The psychophysics of uneconomical choice: non-linear reward evaluation by a nectar feeder

Uneconomical choices by humans or animals that evaluate reward options challenge the expectation that decision-makers always maximize the return currency. One possible explanation for such deviations from optimality is that the ability to sense differences in physical value between available alternatives is constrained by the sensory and cognitive processes for encoding profitability. In this study, we investigated the capacity of a nectarivorous bat species (Glossophaga commissarisi) to discriminate between sugar solutions with different concentrations. We conducted a two-alternative free-choice experiment on a population of wild electronically tagged bats foraging at an array of computer-automated artificial flowers that recorded individual choices. We used a Bayesian approach to fit individual psychometric functions, relating the strength of preferring the higher concentration option to the intensity of the presented stimulus. Psychometric analysis revealed that discrimination ability increases non-linearly with respect to intensity. We combined this result with a previous psychometric analysis of volume perception. Our theoretical analysis of choice for rewards that vary in two quality dimensions revealed regions of parameter combinations where uneconomic choice is expected. Discrimination ability may be constrained by non-linear perceptual and cognitive encoding processes that result in uneconomical choice.     

Anticipation of reward omission as a cue for choice behavior

A within-subject partial reinforcement extinction effect was obtained in a conditional discriminative choice task. In choice acquisition, one group had learned a task in which one choice alternative was continuously reinforced (CRF) and the other alternative was partially reinforced (PRF). Most errors in the acquisition phase were the choosing of the CRF lever when the conditional stimulus signaled the PRF lever; in extinction this pattern of choice errors reversed. In extinction, most errors were choosing of the PRF lever when the conditional stimulus signaled the CRF lever. The predictions of frustration theory and sequential theory were compared with the choice data. The results were interpreted as consistent with the anticipatory frustration construct within an associative mediational theory.     

The inherent tensile strength of iron

The cohesive energy of Fe as a function of structure, strain and magnetic state has been computed using the full potential linearized augmented-plane-wave method within the framework of density functional theory and the generalized gradient approximation. Calculations corresponding to uniaxial stress in the <100> direction reveal that the ideal tensile strength of bcc Fe is about 14.2GPa and is determined by instability with respect to transformation into an unstable ferromagnetic fcc structure. The low-energy fcc phase is a modulatedantiferromagnetic fcc structure that is connected to the bcc phase via a first-order magnetic transformation and does not compromise its ideal strength.     

The reward value of peers

Sixteen socially isolate preschoolers were classified as peer- or non-peer-oriented on the basis of their responses to a test devised to measure the reward value of peers. Half of the subjects in each classification were assigned to a modeling treatment and viewed a film depicting appropriate social behavior in the nursery school; half served as controls and saw an animal film. Peer-oriented modeling film subjects increased significantly more in their peer social interactions at posttest and follow-up assessments than did the non-peer-oriented modeling group. In addition, both peer-oriented and non-peer-oriented modeling groups were significantly higher on peer interaction than the control groups. Alternative and supplemental procedures for increasing isolate preschoolers' social interaction are discussed.     

The reward value of near-miss situations

Svartdal, F. (2011). The reward value of near‐miss situations. Scandinavian Journal of Psychology52, 209–217. What is a “positive” outcome? Clearly, obtaining something attractive is regarded as positive, but so is avoiding something negative. The present paper compared these two types of situations in scenario‐type evaluations. Participants rated positive (P), avoiding negative (AN), and negative (N) outcomes in terms of luck (Experiment 1) and overall positive/negative evaluations (Experiments 2 and 3). The results demonstrated that evaluations of P and AN outcomes were judged as equally positive, but the emotional basis for these evaluations was very different: The feeling of relief was the dominating emotion in AN situations, whereas joy was the dominating emotion in P situations. Overall, these results indicate that avoidance‐induced reward value may be important as a motivating factor in cognition and action.     

The psychological distance to reward

Pigeons' responses in the presence of two concurrently available (initial-link) stimuli produced entry into one of two different and mutually exclusive terminal link stimuli according to identical but independent variable-interval schedules. In one experiment, a two-component chained fixed-interval schedule produced food in one terminal link while a simple fixed-interval schedule produced food in the other terminal link. When the interreinforcement intervals were equal in the two terminal links (i.e., the simple fixed-interval was twice the size of each of the components in the chained schedule) pigeons preferred the simple fixed-interval as measured by their relative rates of responding in the concurrently available initial links. This preference increased as the duration of the terminal links increased. The preference could be reversed by making the simple fixed-interval schedule sufficiently longer than the chained schedule. In the second experiment, the terminal links consisted of two- vs three-component chained fixed-intervals, again with equal interreinforcement intervals. Pigeons preferred the two-component chain to the three-component chain, although these results were less consistent and less dramatic than those in the first experiment. Again, preference increased as the duration of the terminal links increased. The results show that an organism's choice for a schedule will be substantially lowered by the chaining operation even when the interreinforcement interval remains constant.     

Comparative evaluations of reward dimensions in honey bees: evidence from two-alternative forced choice proboscis-extension conditioning

A major challenge in understanding choice behaviour is determining how subjects evaluate alternatives that differ along multiple dimensions. Of particular interest is whether similar dimensions are compared to each other or whether each alternative is assigned an absolute value (utility). We assumed that choice proportions would follow Weber’s effect, according to which discrimination is proportional to relative difference (difference/mean). We tested honey bees in a two-alternative forced choice (2AFC) paradigm of proboscis-extension response (PER) conditioning. Subjects were conditioned over six trials to associate each of two odours with sucrose solution rewards and then tested in a choice trial between the two alternatives. Each group of subjects was tested in one treatment, and there were four treatments in each of six experiments. Rewards differed in delay, duration of feeding, and sucrose concentration. In each treatment, the high-profitability alternative was better than the low-profitability alternative along a single dimension, but between treatments of each experiment values in another dimension monotonically increased. Proboscis-response proportions during the conditioning phase tended to be greater for the high-profitability alternative, and choice proportions for it in the choice phase ranged between 0.72 and 0.89 in the 24 treatments. We show for the first time that harnessed bees are sensitive to reward delay. Preferences did not differ statistically between the different treatments of any of the experiments. The results support comparative evaluation of alternatives and are pertinent to multi-attribute choice, with implications for context-dependent preferences. We also discuss the potential advantages of the 2AFC PER simultaneous choice assay.     

The inherent limits of predicting school violence.

The recent media hype over school shootings has led to demands for methods of identifying school shooters before they act. Despite the fact that schools remain one of the safest places for youths to be, schools are beginning to adopt identification systems to determine which students could be future killers. The methods used to accomplish this not only are unproven but are inherently limited in usefulness and often do more harm than good for both the children and the school setting. The authors' goals in the present article are to place school shootings in perspective relative to other risks of violence that children face and to provide a reasonable and scientifically defensible approach to improving the safety of schools.     

The amygdala, reward and emotion

Recent research provides new insights into amygdala contributions to positive emotion and reward. Studies of neuronal activity in the monkey amygdala and of autonomic responses mediated by the monkey amygdala show that, contrary to a widely held view, the amygdala is just as important for processing positive reward and reinforcement as it is for negative. In addition, neuropsychological studies reveal that the amygdala is essential for only a fraction of what might be considered 'stimulus-reward processing', and that the neural substrates for emotion and reward are partially nonoverlapping. Finally, evidence suggests that two systems within the amygdala, operating in parallel, enable reward-predicting cues to influence behavior; one mediates a general, arousing effect of reward and the other links the sensory properties of reward to emotion.     

The differential influences of positive affect,random reward,and performance-contingent reward on cognitive control

Growing evidence suggests that positive affect and reward have differential effects on cognitive control. So far, however, these effects have never been studied together. Here, the authors present one behavioral study investigating the influences of positive affect and reward (contingent and noncontingent) on proactive control. A modified version of the AX-continuous performance task, which has repeatedly been shown to be sensitive to reward and affect manipulations, was used. In a first phase, two experimental groups received either neutral or positive affective pictures before every trial. In a second phase, the two halves of a given affect group additionally received, respectively, performance-contingent or random rewards. The results replicated the typical affect effect, in terms of reduced proactive control under positive as compared to neutral affect. Also, the typical reward effects associated with increased proactive control were replicated. Most interestingly, performance-contingent reward counteracted the positive affect effect, whereas random reward mirrored that effect. In sum, this study provides first evidence that performance-contingent reward, on the one hand, and positive affect and performance-noncontingent reward, on the other hand, have oppositional effects on cognitive control: Only performance-contingent reward showed a motivational effect in terms of a strategy shift toward increased proactive control, whereas positive affect alone and performance-noncontingent reward reduced proactive control. Moreover, the integrative design of this study revealed the vulnerability of positive affect effects to motivational manipulations. The results are discussed with respect to current neuroscientific theories of the effects of dopamine on affect, reward, and cognitive control.     

The reward probability index: design and validation of a scale measuring access to environmental reward

Behavioral models of depression implicate decreased response-contingent positive reinforcement (RCPR) as critical toward the development and maintenance of depression (Lewinsohn, 1974). Given the absence of a psychometrically sound self-report measure of RCPR, the Reward Probability Index (RPI) was developed to measure access to environmental reward and to approximate actual RCPR. In Study 1 (n = 269), exploratory factor analysis supported a 20-item two-factor model (Reward Probability, Environmental Suppressors) with strong internal consistency (α = .90). In Study 2 (n = 281), confirmatory factor analysis supported this two-factor structure and convergent validity was established through strong correlations between the RPI and measures of activity, avoidance, reinforcement, and depression (r = .65 to .81). Discriminant validity was supported via smaller correlations between the RPI and measures of social support and somatic anxiety (r = – .29 to – .40). Two-week test–retest reliability was strong (r = .69). In Study 3 (n = 33), controlling for depression symptoms, hierarchical regression supported the incremental validity of the RPI in predicting daily diary reports of environmental reward. The RPI represents a parsimonious, reliable, and valid measure that may facilitate understanding of the etiology of depression and its relationship to overt behaviors.     

The prediction of choice

This paper is concerned with a central concept in social measurement such as opinion polls, the measurement of attitudes, the prediction of political elections, the measurement of moral values, the measurement of consumer preferences, the measurement of utility, and the measurement of aesthetic values. The concept is that of the discriminal dispersion and its interesting effects in the prediction of choice.