Giles Story

Humans frequently need to allocate resources across multiple time-steps. Economic theory proposes that subjects do so according to a stable set of intertemporal preferences, but the computational demands of such decisions encourage the use of formally less competent heuristics. Few empirical studies have examined dynamic resource allocation decisions systematically. Here we conducted an experiment involving the dynamic consumption over approximately 15 minutes of a limited budget of relief from moderately painful stimuli. We had previously elicited the participants' time preferences for the same painful stimuli in one-off choices, allowing us to assess self-consistency. Participants exhibited three characteristic behaviors: saving relief until the end, spreading relief across time, and early spending, of which the last was markedly less prominent. The likelihood that behavior was heuristic rather than normative is suggested by the weak correspondence between one-off and dynamic choices. We show that the consumption choices are consistent with a combination of simple heuristics involving early-spending, spreading or saving of relief until the end, with subjects predominantly exhibiting the last two. People often have to trade-off their present wellbeing against their future wellbeing, for example whether to go to an expensive restaurant today or put the money towards a future holiday. Many studies have examined how people make such trade-offs. However, the majority have done so by analyzing choices between one-off future outcomes. By contrast, real-world choices are often made sequentially, with today's choices influencing the possibilities available tomorrow. This generates decision problems of near limitless complexity. To explore how people approach such decisions in a naturalistic (health-related) setting, we describe participants' use of a limited budget of relief from moderately painful stimuli over a period of approximately 15 minutes. Participants showed a range of different

Red or processed meat, but not white meat or fish, is associated with colorectal cancer. The endogenous formation of nitroso compounds is a possible explanation, as red or processed meat—but not white meat or fish—causes a dose-dependent increase in fecal apparent total N-nitroso compounds (ATNC) and the formation of nitroso-compound-specific DNA adducts. Red meat is particularly rich in heme and heme has also been found to promote the formation of ATNC. To investigate the underlying mechanism of ATNC formation, fecal and ileal samples of volunteers fed a high red meat or a vegetarian diet were analyzed for nitrosyl iron, nitrosothiols, and heme. To simulate the processes in the stomach, food homogenates and hemoglobin were incubated under simulated gastric conditions. Nitrosyl iron and nitrosothiols were significantly (p < 0.0001) increased in ileal and fecal samples after a high red meat diet compared with a vegetarian diet; significantly more nitrosyl iron than nitrosothiols was detectable in ileal (p < 0.0001) and fecal (p < 0.001) samples. The strong correlation between fecal nitrosyl iron and heme (0.776; p < 0.0001) suggested that nitrosyl heme is the main source of nitrosyl iron, and ESR confirmed the presence of nitrosyl heme in fecal samples after a high red meat diet. Under simulated gastric conditions, mainly nitrosothiols were formed, suggesting that acid-catalyzed thionitrosation is the initial step in the endogenous formation of nitroso compounds. Nitrosyl heme and other nitroso compounds can then form under the alkaline and reductive conditions of the small and large bowel.

Standard theories of decision-making involving delayed outcomes predict that people should defer a punishment, whilst advancing a reward. In some cases, such as pain, people seem to prefer to expedite punishment, implying that its anticipation carries a cost, often conceptualized as 'dread'. Despite empirical support for the existence of dread, whether and how it depends on prospective delay is unknown. Furthermore, it is unclear whether dread represents a stable component of value, or is modulated by biases such as framing effects. Here, we examine choices made between different numbers of painful shocks to be delivered faithfully at different time points up to 15 minutes in the future, as well as choices between hypothetical painful dental appointments at time points of up to approximately eight months in the future, to test alternative models for how future pain is disvalued. We show that future pain initially becomes increasingly aversive with increasing delay, but does so at a decreasing rate. This is consistent with a value model in which moment-by-moment dread increases up to the time of expected pain, such that dread becomes equivalent to the discounted expectation of pain. For a minority of individuals pain has maximum negative value at intermediate delay, suggesting that the dread function may itself be prospectively discounted in time. Framing an outcome as relief reduces the overall preference to expedite pain, which can be parameterized by reducing the rate of the dread-discounting function. Our data support an account of disvaluation for primary punishments such as pain, which differs fundamentally from existing models applied to financial punishments, in which dread exerts a powerful but time-dependent influence over choice.

An aversion to harming others is a core component
of human morality and is disturbed in antisocial
behavior [1–4]. Deficient harm aversion
may underlie instrumental and reactive aggression,
which both feature in psychopathy [5]. Past
work has highlighted monoaminergic influences
on aggression [6–11], but a mechanistic account
of how monoamines regulate antisocial motives
remains elusive. We previously observed that
most people show a greater aversion to inflicting
pain on others than themselves [12]. Here, we
investigated whether this hyperaltruistic disposition
is susceptible to monoaminergic control. We
observed dissociable effects of the serotonin reuptake
inhibitor citalopram and the dopamine
precursor levodopa on decisions to inflict pain
on oneself and others for financial gain. Computational
models of choice behavior showed that
citalopram increased harm aversion for both self
and others, while levodopa reduced hyperaltruism.
The effects of citalopram were stronger than those
of levodopa. Crucially, neither drug influenced the
physical perception of pain or other components
of choice such as motor impulsivity or loss aversion
[13, 14], suggesting a direct and specific influence
of serotonin and dopamine on the valuation
of harm. We also found evidence for dose
dependency of these effects. Finally, the drugs
had dissociable effects on response times, with
citalopram enhancing behavioral inhibition and
levodopa reducing slowing related to being responsible
for another’s fate. These distinct roles
of serotonin and dopamine in modulating moral
behavior have implications for potential treatments
of social dysfunction that is a common
feature as well as a risk factor for many psychiatric
disorders

People show empathic responses to others' pain, yet how they choose to apportion pain between themselves and others is not well understood. To address this question, we observed choices to reapportion social allocations of painful stimuli and, for comparison, also elicited equivalent choices with money. On average people sought to equalize allocations of both pain and money, in a manner which indicated that inequality carried an increasing marginal cost. Preferences for pain were more altruistic than for money, with several participants assigning more than half the pain to themselves. Our data indicate that, given concern for others, the fundamental principle of diminishing marginal utility motivates spreading costs across individuals. A model incorporating this assumption outperformed existing models of social utility in explaining the data. By implementing selected allocations for real, we also found that while inequality per se did not influence pain perception, altruistic behavior had an intrinsic analgesic effect for the recipient. Social inequality is a near universal feature of human experience. Nevertheless, people often appear motivated to reduce inequality, for example increased wealth drives charitable action 1,2 , and relative poverty is associated with acquisitive crime 3. A teleological explanation for such behavior is that people are concerned with achieving a fair (equitable) social distribution of benefits 4. The latter is often approximated as a subjective cost associated with having either more or fewer resources than others, termed inequality aversion 5–9. Many experimental studies have examined how humans redress monetary inequality. A common observation is that within a scenario referred to as the 'dictator game' , people endowed with money frequently share a portion with others in the absence of direct return for themselves 2,4,10,11. Similarly people will take money from those endowed with more money than themselves 10,12. By contrast, how humans respond to unequal allocations of pain between themselves and others is little studied. Commensurate with documented empathic responses to pain in others 13–15 , participants take on painful stimuli to relieve the apparent suffering of a confederate 16,17. Furthermore, a study implementing a dictator game with painful outcomes found that participants were particularly egalitarian, allocating on average 48% of the pain (time spent immersing one's hand in ice water) to themselves, while in a monetary dictator game the same participants were significantly less charitable, donating only 30% of the endowment on average 18. These findings might suggest that people are more inequality-averse for pain than money, in other words that people particularly dislike having either more or less pain than others. However an alternative possibility is that people are simply more altruistic for pain than for money, in the sense that relieving others' of their physical suffering carries greater motivational weight than does increasing others' wealth.

Impatience for reward is a facet of many psychiatric disorders. We draw attention to a growing literature finding greater discounting of delayed reward, an important aspect of impatience, across a range of psychiatric disorders. We propose these findings are best understood by considering the goals and motivation for discounting future reward. We characterize these as arising from either the opportunity costs of waiting or the uncertainty associated with delayed reward. We link specific instances of higher discounting in psychiatric disorder to heightened subjective estimates of either of these factors. We propose these costs are learned and represented based either on a flexible cognitive model of the world, an accumulation of previous experience, or through evolutionary specification. Any of these can be considered suboptimal for the individual if the resulting behavior results in impairments in personal and social functioning and/or in distress. By considering the neurochemical and neuroanatomical implementation of these processes, we illustrate how this approach can in principle unite social, psychological and biological conceptions of impulsive choice.

The tendency to make unhealthy choices is hypothesized to be related to an individual's temporal discount rate, the theoretical rate at which they devalue delayed rewards. Furthermore, a particular form of temporal discounting, hyperbolic discounting, has been proposed to explain why unhealthy behavior can occur despite healthy intentions. We examine these two hypotheses in turn. We first systematically review studies which investigate whether discount rates can predict unhealthy behavior. These studies reveal that high discount rates for money (and in some instances food or drug rewards) are associated with several unhealthy behaviors and markers of health status, establishing discounting as a promising predictive measure. We secondly examine whether intention-incongruent unhealthy actions are consistent with hyperbolic discounting. We conclude that intention-incongruent actions are often triggered by environmental cues or changes in motivational state, whose effects are not parameterized by hyperbolic discounting. We propose a framework for understanding these state-based effects in terms of the interplay of two distinct reinforcement learning mechanisms: a " model-based " (or goal-directed) system and a " model-free " (or habitual) system. Under this framework, while discounting of delayed health may contribute to the initiation of unhealthy behavior, with repetition, many unhealthy behaviors become habitual; if health goals then change, habitual behavior can still arise in response to environmental cues. We propose that the burgeoning development of computational models of these processes will permit further identification of health decision-making phenotypes.

Research into the biological basis of emotional and motivational disorders is in danger of riding roughshod over a patient-centered psychiatry and falling into the dualist errors of the past, i.e., by treating mind and brain as conceptually distinct. We argue that a psychiatry informed by computational neuroscience, computational psychiatry, can obviate this danger. Through a focus on the reasoning processes by which humans attempt to maximize reward (and minimize punishment), and how such reasoning is expressed neurally, computational psychiatry can render obsolete the polarity between biological and psychosocial conceptions of illness. Here, the term 'psychological' comes to refer to information processing performed by biological agents, seen in light of underlying goals. We reflect on the implications of this perspective for a definition of mental disorder, including what is entailed in asserting that a particular disorder is 'biological' or 'psychological' in origin. We propose that a computational approach assists in understanding the topography of mental disorder, while cautioning that the point at which eccentric reasoning constitutes disorder often remains a matter of cultural judgment.

When people anticipate uncertain future outcomes, they often prefer to know their fate in advance. Inspired by an idea in behavioral economics that the anticipation of rewards is itself attractive, we hypothesized that this preference of advance information arises because reward prediction errors carried by such information can boost the level of anticipation. We designed new empirical behavioral studies to test this proposal, and confirmed that subjects preferred advance reward information more strongly when they had to wait for rewards for a longer time. We formulated our proposal in a reinforcement-learning model, and we showed that our model could account for a wide range of existing neuronal and behavioral data, without appealing to ambiguous notions such as an explicit value for information. We suggest that such boosted anticipation significantly drives risk-seeking behaviors, most pertinently in gambling.

Background Studies using conventional consoles have suggested a possible link between video-gaming and laparoscopic skill. The authors hypothesized that the Nintendo Wii, with its motion-sensing interface, would provide a better model for laparoscopic tasks. This study investigated the relationship between Nintendo Wii skill, prior gaming experience, and laparoscopic skill. Methods In this study, 20 participants who had minimal experience with either laparoscopic surgery or Nintendo Wii performed three tasks on a Webcam-based laparoscopic simulator and were assessed on three games on the Wii. The participants completed a questionnaire assessing prior gaming experience. Results The score for each of the three Wii games correlated positively with the laparoscopic score (r = 0.78, 0.63, 0.77; P r = 0.82; P P r = 0.713; P r = 0.578; P P = 0.26). Conclusions The study findings suggest a skill overlap between the Nintendo Wii and basic laparoscopic tasks. Surgical candidates with advanced Nintendo Wii ability may possess higher baseline laparoscopic ability.

Saccadic latencies have long been known to depend on the relative timing of the appearance of the new target, and offset of the original fixation target. Previous studies have tended to conclude that two separate effects are at work, one equivalent to competitive inhibition from the fixation target, and the other due to its offset providing a warning that shortens latency. In this study, we propose a simpler explanation, based on a well-established model of reaction time, LATER (linear approach to threshold with ergodic rate), that in addition to predicting mean latencies also—more challengingly—predicts latency distributions. We show that observed distributions, using gap, step and appearance tasks under three conditions of prior probability, can be accurately predicted by using a pair of LATER units, one corresponding to fixation target offset and the other to peripheral target onset. Because fixation offset is probabilistically associated with target appearance, when the fixation unit is activated it increases the target’s decision signal (that represents probability) in a fixed proportion, speeding responses. In contrast, when the fixation target remains present, the fixation unit is not activated, and responses are slower. Both these effects generate characteristic changes in the shapes of the latency distributions that can be accurately predicted by the model.