavioral and neural results suggested that this paradoxical experience resulted from parallel evaluations of the expected outcome (inducing positive affect) versus the cost of choosing a response (inducing anxiety). Positive feelings were reduced when there was no high value option, and anxiety was reduced when only one option was highly valued. Dissociable regions within striatum and medial prefrontal cortex (mPFC) tracked these dueling affective reactions during choice. Ventral regions, associated with stimulus valuation, tracked positive feelings and the value of the best item. Dorsal regions, associated with response valuation, tracked anxiety. In addition to tracking anxiety, dorsal mPFC was associated with conflict during the current choice, and activity levels across individual items predicted whether that choice would later be reversed during an unexpected reevaluation phase. By revealing how win-win decisions elicit responses in dissociable brain systems these results help resolve the paradox of win-win choices. They also provide insight into behaviors that are associated with these two forms of affect, such as why we are pulled toward good options but may still decide to delay or avoid choosing among them.

A decade’s research highlights a critical dissociation between automatic and controlled influence... more A decade’s research highlights a critical dissociation between automatic and controlled influences on moral judgment, subserved by distinct neural structures. Specifically, negative automatic emotional responses to prototypically harmful actions (e.g. pushing someone off of a footbridge) compete with controlled responses favoring the best consequences (e.g. saving five lives instead of one). It is unknown how such competitions are resolved to yield “all things considered” judgments. Here we examine such integrative moral judgments. Drawing on insights from research on self-interested, value-based decision-making in humans and animals, we test a theory concerning the respective contributions of the amygdala and ventromedial prefrontal cortex (vmPFC) to moral judgment. Participants undergoing fMRI responded to moral dilemmas, separately evaluating options for their utility (Which does the most good?), emotional aversiveness (Which feels worse?), and overall moral acceptability. Behavioral data indicate that emotional aversiveness and utility jointly predict “all things considered” integrative judgments. Amygdala response tracks the emotional aversiveness of harmful utilitarian actions as well as overall disapproval of such actions. During such integrative moral judgments, the vmPFC is preferentially engaged, relative to utilitarian and emotional assessments. Amygdala-vmPFC connectivity varies with the role played by emotional input in the task, lowest for pure utilitarian assessments and highest for pure emotional assessments. These findings, which parallel those of research on self-interested economic decision-making, support the hypothesis that the amygdala provides an affective assessment of the action in question, while the vmPFC integrates that signal with a utilitarian assessment of expected outcomes to yield “all things considered” moral judgments.

Disgust reactions can be elicited using stimuli that engender orogastric rejection (e.g., pus and... more Disgust reactions can be elicited using stimuli that engender orogastric rejection (e.g., pus and vomit; Core Disgust stimuli), but also using images of bloody injuries or medical procedures (e.g., surgeries; Blood-[Body] Boundary Violation [B-BV] Disgust stimuli). These two types of disgust reaction are believed to be connected by a common evolutionary function of avoiding either food- or blood-borne contaminants. However, reactions to the category of bloody injuries are typically conflated with reactions to the potential pain being experienced by the victim. This may explain why the two forms of ‘disgust,’ though similarly communicated (through self-report and facial expressions) evince different patterns of physiological reactivity. We therefore tested whether the communicative similarities and physiological dissimilarities would hold when markers of potential contamination in the latter category are removed, leaving only painful injuries that lack blood or explicit body-envelope violations. Participants viewed films that depicted imagery associated with (1) core disgust, (2) painful injuries, or (3) neutral scenes while we measured facial, cardiovascular, and gastric reactivity, respectively. Whereas communicative measures (self-report and facial muscles) suggested that participants experienced increased disgust for both core disgust and painful injuries, peripheral physiology dissociated the two: core disgust decreased normal gastric activity and painful-injury disgust decelerated heart rate and increased heart rate variability. These findings suggest that expressions of disgust toward bodily injuries may reflect a fundamentally different affective response than those evoked by core disgust, and that this (cardiovascularly-mediated) response may in fact be more closely tied to pain-perceptions (or empathy) rather than contaminant-laden stimuli.

The dorsal anterior cingulate cortex (dACC) has a near-ubiquitous presence in the neuroscience of... more The dorsal anterior cingulate cortex (dACC) has a near-ubiquitous presence in the neuroscience of cognitive control. It has been implicated in a diversity of functions, from reward processing and performance monitoring to the execution of control and action selection. Here, we propose that this diversity can be understood in terms of a single underlying function: allocation of control based on an evaluation of the expected value of control (EVC). We present a normative model of EVC that integrates three critical factors: the expected payoff from a controlled process, the amount of control that must be invested to achieve that payoff, and the cost in terms of cognitive effort. We propose that dACC integrates this information, using it to determine whether, where and how much control to allocate. We then consider how the EVC model can explain the diverse array of findings concerning dACC function.

The brain stores information in an associative manner so that contextually related entities are c... more The brain stores information in an associative manner so that contextually related entities are connected in memory. Such associative representations mediate the brain’s ability to generate predictions about other objects and events to expect in a given context. Likewise, the brain encodes and is able to rapidly retrieve the affective value of stimuli in our environment. That both contextual associations and affect serve as building blocks of numerous mental functions often makes interpretation of brain activation ambiguous. A critical brain region where such activation has often resulted in equivocal interpretation is the medial orbitofrontal cortex (mOFC), which has been implicated separately in both affective and associative processing. To characterize its role more unequivocally, we tested whether activity in mOFC was most directly attributable to affective processing, associative processing, or to a combination of both. Participants performed an object recognition task while undergoing fMRI scans. Objects varied independently in their affective valence and in their degree of association with other objects (associativity). Analyses revealed an overlapping sensitivity whereby left mOFC responded both to increasingly positive affective value and to stronger associativity. These two properties individually accounted for mOFC response, even after controlling for their interrelationship. The role of mOFC is either general enough to encompass both associations that link stimuli with reinforcing outcomes and with other stimuli, or abstract enough to use both valence and associativity in conjunction to inform downstream processes related to perception and action. These results may further point to a fundamental relationship between associativity and positive affect.

A new study has used optogenetic methods to stimulate prefrontal-brainstem neuromodulatory pathwa... more A new study has used optogenetic methods to stimulate prefrontal-brainstem neuromodulatory pathways while animals face environmental stressors, the results providing further compelling evidence that prefrontal control of neuromodulatory function can have a dramatic effect on motivated behavior.

Abstract Several studies have demonstrated that mood states influence the number of associations ... more Abstract Several studies have demonstrated that mood states influence the number of associations formed between remotely related concepts. Someone in a neutral or negative mood might draw the association between cold and hot, whereas someone in a positive mood might spontaneously form the more distant association between cold and sneeze. Could the reverse be true, that generating increasingly broad or narrow associations will put someone in a more or less positive mood?

Neuroscientifically specifying the hypotheses of Hume, Marx, Freud, and others on the motivationa... more Neuroscientifically specifying the hypotheses of Hume, Marx, Freud, and others on the motivational sources of religion, the authors present an important case for religiosity as an anti-anxiety device to buffer against feelings of diminished certainty, order, control, and knowledge (stipulated components of meaning). The general evidence for this hypothesis is data showing a reduction in a previously wellcharacterized error-related neuronal response in the anterior cingulate cortex (ACC) among religious persons. The authors' interpretation of these effects as a marker of religion's inherent anxiolytic influence is an intriguing one. In addition to the paper's focus on degrees of general reactivity to perceived threats to certainty, order, control, and knowledge, we feel it would also be very interesting to consider the ways in which this conflict/uncertainty is resolved across individuals. Specifically, we suggest that individuals who rely differentially on fast/automatic/intuitive versus slow/controlled/ reflective reasoning will arrive at different solutions when encountering the same questions of meaning making.

Some have argued that belief in God is intuitive, a natural (by-)product of the human mind given ... more Some have argued that belief in God is intuitive, a natural (by-)product of the human mind given its cognitive structure and social context. If this is true, the extent to which one believes in God may be influenced by one’s more general tendency to rely on intuition versus reflection. Three studies support this hypothesis, linking intuitive cognitive style to belief in God. Study 1 showed that individual differences in cognitive style predict belief in God. Participants completed the Cognitive Reflection Test (CRT; Frederick, 2005), which employs math problems that, although easily solvable, have intuitively compelling incorrect answers. Participants who gave more intuitive answers on the CRT reported stronger belief in God. This effect was not mediated by education level, income, political orientation, or other demographic variables. Study 2 showed that the correlation between CRT scores and belief in God also holds when cognitive ability (IQ) and aspects of personality were controlled. Moreover, both studies demonstrated that intuitive CRT responses predicted the degree to which individuals reported having strengthened their belief in God since childhood, but not their familial religiosity during childhood, suggesting a causal relationship between cognitive style and change in belief over time. Study 3 revealed such a causal relationship over the short term: Experimentally inducing a mindset that favors intuition over reflection increases self-reported belief in God.

Many important moral decisions, particularly at the policy level, require the evaluation of choic... more Many important moral decisions, particularly at the policy level, require the evaluation of choices involving outcomes of variable magnitude and probability. Many economic decisions involve the same problem. It is not known whether and to what extent these structurally isomorphic decisions rely on common neural mechanisms. Subjects undergoing fMRI evaluated the moral acceptability of sacrificing a single life to save a larger group of variable size and probability of dying without action. Paralleling research on economic decision-making, the ventromedial prefrontal cortex and ventral striatum were specifically sensitive to the “expected moral value” of actions, i.e. the expected number of lives lost/saved. Likewise, the right anterior insula was specifically sensitive to outcome probability. Other regions tracked outcome certainty and individual differences in utilitarian tendency. The present results suggest that complex life-and-death moral decisions that affect others depend on neural circuitry adapted for more basic, self-interested decision-making involving material rewards.

Animal studies have shown that acetylcholine decreases excitatory receptive field size and spread... more Animal studies have shown that acetylcholine decreases excitatory receptive field size and spread of excitation in early visual cortex. These effects are thought to be due to facilitation of thalamocortical synaptic transmission and/or suppression of intracortical connections. We have used functional magnetic resonance imaging (fMRI) to measure the spatial spread of responses to visual stimulation in human early visual cortex. The cholinesterase inhibitor donepezil was administered to normal healthy human subjects to increase synaptic levels of acetylcholine in the brain. Cholinergic enhancement with donepezil decreased the spatial spread of excitatory fMRI responses in visual cortex, consistent with a role of acetylcholine in reducing excitatory receptive field size of cortical neurons. Donepezil also reduced response amplitude in visual cortex, but the cholinergic effects on spatial spread were not a direct result of reduced amplitude. These findings demonstrate that acetylcholine regulates spatial integration in human visual cortex.