Human risky choice under temporal constraints: tests of an energy-budget model

Risk-sensitive foraging models predict that choice between fixed and variable food delays should be influenced by an organism's energy budget. To investigate whether the predictions of these models could be extended to choice in humans, risk sensitivity in 4 adults was investigated under laboratory conditions designed to model positive and negative energy budgets. Subjects chose between fixed and variable trial durations with the same mean value. An energy requirement was modeled by requiring that five trials be completed within a limited time period for points delivered at the end of the period (block of trials) to be exchanged later for money. Manipulating the duration of this time period generated positive and negative earnings budgets (or, alternatively, "time budgets"). Choices were consistent with the predictions of energy-budget models: The fixed-delay option was strongly preferred under positive earnings-budget conditions and the variable-delay option was strongly preferred under negative earnings-budget conditions. Within-block (or trial-by-trial) choices were also frequently consistent with the predictions of a dynamic optimization model, indicating that choice was simultaneously sensitive to the temporal requirements, delays associated with fixed and variable choices on the upcoming trial, cumulative delays within the block of trials, and trial position within a block.     

Pigeons' preference for variable-interval water reinforcement under widely varied water budgets.

Water budget of pigeons was varied to assess the dependence of risk-sensitive preferences upon economic context such as has been reported for energy-budget manipulations with small animals in behavioral ecology research. Fixed- and variable-interval terminal-link water schedules reinforced choice between equal variable-interval initial-link schedules arranged on two pecking keys. While keeping a severely restrictive budget the same across three phases of the experiment, a contrasting distinct ample budget was arranged in each. To mimic typical methods in behavioral ecology studies, in each ample budget a more than three-fold increase in amount of water per reinforcer presentation was instituted simultaneously with significantly increased overall access to water. Total choice response rates plummeted in the ample budgets, and body weights either increased significantly or remained unchanged in different phases as expected by the nature of the different manipulations. Clear preferences for the variable-interval schedule were found throughout the experiment, except for rare instances of key bias. The results agree with similar operant food-reinforcement studies and extend conditions under which risk preference apparently does not depend upon economic context.     

RISKY CHOICE IN PIGEONS: PREFERENCE FOR AMOUNT VARIABILITY USING A TOKEN-REINFORCEMENT SYSTEM

Pigeons were given repeated choices between variable and fixed numbers of token reinforcers (stimulus lamps arrayed above the response keys), with each earned token exchangeable for food. The number of tokens provided by the fixed‐amount option remained constant within blocks of sessions, but varied parametrically across phases, assuming values of 2, 4, 6, or 8 tokens per choice. The number of tokens provided by the variable‐amount option varied between 0 and 12 tokens per choice, arranged according to an exponential or rectangular distribution. In general, the pigeons strongly preferred the variable option when the fixed option provided equal or greater numbers of tokens than the variable amount. Preference for the variable amount decreased only when the alternatives provided widely disparate amounts favoring the fixed amount. When tokens were removed from the experimental context, preference for the variable option was reduced or eliminated, suggesting that the token presentation played a key role in maintaining risk‐prone choice patterns. Choice latencies varied inversely with preferences, suggesting that local analyses may provide useful ancillary measures of reinforcer value. Overall, the results indicate that systematic risk sensitivity can be attained with respect to reinforcer amount, and that tokens may be critical in the development of such preferences.     

Framing Effects: Dynamics and Task Domains

The author examines the mechanisms and dynamics of framing effects in risky choices across three distinct task domains (i.e., life–death, public property, and personal money). The choice outcomes of the problems presented in each of the three task domains had a binary structure of a sure thing vs a gamble of equal expected value; the outcomes differed in their framing conditions and the expected values, raging from 6000, 600, 60, to 6, numerically. It was hypothesized that subjects would become more risk seeking, if the sure outcome was below their aspiration level (the minimum requirement). As predicted, more subjects preferred the gamble when facing the life–death choice problems than facing the counterpart problems presented in the other two task domains. Subjects’ risk preference varied categorically along the group size dimension in the life–death domain but changed more linearly over the expected value dimension in the monetary domain. Framing effects were observed in 7 of 13 pairs of problems, showing a positive frame–risk aversion and negative frame–risk seeking relationship. In addition, two types of framing effects were theoretically defined and empirically identified. Abidirectional framing effectinvolves a reversal in risk preference, and occurs when a decision maker's risk preference is ambiguous or weak. Four bidirectional effects were observed; in each case a majority of subjects preferred the sure outcome under a positive frame but the gamble under a negative frame. In contrast, aunidirectional framing effectrefers to a preference shift due to the framing of choice outcomes: A majority of subjects preferred one choice outcome (either the sure thing or the gamble) under both framing conditions, with positive frame augmented the preference for the sure thing and negative frame augmented the preference for the gamble. These findings revealed some dynamic regularities of framing effects and posed implications for developing predictive and testable models of human decision making.     

Sex differences in risk sensitivity under positive and negative budgets and predictors of choice

The authors investigated sex differences in human risk sensitivity by using a computerized choice task with an energy budget analogue. In addition, they explored possible personality predictors of variance sensitivity. The authors modified the traditional energy budget model from those used in risk-sensitive foraging research with nonhuman animals for appropriate use with a human population. Participants chose between 2 computer icons, 1 yielding a fixed-point reward and the other offering variable points. Men were risk prone in the negative budget and risk averse in the positive budget. Women were risk averse in the negative budget. Personality was not predictive of risk-sensitive bias. Interpreting the results using an evolutionary model, the authors found support for a biological and environmental construct of risk-sensitive behavior.     

自我框架、风险认知和风险选择

对行为决策中“框架效应”(Framing Effect)的研究进行了拓展：探讨了自我框架对风险决策的影响及其机制。面对运用图示方法表示的管理,健康,及投资方面的风险决策问题,参与者自主地选择对方案的描述（自我框架）。研究有四个主要发现：1）自我框架对风险选择的效应部分显著,而且对风险选择的影响方向因情境的不同而不同;2）机会威胁认知是自我框架效应的一个中介变量;3）自我框架在情绪语气上的差异对风险决策有显著影响：决策者对一个备选方案（确定性或风险性方案）相对于另一个备选方案的自我描述的情绪语气越积极正面,这个方案被选择的可能性越大;4）决策者的机会-威胁认知是这一自我框架效应的部分中介变量。也就是说,对备选方案的自我描述语气作为一种对决策信息的编码影响了风险（机会和威胁）认知,进而影响决策者的风险偏好和选择     

Choice between constant and variable alternatives by rats: effects of different reinforcer amounts and energy budgets

Two experiments, using rats as subjects, investigated the effect of different reinforcer amounts and energy budgets on choice between constant and variable alternatives under a closed economy. Rats were housed in the chamber and were exposed to a modified concurrent-chains schedule in which the choice phase was separated from a rest phase during which the rats could engage in other activities. In the choice phase, a single variable-interval schedule arranged entry into one of two equal terminal links (fixed-interval schedules). The constant terminal link ended with the delivery of a fixed number of food pellets (two or three, depending on the condition), whereas the variable terminal link ended with a variable number of food pellets (means of two or three, depending on the condition). Energy budget was defined as positive when body weights were over 90% of free-feeding weights, and as negative when they were under 80% of free-feeding weights. The different body weights were produced by varying the duration of the equal terminal-link schedules within daily 3-hr sessions. In Experiment 1, rats chose between a constant and a variable three pellets under both energy budgets. Rats preferred the constant three pellets more under the positive energy budget, whereas they were indifferent under the negative energy budget. In Experiment 2, rats chose between a constant three pellets and a variable two pellets, and chose between a constant two pellets and a variable three pellets under both energy budgets. The rats strongly preferred the constant three pellets over the variable two pellets under both energy budgets. In contrast, rats preferred the variable three pellets over the constant two pellets only under the negative energy budget, whereas they were indifferent under the positive energy budget. These results indicate that rats choices are sensitive to the difference in reinforcer amounts and to the energy budgets defined by the level of body weight. The present results are consistent with those obtained with small granivorous birds as well as with the predictions of a recent risk-sensitive foraging theory.     

RISKY CHOICE IN PIGEONS AND HUMANS: A CROSS‐SPECIES COMPARISON

Pigeon and human subjects were given repeated choices between variable and adjusting delays to token reinforcement that titrated in relation to a subject's recent choice patterns. Indifference curves were generated under two different procedures: immediate exchange, in which a token earned during each trial was exchanged immediately for access to the terminal reinforcer (food for pigeons, video clips for humans), and delayed exchange, in which tokens accumulated and were exchanged after 11 trials. The former was designed as an analogue of procedures typically used with nonhuman subjects, the latter as an analogue to procedures typically used with human participants. Under both procedure types, different variable‐delay schedules were manipulated systematically across conditions in ways that altered the reinforcer immediacy of the risky option. Under immediate‐exchange conditions, both humans and pigeons consistently preferred the variable delay, and indifference points were generally ordered in relation to relative reinforcer immediacies. Such risk sensitivity was greatly reduced under delayed‐exchange conditions. Choice and trial‐initiation response latencies varied directly with indifference points, suggesting that local analyses may provide useful ancillary measures of reinforcer value. On the whole, the results indicate that modifying procedural features brings choices of pigeons and humans into better accord, and that human—nonhuman differences on risky choice procedures reported in the literature may be at least partly a product of procedural differences.     

Choice,Rating, and Ranking: Framing Effects with Different Response Modes

In a typical risky choice framing task, people have to choose among two options, which are either positively or negatively framed. Choices in the two framing conditions are then compared. However, different preferences between the conditions can be due to changes in the evaluation of the single constituent options or due to specific processes triggered by the choice task. In order to clarify the source of the framing effect, we investigate the effect with different response modes: choice, rating, and ranking. The rating and ranking findings indicate that what is commonly called a risky choice framing effect is actually a framing effect that changes the evaluation of only the riskless option, although there is little or no effect on the risky option. According to these findings, risky choice framing might be construed as a process of attribute framing, which is independent of risk preference in choice contexts. Copyright © 2011 John Wiley & Sons, Ltd.     

Emotions within reason: Resolving conflicts in risk preference

This research focused on differential effects of emotional and rational preferences in decision making and how people resolve conflicting risk preferences caused by inconsistency between their emotional reactions to and rational assessment of a risk problem. In addition, effects of the framing of choice outcomes on emotional, rational, and overall risk preferences were examined. Adopting a within-subjects design, Study 1 showed that the emotional choice preference was often the opposite of the rational choice preference and was more risk-seeking than the rational preference. The overall favourability rating for a chosen option was significantly higher when the emotional choice and rational choice were the same than when they were opposed. Emotional preferences were significantly more susceptible than rational preferences to the hedonic tone of risky choice framing. The overall preference was a compromise of the conflicting emotional and rational preferences in some risk domains, and resembled either the emotional preference or the rational preference in other risk domains. Study 2, using a between-subjects manipulation, further confirmed that emotional preference and rational preference had differential effects on risky choice.     

Analysis of activity preferences as a function of differential consequences

Individuals who do not possess the verbal skills to express meaningful choice in the absence of its consequences may have difficulty indicating their preference for protracted activities that are unavailable until some time in the future (e.g., taking a walk, riding a bike). When we examined the preferences of 4 individuals with developmental disabilities by showing them pictorial representations of various activities, their initial choices showed no clear preferences. In a subsequent condition, selecting a photograph resulted in brief access to the depicted activity. When selections produced differential consequences (i.e., access to the activity), clear preferences emerged. In addition, 3 individuals' preferences were later shifted to an initially less preferred but more socially desirable option by superimposing additional reinforcement contingencies for engaging in the less preferred activity. Results are discussed in terms of the conditions under which choice functions as an indicator of preference and how those conditions may be altered to improve the quality of choice making without limiting access to preferred options.     

When mixed options are preferred in multiple‐trial decisions

We report three studies showing that in prospective multiple‐trial decisions people often select a mix of sure and risky options over pure bundles of either option. Such a preference is not ‘rational’ because a mixed option cannot be the EV‐maximizing choice. Experiment 1 confirmed a mixed‐option preference for gains but not for losses. Showing a graph of the multiple‐trial outcome distribution reduced but did not eliminate this effect, suggesting that it is not due purely to a failure to aggregate correctly over the multiple trials. Experiment 2 replicated the mixed option preference using a wider range of problems. Experiment 3 compared choices in the trinary choice conditions used in Experiments 1 and 2 with binary choices between pairs of the multiple‐trial sure, mixed, and risky options. In the binary choice condition the mixed option was no longer the modal choice, suggesting that the strong mixed option preference found in the trinary choice conditions is mainly due to a compromise effect. However, the binary choice probabilities did show violations of strong stochastic transitivity in a pattern that suggested a slight bias toward the mixed option. Copyright © 2006 John Wiley & Sons, Ltd.     

Behavioral and pharmacological variables affecting risky choice in rats.

The effects of manipulations of response requirement, intertrial interval (ITI), and psychoactive drugs (ethanol, phencyclidine, and d-amphetamine) on lever choice under concurrent fixed-ratio schedules were investigated in rats. Responding on the "certain' lever produced three 45-mg pellets, whereas responding on the "risky" lever produced either 15 pellets (p = .33) or no pellets (p .67). Rats earned all food during the session, which ended after 12 forced trials and 93 choice trials or 90 min, whichever occurred first. When the response requirement was increased from 1 to 16 and the ITI was 20 s, percentage of risky choice was inversely related to fixed-ratio value. When only a single response was required but the ITI was manipulated between 20 and 120 s (with maximum session duration held constant), percentage of risky choice was directly related to length of the ITI. The effects of the drugs were investigated first at an ITI of 20 s, when risky choice was low for most rats, and then at an ITI of 80 s, when risky choice was higher for most rats. Ethanol usually decreased risky choice. Phencyclidine did not usually affect risky choice when the ITI was 20 s but decreased it in half the rats when the ITI was 80 s. For d-amphetamine, the effects appeared to he related to baseline probability of risky choice; that is, low probabilities were increased and high probabilities were decreased. Although increase in risky choice as a function of the ITI is at variance with previous ITI data, it is consistent with foraging data showing that risk aversion decreases as food availability decreases. The pharmacological manipulations showed that drug effects on risky choice may be influenced by the baseline probability of risky choice, just as drug effects can be a function of baseline response rate.     

Reinforcement uncertainty enhances preference for choice in humans

Under concurrent‐chains schedules of reinforcement, participants often prefer situations that allow selection among alternatives (free choice) to situations that do not (forced choice). The present experiment examined the effects of reinforcement probability on choice preferences. Preferences for free versus forced choice were measured under a condition in which participants' choices were always reinforced (reinforcement probability of 1.0) and a condition in which outcomes were uncertain (reinforcement probability of 0.5). Forty‐four college students participated and preferences were examined under a concurrent‐chains schedule of reinforcement. Participants preferred free choice under uncertain reinforcement, but a bias toward free choice was not observed when reinforcement was certain. These results align with previous findings of preference for free choice under conditions of uncertainty, but suggest that preference may be dependent upon probabilistic reinforcement contingencies in the terminal links of the concurrent‐chains arrangement. Thus, reinforcement probability is an important variable to consider when conducting similar studies on the value of choice.     

Children's preference for mixed‐ versus fixed‐ratio schedules of reinforcement: A translational study of risky choice

Laboratory research has shown that when subjects are given a choice between fixed‐ratio and bi‐valued mixed‐ratio schedules of reinforcement, preference typically emerges for the mixed‐ratio schedule even with a larger ratio requirement. The current study sought to replicate and extend these findings to children's math problem completion. Using an ABCBC reversal design, four fourth‐grade students were given the choice of completing addition problems reinforced on either a fixed‐ratio 5 schedule or one of three mixed‐ratio schedules; an equivalent mixed‐ratio (1, 9) schedule, a mixed‐ratio (1, 11) schedule with a 20% larger ratio requirement, and an equally lean mixed‐ratio (5, 7) schedule without the small fixed‐ratio 1 component. This was followed by a reversal back to the preceding phase in which preference for the mixed‐ratio schedule had been observed, and a final reversal back to the mixed‐ratio (5, 7) phase. Findings were consistent with previous research in that all children preferred the mixed‐ratio (1, 9) schedule over the equivalent fixed‐ratio 5 schedule. Preference persisted for the leaner mixed‐ratio (1, 11) schedule for three of the four children. Indifference or preference for the fixed‐ratio 5 alternative was observed in phases containing the mixed‐ratio (5, 7) schedule. These results extend previous research on risky choice to children's math problem completion and highlight the importance of a small ratio component in the emergence of preference for bi‐valued mixed‐ratio schedules. Implications of these results for arranging reinforcement to increase children's academic responding are discussed.     

Choice between sequences of fixed-ratio schedules: effects of ratio values and probability of food delivery.

Pigeons were exposed to schedules of food delivery that consisted of two sequential fixed ratios. When alternative sequences provided two food deliveries per 50 responses, the schedule with the shorter initial fixed-ratio value was consistently preferred. Progressively reducing from 1.0 to .25 the probability of food delivery following completion of the second fixed ratio of the sequence with the shorter initial fixed ratio did not reduce preference for this sequence. Moreover, the sequence with the shorter initial fixed ratio also was preferred when the probability of food delivery following completion of the initial ratio in that sequence was progressively reduced from 1.0 to .5, although preference shifted to the alternative when the probability was reduced to 0. These findings suggest that the length of the initial fixed ratio was a primary determinant of choice. Subsequent manipulations demonstrated, however, that when the initial fixed ratios of the two alternatives were equal, changes in the ratio value and probability of food delivery following completion of the second fixed ratio lawfully affected choice.     

Exchange delays and impulsive choice in adult humans.

Choice responding by adult humans in a discrete-trial task was examined as a function of conditions that manipulated either the delay to point delivery or the delay between points and their exchange for money. In point-delay conditions, subjects chose between an "impulsive" alternative that provided a small amount of points immediately and a "self-control" alternative that provided a larger amount of points delayed by 15, 30, or 60 s. Points were exchanged for money immediately following the session. Subjects preferred the self-control alternative. In exchange-delay conditions, subjects chose between a small amount of points exchangeable for money immediately following the session and a larger amount of points exchangeable for money after 1 day, 3 weeks, or 6 weeks. A self-control preference observed for all subjects in the 1-day exchange-delay condition reversed to exclusive impulsive preference for 4 of the 6 subjects when choice conditions involved exchange delays of 3 or 6 weeks. These results show that human choice is sensitive to the manipulation of exchange delays and that impulsive preference can be obtained with exchange delays on the order of weeks.     

Effect propensity

In a choice between two options, decision makers can often be roughly divided into three groups: those who strongly prefer the first option, those who strongly prefer the second option, and those whose choices are most sensitive to the specific conditions (Switchers). In any reference state, such as the experimental control, Switchers’ choices are unlikely to be exactly equally divided between the options, which potentially creates a ceiling effect among those most susceptible to influence by the particular conditions or experimental manipulations. The limited growth potential of the option favored by Switchers in the reference state can produce “effect propensity,” whereby any condition or manipulation applied to the reference state is more likely to increase the share of the other option. We test this proposition in a series of studies in the context of choices between safe and risky options and between lower-price/quality and higher-price/quality options. The results indicate that a large majority of conceptually unrelated manipulations tend to increase the choice share of risky and higher-price/quality options. This effect propensity can be reversed when the risky and higher-price/quality options are the status quo alternatives or asymmetrically dominating in the reference state. Alternative explanations for effect propensity are examined. We discuss the implications of effect propensity for the interpretation of research findings, the selection of controls, and theory tests.     

内隐自尊和风险偏好对大学生职业决策的影响

为研究影响大学生职业决策的影响因素和决策有效性,实验一、二分别从决策者心理特征（内隐自尊与风险偏好）和职业方案特征（框架效应与风险水平）入手,考察二者对大学生职业决策行为的影响。结果发现：内隐自尊和风险偏好的高低显著影响大学生择业倾向性;大学生对风险水平不同的职业方案的选择倾向由低到高依次为冒险、折中、保守方案;职业决策存在明显的框架效应。研究表明,大多数大学生倾向于选择保守的职业方案;高风险偏好的大学生倾向于选择冒险的职业方案;高内隐自尊大学生倾向于主动择业;积极表述的职业方案更受大学生所青睐。     

Effects of valence and framing in decision making II: Estimating subjective weighting1

Abstract: In comparison between choice options, judgments of “How much better is a preferred option?” and “How much worse is a less preferred option?” may differ in their magnitudes. Such discrepancies are called “valence effects.” Previously, Yamagishi and Miyamoto (1996) observed systematic positive valence effects (“Better” exceeding “Worse”) in the domain of gains and systematic negative valence effects (“Worse” exceeding “Better”) in the domain of losses. The current experiment used the directions of valence effects as a tool to assess the decision maker's interpretation of choice tasks under the “framing effect” ( Tversky & Kahneman, 1986 ). Preferences under the framing effect switch from certain options in the domain of gains to uncertain options in the domain of losses. This study examined whether preferences for certain options were associated with positive valence effects, whereas preferences for uncertain options were associated with negative valence effects. Moreover, conditions under which preference reversals under the framing manipulations ceased to occur were examined. The effects of valence showed that framing effects ceased to occur when decision makers maintained consistent task interpretations as pertaining to gains or to losses. Most importantly, the pattern of subjective weighting under the valence effects was consistent with previous explanation of valence effects ( Yamagishi & Miyamoto, 1996 ). Possibilities for extending the current findings to understanding related psychological phenomena are discussed.