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Benjamin Hayden

    Benjamin Hayden

    Abstract 1. Uncertainty is ubiquitous, and adaptive behavior requires dealing with it in a biologically meaningful fashion. Our goal in this chapter is to describe current evidence concerning the mechanisms that allow decision makers to... more
    Abstract 1. Uncertainty is ubiquitous, and adaptive behavior requires dealing with it in a biologically meaningful fashion. Our goal in this chapter is to describe current evidence concerning the mechanisms that allow decision makers to deal with the uncertainty that characterizes our world. A fundamental premise is that these mechanisms are embodied in neuronal and chemical events in the brain. We therefore advocate a neuroeconomic approach to understanding the mechanisms of risk-sensitive decision making. This ...
    Studies of animal impulsivity generally find steep subjective devaluation, or discounting, of delayed rewards - often on the order of a 50% reduction in value in a few seconds. Because such steep discounting is highly disfavored in... more
    Studies of animal impulsivity generally find steep subjective devaluation, or discounting, of delayed rewards - often on the order of a 50% reduction in value in a few seconds. Because such steep discounting is highly disfavored in evolutionary models of time preference, we hypothesize that discounting tasks provide a poor measure of animals' true time preferences. One prediction of this hypothesis is that estimates of time preferences based on these tasks will lack external validity, i.e. fail to predict time preferences in other contexts. We examined choices made by four rhesus monkeys in a computerized patch-leaving foraging task interleaved with a standard intertemporal choice task. Monkeys were significantly more patient in the foraging task than in the intertemporal choice task. Patch-leaving behavior was well fit by parameter-free optimal foraging equations but poorly fit by the hyperbolic discount parameter obtained from the intertemporal choice task. Day-to-day variatio...
    Recent theories suggest that reward-based choice reflects competition between value signals in the ventromedial prefrontal cortex (vmPFC). We tested this idea by recording vmPFC neurons while macaques performed a gambling task with... more
    Recent theories suggest that reward-based choice reflects competition between value signals in the ventromedial prefrontal cortex (vmPFC). We tested this idea by recording vmPFC neurons while macaques performed a gambling task with asynchronous offer presentation. We found that neuronal activity shows four patterns consistent with selection via mutual inhibition: (1) correlated tuning for probability and reward size, suggesting that vmPFC carries an integrated value signal; (2) anti-correlated tuning curves for the two options, suggesting mutual inhibition; (3) neurons rapidly come to signal the value of the chosen offer, suggesting the circuit serves to produce a choice; and (4) after regressing out the effects of option values, firing rates still could predict choice-a choice probability signal. In addition, neurons signaled gamble outcomes, suggesting that vmPFC contributes to both monitoring and choice processes. These data suggest a possible mechanism for reward-based choice an...
    The St. Petersburg Paradox is a famous economic and philosophical puzzle that has generated numerous conflicting explanations. To shed empirical light on this phenomenon, we examined subjects' bids for one St. Petersburg gamble with a... more
    The St. Petersburg Paradox is a famous economic and philosophical puzzle that has generated numerous conflicting explanations. To shed empirical light on this phenomenon, we examined subjects' bids for one St. Petersburg gamble with a real monetary payment. We found that bids were typically lower than twice the smallest payoff, and thus much lower than is generally supposed. We also examined bids offered for several hypothetical variants of the St. Petersburg Paradox. We found that bids were weakly affected by truncating the gamble, were strongly affected by repeats of the gamble, and depended linearly on the initial "seed" value of the gamble. One explanation, which we call the median heuristic, strongly predicts these data. Subjects following this strategy evaluate a gamble as if they were taking the median rather than the mean of the payoff distribution. Finally, we argue that the distribution of outcomes embodied in the St. Petersburg paradox is so divergent from t...
    Humans and other animals are idiosyncratically sensitive to risk, either preferring or avoiding options having the same value but differing in uncertainty. Many explanations for risk sensitivity rely on the non-linear shape of a... more
    Humans and other animals are idiosyncratically sensitive to risk, either preferring or avoiding options having the same value but differing in uncertainty. Many explanations for risk sensitivity rely on the non-linear shape of a hypothesized utility curve. Because such models do not place any importance on uncertainty per se, utility curve-based accounts predict indifference between risky and riskless options that offer the same distribution of rewards. Here we show that monkeys strongly prefer uncertain gambles to alternating rewards with the same payoffs, demonstrating that uncertainty itself contributes to the appeal of risky options. Based on prior observations, we hypothesized that the appeal of the risky option is enhanced by the salience of the potential jackpot. To test this, we subtly manipulated payoffs in a second gambling task. We found that monkeys are more sensitive to small changes in the size of the large reward than to equivalent changes in the size of the small rew...
    Humans may be patient when it comes to money, but chimpanzees are willing to wait longer than humans for food, suggesting patience is neither innate nor uniquely human.
    Abstract Functional magnetic resonance imaging (fMRI) and single unit physiology are two of the most widely-used methods in cognitive neuroscience and neuroeconomics. Despite the fact that practitioners of both methods share a common... more
    Abstract Functional magnetic resonance imaging (fMRI) and single unit physiology are two of the most widely-used methods in cognitive neuroscience and neuroeconomics. Despite the fact that practitioners of both methods share a common goal–understanding the mechanisms underlying behavior and cognition–their efforts are rarely directly linked. Here we consider some of the reasons for apparent discrepancies between findings of fMRI and electrophysiological studies. We examine these problems through the lens of two case ...
    Attention can facilitate visual processing, emphasizing specific locations and highlighting stimuli containing specific features. To dissociate the mechanisms of spatial and feature-based attention, we compared the time course of visually... more
    Attention can facilitate visual processing, emphasizing specific locations and highlighting stimuli containing specific features. To dissociate the mechanisms of spatial and feature-based attention, we compared the time course of visually evoked responses under different attention conditions. We recorded from single neurons in area V4 during a delayed match-to-sample task that controlled both spatial and feature-based attention. Neuronal responses increased when spatial attention was directed toward the receptive field and were modulated by the identity of the target of feature-based attention. Modulation by spatial attention was weaker during the early portion of the visual response and stronger during the later portion of the response. In contrast, modulation by feature-based attention was relatively constant throughout the response. It appears that stimulus onset transients disrupt spatial attention, but not feature attention. We conclude that spatial attention reflects a combina...
    Humans find members of the opposite sex more attractive when their image is spatially associated with the color red. This effect even occurs when the red color is not on the skin or clothing (i.e. is extraneous). We hypothesize that this... more
    Humans find members of the opposite sex more attractive when their image is spatially associated with the color red. This effect even occurs when the red color is not on the skin or clothing (i.e. is extraneous). We hypothesize that this extraneous color effect could be at least partially explained by a low-level and biologically innate generalization process, and so similar extraneous color effects should be observed in non-humans. To test this possibility, we examined the influence of extraneous color in rhesus macaques (Macaca mulatta). Across two experiments, we determined the influence of extraneous red on viewing preferences (assessed by looking time) in free-ranging rhesus monkeys. We presented male and female monkeys with black and white photographs of the hindquarters of same and opposite sex conspecifics on either a red (experimental condition) or blue (control condition) background. As a secondary control, we also presented neutral stimuli (photographs of seashells) on re...
    Despite the fact that early hypometabolism and neural degeneration in posterior cingulate cortex (CGp) predict cognitive decline in Alzheimer's disease, and CGp hyperactivity predicts cognitive dysfunction in schizophrenia as well as... more
    Despite the fact that early hypometabolism and neural degeneration in posterior cingulate cortex (CGp) predict cognitive decline in Alzheimer's disease, and CGp hyperactivity predicts cognitive dysfunction in schizophrenia as well as first-degree relatives, the function of this brain area remains unclear. The disparate evidence for CGp involvement in a variety of cognitive and behavioral processes has belied any simple functional description. Here we develop a new model that proposes that CGp integrates the recent history of rewards, ...
    Efficiently shifting between tasks is a central function of cognitive control. The role of the default network - a constellation of areas with high baseline activity that declines during task performance - in cognitive control remains... more
    Efficiently shifting between tasks is a central function of cognitive control. The role of the default network - a constellation of areas with high baseline activity that declines during task performance - in cognitive control remains poorly understood. We hypothesized that task switching demands cognitive control to shift the balance of processing toward the external world, and therefore predicted that switching between the two tasks would require suppression of activity of neurons within the posterior cingulate cortex (CGp). To test this idea, we recorded the activity of single neurons in CGp, a central node in the default network, in monkeys performing two interleaved tasks. As predicted, we found that basal levels of neuronal activity were reduced following a switch from one task to another and gradually returned to pre-switch baseline on subsequent trials. We failed to observe these effects in lateral intraparietal cortex, part of the dorsal fronto-parietal cortical attention n...
    The core feature of an economic exchange is a decision to trade one good for another, based on a comparison of relative value. Economists have long recognized, however, that the value an individual ascribes to a good during decision... more
    The core feature of an economic exchange is a decision to trade one good for another, based on a comparison of relative value. Economists have long recognized, however, that the value an individual ascribes to a good during decision making (i.e., their relative willingness to trade for that good) does not always map onto the reward they actually experience. Here, we show that experienced value and decision value are represented in distinct regions of ventromedial prefrontal cortex (VMPFC) during the passive consumption of rewards. Participants viewed two categories of rewards-images of faces that varied in their attractiveness and monetary gains and losses-while being scanned using functional magnetic resonance imaging. An independent market task, in which participants exchanged some of the money that they had earned for brief views of attractive faces, determined the relative decision value associated with each category. We found that activation of anterior VMPFC increased with increasing experienced value, but not decision value, for both reward categories. In contrast, activation of posterior VMPFC predicted each individual's relative decision value for face and monetary stimuli. These results indicate not only that experienced value and decision value are represented in distinct regions of VMPFC, but also that decision value signals are evident even in the absence of an overt choice task. We conclude that decisions are made by comparing neural representations of the value of different goods encoded in posterior VMPFC in a common, relative currency.
    Although still in the early stages, neuroeconomics—the union of ethology, economics, and neuroscience—offers a potentially powerful way to study the neural mechanisms underlying reward, punishment, and decision making, as well as the... more
    Although still in the early stages, neuroeconomics—the union of ethology, economics, and neuroscience—offers a potentially powerful way to study the neural mechanisms underlying reward, punishment, and decision making, as well as the dysfunction of these systems in pathological conditions such as addiction. These neural processes interact in important ways with systems evaluating social context and uncertainty, and their study may lead to potent insights and testable predictions relevant to the neurobiology of addiction. ...
    The neural mechanisms supporting the ability to recognize and respond to fictive outcomes, outcomes of actions that one has not taken, remain obscure. We hypothesized that neurons in the anterior cingulate cortex (ACC), which monitors the... more
    The neural mechanisms supporting the ability to recognize and respond to fictive outcomes, outcomes of actions that one has not taken, remain obscure. We hypothesized that neurons in the anterior cingulate cortex (ACC), which monitors the consequences of actions and mediates subsequent changes in behavior, would respond to fictive reward information. We recorded responses of single neurons during performance of a choice task that provided information about the reward values of options that were not chosen. We ...