Altruism, reciprocity, and probability: Examining relations through a discounting framework.

Probability and reciprocation have been implicated as key variables for understanding altruism and cooperation. Social discounting, which describes the decline in reward value as the recipient increases in social distance, has provided a framework through which to examine altruistic and cooperative choice. A previous study introduced reciprocal discounting as a way of studying perceived altruism from others (termed reciprocal altruism). But probability discounting has not yet been examined in relation to reciprocal discounting. In order to extend research on reciprocal discounting, the present study evaluated correlations between social, reciprocal, and probability discounting as well as relations between standard social distance (used in social discounting) and reciprocal social distance (the participant's perceived social distance placement on someone else's list) among 129 participants. Upon evaluation, the fit of median reciprocal discount rates to the hyperbolic form was replicated. A strong correlation between social and reciprocal discount rates and a moderate correlation between social and probability discount rates were found as well. Additionally, reciprocal and probability discount rates yielded moderate correlations while reciprocal and standard social distance analyses revealed more correspondence between reward values when persons were socially close (i.e., Person 1) or socially distant (i.e., Person 100). This study provides further evidence that reciprocation and probability likely impact altruistic choice while laying groundwork for further investigations into social distance.

Biological evolution and behavioral evolution: two approaches to altruism.

Altruism may be learned (behavioral evolution) in a way similar to that proposed in the target article for its biological evolution. Altruism (over social space) corresponds to self-control (over time). In both cases, one must learn to ignore the rewards to a particular (person or moment) and behave to maximize the rewards to a group (of people or moments).

Howard Rachlin: An extended scientist.

During the latter half of his career, Rachlin's work increasingly focused on integrating the study of temporal discounting and social cooperation-choices for an extended self. His notion of a self that is extended across time and social space is a useful framework within which to consider Rachlin's impact as a philosopher, scientist, and mentor over the course of his 56-year career in behavior science.

Commodity discounting: Obstacles and solutions.

Addictive behaviors involve patterns of impulsive choices. Discount functions are a useful means of describing the behavioral contingencies involved in those impulsive choices. Although monetary discounting tasks have proven useful, most impulsive behaviors of interest involve nonmonetary consequences. OBJECTIVE: Developing effective commodity discounting tasks is critical for assessing how delay (and other variables) influences choice with respect to meaningful real-world commodities (e.g., high-calorie foods, alcohol, opioids, and other drugs). METHOD: Identifying the obstacles specific to nonmonetary commodity discounting and evaluating solutions to those obstacles. RESULTS: Those obstacles include (1) real versus hypothetical commodities, (2) framing, (3) commodity indivisibility, (4) diminishing marginal utility, and (5) variations in economic context. CONCLUSIONS: Solutions are presented and evaluated for each of these five obstacles, including the following: (1) assessing relevant experiences and explicitly stipulating transportation and storage issues, (2) systematic analyses across various wordings and holding wording constant across commodities, (3) using an adjusting delay procedure with only whole commodities, (4) assessing value for different commodity amounts (without delay) and adopting quantitative models of discounting that include marginal utility, and (5) controlling for motivating operations, accounting for individual histories, and using closed economies. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The Evolution of Behavior Analysis: Toward a Replication Crisis?

The Open Science Collaboration (Science, 349(6251), 1-8, 2015) produced a massive failure to replicate previous research in psychology-what has been called a "replication crisis in psychology." An important question for behavior scientists is: To what extent is behavior science vulnerable to this type of massive replication failure? That question is addressed by considering the features of a traditional approach to behavior science. Behavior science in its infancy was a natural science, inductive, within-subject approach that encouraged both direct and systematic replication. Each of these features of behavior science increased its resistance to three factors identified as responsible for the alleged replication crisis: (1) failures to replicate procedures, (2) low-power designs, and (3) publication bias toward positive results. As behavior science has evolved, the features of the traditional approach have become less ubiquitous. And if the science continues to evolve as it has, it will likely become more vulnerable to a massive replication failure like that reported by the Open Science Collaboration (Science, 349(6251), 1-8, 2015).

The Effects of Obligatory and Preferential Frames on Delay Discounting.

Human decision making is partly determined by the verbal stimuli involved in a choice. Verbal stimuli that may be particularly relevant to human decision making are the words should and like, whereby should is presumably associated with what one ought to choose, and like is presumably associated with what one prefers to choose. The current study examined the potential effects of should and like on decisions in a monetary delay-discounting task. Eighty-three participants were recruited from Amazon's Mechanical Turk and were randomly assigned to a sequence of 2 conditions-should and like-in a repeated-measures experimental design. Based on condition assignment, the questions "Which should you choose?" and "Which would you like to choose?" appeared above each monetary option and its respective delay. Overall, participants demonstrated significantly lower levels of discounting in the should condition when compared to the like condition. However, this effect was much less consistent for participants exposed to the should condition prior to the like condition. The results of the current investigation indicate that the use of the words should and like constitutes separate classes of verbal stimuli that we refer to as obligatory and preferential frames. The effect of obligatory and preferential frames on delay discounting may be relevant to the prediction and control of decision making in social contexts.

Human risky choice: delay sensitivity depends on reinforcer type.

The present study was designed to help bridge the methodological gap between human and nonhuman animal research in delay-based risky choice. In Part 1, 4 adult human subjects made repeated choices between variable-time and fixed-time schedules of 30-s video clips. Both alternatives had equal mean delays of 15 s, 30 s, or 60 s. Three of 4 subjects strongly preferred the variable-delay alternative across all conditions. In Part 2, these 3 subjects were then provided pairwise choices between 2 variable-time schedules with different delay distributions. Subjects generally preferred the variable-delay distributions with a higher probability of short-reinforcer delays, consistent with accounts based on nonlinear discounting of delayed reinforcement. There was only weak correspondence between experimental results and verbal reports. The overall pattern of results is inconsistent with prior risky choice research with human subjects but is consistent with prior results with nonhuman subjects, suggesting that procedural differences may be a critical factor determining risk-sensitivity across species.

Altruism and anonymity: A behavioral analysis.

The effect of anonymity on altruism was examined in a social discounting task with hypothetical rewards. Social discounting - the rate at which increases in social distance decrease value to the participant - was compared across three groups. Participants in the Anonymous group were told that recipients would not know who they were. Participants in the Observed group were asked to imagine that each of their choices was being observed by the recipient. Participants in the Standard group were given no special instructions with respect to anonymity or identity. Social discounting was measured at each of 7 social distances ranging from first closest friend or relative to the 100th closest. Social discount rates for all three groups were well described by hyperbolic functions. Participants in the Observed group were willing to forgo more money for the benefit of others (were more altruistic) than were those in the other two groups. Although participants in the Anonymous group, with no prospect of reciprocation, were willing to forgo less money for the sake of others than were those in the Observed group, they did express willingness to forgo significant amounts. This is some evidence that individual altruistic acts cannot be explained wholly by the possibility of reciprocation.

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.

Shaping behavioral patterns.

Pigeons were rewarded for distributing eight pecks across two keys (L and R) in various patterns. The simplest pattern was at least one switch between the two keys (LR or RL) anywhere during the sequence; the next simplest was at least one instance of LLRR or RRLL anywhere during the sequence; the next was LLLRRR or RRRLLL; the most complex was LLLLRRRR or RRRRLLLL. Note that each more complex pattern contains the simpler ones within it. Initially, all patterns were reinforced but amount of reinforcement varied directly with complexity of pattern. The pigeons typically began the eight-peck sequence by pecking on their dispreferred key and then switched to their preferred key during the sequence. In subsequent conditions, simpler patterns were progressively unreinforced until finally only the most complex pattern (exactly four pecks on one key followed by exactly four pecks on the other) was reinforced. Three of the 4 pigeons tested maintained responding under this contingency; responding of the 4th pigeon extinguished. A second group of 4 pigeons was exposed immediately after training to extinction of all patterns except the most complex one. Three of the pigeons failed to maintain responding and the 4th maintained responding at a very low level. These results are evidence that response patterns can be shaped directly without building them up from a sequence of individually reinforced responses. The results may serve as a model of how self-controlled and altruistic behavior can arise through reinforcement.

Social discounting and the prisoner's dilemma game.

Altruistic behavior has been defined in economic terms as "…costly acts that confer economic benefits on other individuals" (Fehr & Fischbacher, 2003). In a prisoner's dilemma game, cooperation benefits the group but is costly to the individual (relative to defection), yet a significant number of players choose to cooperate. We propose that people do value rewards to others, albeit at a discounted rate (social discounting), in a manner similar to discounting of delayed rewards (delay discounting). Two experiments opposed the personal benefit from defection to the socially discounted benefit to others from cooperation. The benefit to others was determined from a social discount function relating the individual's subjective value of a reward to another person and the social distance between that individual and the other person. In Experiment 1, the cost of cooperating was held constant while its social benefit was varied in terms of the number of other players, each gaining a fixed, hypothetical amount of money. In Experiment 2, the cost of cooperating was again held constant while the social benefit of cooperating was varied by the hypothetical amount of money earned by a single other player. In both experiments, significantly more participants cooperated when the social benefit was higher.

Valuing rewards to others in a prisoner's dilemma game.

People value rewards to others but discount those rewards based on social distance; rewards to a socially closer person are valued more than identical rewards to a socially more distant person (Jones and Rachlin, 2006). The concept of social discounting can explain cooperation and defection in two-player prisoner's dilemma (PD) games (Axelrod, 1980). The contingencies of a PD game are such that in any single game cooperation is costly to each player herself but beneficial to the other player. From the viewpoint of each player, the costs of cooperation are fully realized, but the benefits of cooperation are discounted by the social distance to the other player. The present experiment measured cooperation and defection in two PD-game conditions with differing reward magnitudes. In one (the 1-2-3-4 condition), the cost of cooperation exceeded its socially discounted benefit, and players were predicted to defect; in the other (the 1-2-9-10 condition), the discounted benefit of cooperation exceeded its cost, and players were predicted to cooperate. Over the course of repeated trials defection increased with the 1-2-3-4 condition but not with the 1-2-9-10 condition. Moreover, participants who rated their partners as closer, relative to random classmates, cooperated at higher rates--consistent with social discounting.

Commitment and self-control in a prisoner's dilemma game.

Humans often make seemingly irrational choices in situations of conflict between a particular smaller-sooner reinforcer and a more abstract, temporally extended, but larger reinforcer. In two experiments, the extent to which the availability of commitment responses-self-imposed restrictions on future choices-might improve self-control in such situations was investigated. Participants played a prisoner's dilemma game against a computer that played a tit-for-tat strategy-cooperating after a participant cooperated, defecting after a participant defected. Defecting produced a small-immediate reinforcer (consisting of points convertible to gift cards) whereas cooperating increased the amount of subsequent reinforcers, yielding a greater overall reinforcer rate. Participants were normally free to cooperate or defect on each trial. Additionally, they could choose to make a commitment response that forced their choice for the ensuing five trials. For some participants, the commitment response forced cooperation; for others, it forced defection. Most participants, with either commitment response available, chose to commit repeatedly despite a minor point loss for doing so. After extended exposure to these contingencies, the commit-to-cooperate group cooperated significantly more than a control group (with no commitment available). The commit-to-defect group cooperated significantly less than the control group. When both commitment alternatives were simultaneously available-one for cooperation and one for defection-cooperation commitment was strongly preferred. In Experiment 2, the commitment alternative was removed at the end of the session; gains in cooperation, relative to the control group, were not sustained in the absence of the self-imposed behavioral scaffold.

The Temporal Dynamics of Cooperation.

Parties in real-world conflicts often attempt to punish each other's behavior. If this strategy fails to produce mutual cooperation, they may increase punishment magnitude. The present experiment investigated whether delay-reduction - potentially less harmful than magnitude increase - would generate mutual cooperation as interactions are repeated. Participants played a prisoner's dilemma game against a computer that played a tit-for-tat strategy, cooperating after a participant cooperated, defecting after a participant defected. For half of the participants, the delay between their choice and the computer's next choice was long relative to the delay between the computer's choice and their next choice. For the other half, long and short delays were reversed. The tit-for-tat contingency reinforces the other player's cooperation (by cooperating) and punishes the other player's defection (by defecting). Both rewards and punishers are discounted by delay. Consistent with delay discounting, participants cooperated more when the delay between their choice and the computer's cooperation (reward) or defection (punishment) was relatively short. These results suggest that, in real-world tit-for-tat conflicts, decreasing delay of reciprocation or retaliation may foster mutual cooperation as effectively as (or more effectively than) the more usual tactic of increasing magnitude of reciprocation or retaliation.

Nicotine and the behavioral mechanisms of intertemporal choice.

Nicotine has been found to produce dose-dependent increases in impulsive choice (preference for smaller, sooner reinforcers relative to larger, later reinforcers) in rats. Such increases could be produced by either of two behavioral mechanisms: (1) an increase in delay discounting (i.e., exacerbating the impact of differences in reinforcer delays) which would increase the value of a sooner reinforcer relative to a later one, or (2) a decrease in magnitude sensitivity (i.e., diminishing the impact of differences in reinforcer magnitudes) which would increase the value of a smaller reinforcer relative to a larger one. To isolate which of these two behavioral mechanisms was likely responsible for nicotine's effect on impulsive choice, we manipulated reinforcer delay and magnitude using a concurrent, variable interval (VI 30s, VI 30s) schedule of reinforcement with 2 groups of Long-Evans rats (n=6 per group). For one group, choices were made between a 1-s delay and a 9-s delay to 2 food pellets. For a second group, choices were made between 1 pellet and 3 pellets. Nicotine (vehicle, 0.03, 0.1, 0.3, 0.56 and 0.74 mg/kg) produced dose-dependent decreases in preference for large versus small magnitude reinforcers and had no consistent effect on preference for short versus long delays. This suggests that nicotine decreases sensitivity to reinforcer magnitude.

Real and hypothetical rewards.

Laboratory studies of choice and decision making among real monetary rewards typically use smaller real rewards than those common in real life. When laboratory rewards are large, they are almost always hypothetical. In applying laboratory results meaningfully to real-life situations, it is important to know the extent to which choices among hypothetical rewards correspond to choices among real rewards and whether variation of the magnitude of hypothetical rewards affects behavior in meaningful ways. The present study compared real and hypothetical monetary rewards in two experiments. In Experiment 1, participants played a temporal discounting game that incorporates the logic of a repeated prisoner's-dilemma (PD) type game versus tit-for-tat; choice of one alternative ("defection" in PD terminology) resulted in a small-immediate reward; choice of the other alternative ("cooperation" in PD terminology) resulted in a larger reward delayed until the following trial. The larger-delayed reward was greater for half of the groups than for the other half. Rewards also differed in type across groups: multiples of real nickels, hypothetical nickels or hypothetical hundred-dollar bills. All groups significantly increased choice of the larger delayed reward over the 40 trials of the experiment. Over the last 10 trials, cooperation was significantly higher when the difference between larger and smaller hypothetical rewards was greater. Reward type (real or hypothetical) made no significant difference in cooperation. In Experiment 2, real and hypothetical rewards were compared in social discounting - the decrease in value to the giver of a reward as social distance increases to the receiver of the reward. Social discount rates were well described by a hyperbolic function. Discounting rates for real and hypothetical rewards did not significantly differ. These results add to the evidence that results of experiments with hypothetical rewards validly apply in everyday life.

Rate, probability and matching: comments on "The identities hidden in the matching laws, and their uses" by David Thorne.

David Thorne's (2010) article, "The identities hidden in the matching laws, and their uses" performs a valuable service in pointing out alternative expressions of matching. However, some identities tend to obscure rather than illuminate empirical relationships. Three such problematic instances are discussed: interresponse time as a function of interval and ratio schedule parameters; probability equality as implying rate matching; the apparent simplicity of probabilistic functions, as opposed to response rate functions, of reinforcement rate.

Isolating behavioral mechanisms of intertemporal choice: nicotine effects on delay discounting and amount sensitivity.

Many drugs of abuse produce changes in impulsive choice, that is, choice for a smaller-sooner reinforcer over a larger-later reinforcer. Because the alternatives differ in both delay and amount, it is not clear whether these drug effects are due to the differences in reinforcer delay or amount. To isolate the effects of delay, we used a titrating delay procedure. In phase 1, 9 rats made discrete choices between variable delays (1 or 19 s, equal probability of each) and a delay to a single food pellet. The computer titrated the delay to a single food pellet until the rats were indifferent between the two options. This indifference delay was used as the starting value for the titrating delay for all future sessions. We next evaluated the acute effects of nicotine (subcutaneous 1.0, 0.3, 0.1, and 0.03 mg/kg) on choice. If nicotine increases delay discounting, it should have increased preference for the variable delay. Instead, nicotine had very little effect on choice. In a second phase, the titrated delay alternative produced three food pellets instead of one, which was again produced by the variable delay (1 s or 19 s) alternative. Under this procedure, nicotine increased preference for the one pellet alternative. Nicotine-induced changes in impulsive choice are therefore likely due to differences in reinforcer amount rather than differences in reinforcer delay. In addition, it may be necessary to include an amount sensitivity parameter in any mathematical model of choice when the alternatives differ in reinforcer amount.