Experimental evidence for route integration and strategic planning in wild capuchin monkeys

Both in captivity and the wild, primates are found to travel mostly to the nearest available resource, but they may skip over the closest resource and travel to more distant resources, which are often found to be more productive. This study examines the tradeoff between distance and reward in the foraging choices of one group of wild capuchin monkeys (Cebus apella nigritus) using feeding platforms in large-scale foraging experiments conducted over four years. Three feeding sites were arrayed in an oblique triangle, such that once the monkey group had chosen one site to feed, they had a choice between two remaining sites, a close one with less food and the other up to 2.3 times as far away but with more food. Sites were provisioned once per day. The capuchins generally chose the closer feeding site, even when the more distant site offered up to 12 times as much food. The distances to, rewards of, or various profitability measures applied to each alternative site individually did not explain the group’s choices in ways consistent with foraging theory or principles of operant psychology. The group’s site choices were predicted only by comparing efficiency measures of entire foraging pathways: (1) direct travel to the more rewarding distant site, versus (2) the longer ‘detour’ through the closer site on the way to the more distant one. The group chose the detour more often when the reward was larger and the added detour distance shorter. They appeared to be more sensitive to the absolute increase in detour distance than to the relative increase compared to the straight route. The qualitative and quantitative results agree with a simple rule: do not use the detour unless the energy gain from extra food outweighs the energy cost of extra travel. These results suggest that members of this group integrate information on spatial location, reward, and perhaps potential food competition in their choice of multi-site foraging routes, with important implications for social foraging. This contribution is part of the special issue “ A Socioecological Perspective on Primate Cognition” (Cunningham and Janson 2007b).     

Pigeons' choices in situations of diminishing returns: fixed- versus progressive-ratio schedules.

In two different discrete-trial procedures, pigeons were faced with choices between fixed-ratio and progressive-ratio schedules. The latter schedules entail diminishing returns, a feature analogous to foraging situations in the wild. In the first condition (no reset), subjects chose between a progressive-ratio schedule that increased in increments of 20 throughout a session and a fixed-ratio schedule that was constant across blocks of sessions. The size of the fixed ratio was varied parametrically through an ascending and then a descending series. In the reset condition, the same fixed-ratio values were used, but each selection (and completion) of the fixed ratio reset the progressive-ratio schedule back to its minimal value. In the no-reset procedure, the pigeons tended to cease selecting the progressive ratio when it equaled or slightly exceeded the fixed-ratio value, whereas in reset, they chose the fixed ratio well in advance of that equality point. These results indicate sensitivity to molar as well as to molecular reinforcement rates, and those molar relationships are similar to predictions based on the marginal value theorem of optimal foraging theory (e.g., Charnov, 1976). However, although previous results with monkeys (Hineline & Sodetz, 1987) appeared to minimize responses per reinforcement, the present results corresponded more closely to predictions based on sums-of-reciprocals of distance from point of choice to each of the next four reinforcers. Results obtained by Hodos and Trumbule (1967) with chimpanzees in a similar procedure were intermediate between these two relationships. Variability of choices, as well as median choice points, differed between the reset and no-reset conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Improving postswitch performance in the dimensional change card-sorting task: the importance of the switch and of pretraining by redescribing the test cards

The dimensional change card-sorting task (DCCS) is used to assess the executive abilities of young children. Typically, 3-year-olds have difficulty in performing this task. However, the exact nature of this difficulty is still being debated. In the standard DCCS, children need to sort, for example, test cards with a blue flower or a red car into two boxes marked with the target cards. The 3-year-olds commonly have pronounced difficulty in switching from one sorting criterion (e.g., color) to another (e.g., shape). Here two experiments with 3-year-olds showed that making the transition between the sorting criteria more distinct improved performance significantly. This was achieved by taking away the target cards for a brief time period, asking a question irrelevant to the task, and pretraining the children by redescribing the test cards.     

The use of multiple reference points in risky decision making

Among psychologists and economists, prospect theory continues to be one of the most popular models of decision making. The theory's key property is reference dependence; specifically, how an individual's perception of loss or gain is dependent upon their starting point (i.e., the status quo). Although prospect theory is widely accepted, other authors have sought the inclusion of reference points besides the status quo. Initially these extensions focused on the importance of single reference points such as goals. More recently, authors have explained choice data by including multiple reference points within the value function. Multiple‐reference‐point theories generally assume that many choice situations possess an implicit or explicit goal, or point an individual will strive to obtain, and/or a minimum requirement (i.e., a “lower bound”) above which an individual will strive to stay. In two experiments, we present evidence that individuals can utilize the minimum requirement, status quo, and goal within a single risky decision task. Participants most often chose to maximize their chance of reaching reference points even when that decision was riskier, resulted in lower expected value, resulted in lower expected utility, or ran contrary to the predictions of prospect theory. Furthermore, salience and uncertainty moderated the use of goals and minimum requirements as reference points. Copyright © 2010 John Wiley & Sons, Ltd.     

GROUP FORAGING SENSITIVITY TO PREDICTABLE AND UNPREDICTABLE CHANGES IN FOOD DISTRIBUTION: PAST EXPERIENCE OR PRESENT CIRCUMSTANCES?

The ideal free distribution theory (Fretwell & Lucas, 1970) predicts that the ratio of foragers at two patches will equal the ratio of food resources obtained at the two patches. The theory assumes that foragers have "perfect knowledge" of patch profitability and that patch choice maximizes fitness. How foragers assess patch profitability has been debated extensively. One assessment strategy may be the use of past experience with a patch. Under stable environmental conditions, this strategy enhances fitness. However, in a highly unpredictable environment, past experience may provide inaccurate information about current conditions. Thus, in a nonstable environment, a strategy that allows rapid adjustment to present circumstances may be more beneficial. Evidence for this type of strategy has been found in individual choice. In the present experiments, a flock of pigeons foraged at two patches for food items and demonstrated results similar to those found in individual choice. Experiment 1 utilized predictable and unpredictable sequences of resource ratios presented across days or within a single session. Current foraging decisions depended on past experience, but that dependence diminished when the current foraging environment became more unpredictable. Experiment 2 repeated Experiment I with a different flock of pigeons under more controlled circumstances in an indoor coop and produced similar results.     

Transitive responding in hooded crows requires linearly ordered stimuli

Eight crows were taught to discriminate overlapping pairs of visual stimuli (A+ B-, B+ C-, C+ D-, and D+ E-). For 4 birds, the stimuli were colored cards with a circle of the same color on the reverse side whose diameter decreased from A to E (ordered feedback group). These circles were made available for comparison to potentially help the crows order the stimuli along a physical dimension. For the other 4 birds, the circles corresponding to the colored cards had the same diameter (constant feedback group). In later testing, a novel choice pair (BD) was presented. Reinforcement history involving stimuli B and D was controlled so that the reinforcement/nonreinforcement ratios for the latter would be greater than for the former. If, during the BD test, the crows chose between stimuli according to these reinforcement/nonreinforcement ratios, then they should prefer D; if they chose according to the diameter of the feedback stimuli, then they should prefer B. In the ordered feedback group, the crows strongly preferred B over D; in the constant feedback group, the crows' choice did not differ significantly from chance. These results, plus simulations using associative models, suggest that the orderability of the postchoice feedback stimuli is important for crows' transitive responding.     

Disentangling dimensions in the dimensional change card-sorting task

The dimensional change card-sorting task (DCCS task) is frequently used to assess young children's executive abilities. However, the source of children's difficulty with this task is still under debate. In the standard DCCS task, children have to sort, for example, test cards with a red cherry or a blue banana into two boxes marked with target cards showing a blue cherry and a red banana. Typically, 3-year-olds have severe problems switching from sorting by one dimension (e.g. color) to sorting by the other dimension (e.g. shape). Three experiments with 3- to 4-year-olds showed that separating the two dimensions as properties of a single object, and having them characterize two different objects (e.g. by displaying an outline of a cherry next to a red filled circle on the card) improves performance considerably. Results are discussed in relation to a number of alternative explanations for 3-year-olds' difficulty with the DCCS task.     

Differences, not ratios, control choice in an experimental analogue to foraging

In choice between outcomes with different delays to reinforcement, most theories require that choice be governed by the ratio of the delays, not by the difference between them, a requirement also consistent with Weber's law. Instead, delay-reduction theory and optimal-foraging theory stipulate, under conditions of the present experiments, that the difference between the delays, and not the ratio between them, controls choice. This prediction was assessed using a procedure, widely used in foraging experiments, in which pigeons chose between accepting and rejecting either of two delays when offered. Across conditions, the delays either differed by a constant amount, with the ratio between the delays varying, or differed by changing amounts, with the ratio between the delays constant. In each of six experiments, rate of acceptance of the longer delay depended only on the difference between the two delays and not on the ratio between them, supporting delay-reduction and foraging theory.     

奖惩对注意缺陷多动障碍儿童情感决策的影响

采用简化版儿童赌博任务,其中操纵了奖励和惩罚的强度,探察两种亚型（注意缺陷型和混合型）ADHD儿童的情感决策能力,同时采集儿童在任务中的皮肤电活动以探析ADHD儿童在情感决策中的生理机制。结果发现,在不同的奖惩强度下,ADHD儿童情感决策模式不同,在即刻奖励条件下,ADHD儿童情感决策的能力明显弱于正常对照组儿童,倾向于不利选择,所产生的预测性皮电振幅也明显低于正常对照组;在即刻惩罚条件下,ADHD儿童的情感决策能力未见异常。两种亚型ADHD儿童的表现模式相似。上述结果证明,ADHD儿童仅存在对奖励的异常敏感性,并确实影响了其决策能力,而其回避惩罚的能力正常。两种亚型ADHD儿童存在的问题相似     

选择一致性影响结果评价的ERP研究

本研究通过两个实验探讨了当被试主动做出与他人一致/不一致的选择行为(实验1)或看到他人做出与自己一致/不一致的选择行为(实验2)时,其选择行为的一致性是如何影响结果评价过程的。脑电数据表明在结果评价的早期阶段,无论被试是主动或被动地与他人做出相同选择,这种选择一致性都会放大输赢结果之间的差异:体现在选择一致情况下比不一致情况下诱发更大的d FRN。而在结果评价的晚期阶段,当被试先做出选择之后,看到他人做出与自己不一致的选择时(实验2),相比他人与自己选择一致时,诱发了更大的P3和LPP波幅。说明被试很可能把他人的不一致选择加工为一种冲突。因此投入了更多认知资源来加工这一结果。本研究是一个探索性的创新研究,首次从时间维度上分离了选择行为和结果反馈两个阶段,并提供了选择一致性对结果评价有影响作用的脑电证据。     

Effects of laterality and visual angle on time judgments: a phenomenological investigation of time durations

20 students from an undergraduate class participated in an experiment designed to study the effects of laterality and visual angle on time judgments. Using a standard two-field tachistoscope , subjects were exposed to two experimental conditions, (1) stimulus cards with a single red or blue dot in the center and several dots clustered on both sides near the center and equidistant from it (visual angle of .6 degrees) and (2) stimulus cards with a single red or blue dot in the center and several dots clustered on both sides away from the center on the edge of the card (visual angle of 2.6 degrees). Five cards containing a single red or blue dot were used to control for response bias. The subjects were asked to indicate whether they saw dots in the left, right, or both fields, and whether they perceived a time duration between fields. No difference in time duration existed, however, as all cards were exposed to both fields for equal durations. The predictions that the judged duration of dot patterns would be more accurate favoring the left visual-field and more accurate where the distance between the point of fixation and stimulus was larger were supported.     

Red and romantic behavior in men viewing women

In many non‐human primate species, a display of red by a female increases attraction behavior in male conspecifics. In two experiments, we investigate an analogous effect in humans, specifically, whether red on a woman's shirt increases attraction behavior in men. In Experiment 1, men who viewed an ostensible conversation partner in a red versus a green shirt chose to ask her more intimate questions. In Experiment 2, men who viewed an ostensible interaction partner in a red versus a blue shirt chose to sit closer to her. These effects were observed across participants' perceptions of their own attractiveness (Experiment 1) and general activation and mood (Experiment 2). Our findings suggest that red acts as a basic, non‐lexical prime, influencing reproduction‐relevant behavior in like manner across species. Copyright © 2010 John Wiley & Sons, Ltd.     

Isolated teenagers, cooperative learning, and the training of social skills

The effects of individual and group contingencies on the achievement and social integration of isolated, learning-disabled students were studied. Five socially isolated and withdrawn eighth-grade students in foreign-language and math classes were subjects. The choice of working alone or in a group with no academic contingency (i.e., bonus points) was compared with working in cooperative learning groups with a group-academic contingency (i.e., bonus points), a group-academic contingency with social-skills training, and a group-academic contingency in combination with a social-skills contingency (i.e., bonus points). The results indicated that the combination of group-academic and social-skills contingencies produced in the socially isolated and withdrawn students the highest rates of appropriate social interaction with peers, acceptance and liking by peers, positive attitudes toward the subject area, and achievement.     

Income and choice between different goods

In Experiment 1, 3 rats chose between two simultaneously operating variable-interval schedules, one of which provided saccharin water and the other, food. In five conditions, the absolute (and equal) reinforcement rates provided by the pair of equal-valued schedules were manipulated in the range of 36 to 240 per hour. Experiment 2 was identical to Experiment 1 except that these schedules operated successively, arranged by requiring the rat to stand on the side of the chamber correlated with each schedule. Food/saccharin choice ratios were inversely related to reinforcement rate in both experiments, although this effect was stronger in Experiment 2. When delivery rates were high, preference for food over saccharin often reversed as the session progressed. The results were interpretable in terms of economic accounts of choice (e.g., the minimum-needs hypothesis), as well as in terms of traditional psychological accounts (e.g., matching theory).     

金钱概念对消费者独特性需求的影响研究

本研究探讨了金钱概念对消费者独特性需求的影响。通过三个实验,实验1研究表明启动金钱概念的消费者在进行产品选择时反从众需求更强烈;实验2研究表明金钱的丰富程度会调节金钱概念对消费者创新性选择的影响,金钱富有启动组选择独特性产品的比例要显著高于金钱缺乏启动组和控制组;实验3研究表明金钱概念对消费者独特性需求的影响是通过社交距离的中介作用完成的,启动金钱概念的消费者会感知到更远的社交距离,进而产生更强烈的独特性需求。     

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.     

Integrating information about location and value of resources by white-faced saki monkeys (<Emphasis Type="Italic">Pithecia pithecia</Emphasis>)

Most studies of spatial memory in primates focus on species that inhabit large home ranges and have dispersed, patchy resources. Researchers assume that primates use memory to minimize distances traveled between resources. We investigated the use of spatial memory in a group of six white-faced sakis (Pithecia pithecia) on 12.8-ha Round Island, Guri Lake, Venezuela during a period of fruit abundance. The sakis’ movements were analyzed with logistic regressions, a predictive computer model and a computer model that simulates movements. We considered all the resources available to the sakis and compared observed distances to predicted distances from a computer model for foragers who know nothing about the location of resources. Surprisingly, the observed distances were four times greater than the predicted distances, suggesting that the sakis passed by a majority of the available fruit trees without feeding. The odds of visiting a food tree, however, were significantly increased if the tree had been visited in the previous 3 days and had more than 100 fruit. The sakis’ preferred resources were highly productive fruit trees, Capparis trees, and trees with water holes. They traveled efficiently to these sites. The sakis choice of feeding sites indicate that they combined knowledge acquired by repeatedly traveling through their home range with ‘what’ and ‘where’ information gained from individual visits to resources. Although the sakis’ foraging choices increased the distance they traveled overall, choosing more valued sites allowed the group to minimize intragroup feeding competition, maintain intergroup dominance over important resources, and monitor the state of resources throughout their home range. The sakis’ foraging decisions appear to have used spatial memory, elements of episodic-like memory and social and nutritional considerations. This contribution is part of the Special Issue “A Socioecological Perspective on Primate Cognition” (Cunningham and Janson 2007).     

Beliefs in a Just World and Reactions to Personal Deprivation

ABSTRACT We hypothesized that strong believers in a just world would be motivated to perceive personal deprivation as fair and to report little resentment, compared to weak believers in a just world In two experiments, subjects performed a computer task to earn points toward a goal that had desirable consequences In the first study, some subjects chose their computer task, whereas other subjects were randomly assigned to a task In the second study, some subjects decided not to practice the task before the test trial, whereas other subjects learned after the test trial that the experimenter had forgotten to give them the opportunity to practice All subjects received bogus feedback indicating that they did not earn any points The predicted relation between beliefs in a just world and perceived fairness was obtained in both experiments, especially within the choice condition of Experiments and the experimenter error condition of Experiments The results show that beliefs in a just world have implications not only for perceptions of others, but also for self-perception     

Free classification: Element-level and subgroup-level similarity

Subjects classified sets of multidimensional stimuli into two groups in any way they wished. The sets were composed of 6 or 12 stimuli: 2 or 4 instances of 3 different stimuli (e.g., 2 blue circles, 2 green circles, 2 red circles). There were striking individual differences in the preferred classification. Some subjects maximized the similarity between subgroups by matching the composition of the subgroups--one instance of each stimulus was placed in each group. The other subjects maximized the similarity among stimuli within each subgroup by placing similar stimuli in each group (the blues and greens in one group, the reds in the other). The nature of the stimuli as well as the relationships among the three stimuli had little effect on classification. In this case, cognitive styles specific to individuals but general across diverse dimensions and stimulus sets determined classification.     

Chunking versus foraging search patterns by rats in the hierarchically baited radial maze

Rats were exposed to a radial maze containing six black smooth arms and six wire-grid-covered arms and a striped 'exit arm' in experiment 1. The probability of a black or grid arm being baited (5/6 vs 1/6) with sunflower seeds was associated with its proximal cue for some rats (the Relevant Arm Cue group) but not for others (the Irrelevant Arm Cue group). All rats could terminate a trial and receive a highly preferred morsel of apple by entering the exit arm only after having sampled all six seed-baited arms. Relevant Arm Cue rats usually chose some arms from the more densely baited set before choosing an arm from the less densely baited set and made fewer reentries than Irrelevant Arm Cue rats. Although such clustered, higher choice accuracy in the Relevant Arm Cue group corresponds to human clustered, better recall of verbal items from lists hierarchically organized by categories, these rats did not similarly exhaustively retrieve items (arm locations). That is, when required to terminate a trial by entering the 'exit' arm for an apple morsel after having sampled all seed-baited arms, both groups were equally unable to withhold making nonrewarded premature exits. This nonexhaustive foraging search pattern was maintained in the next two experiments in which the radial maze was reduced to three black and three grid arms along with the striped 'exit' arm and in which black and grid arm cues were paired with number of seeds (eight or one) in an arm for Relevant Arm Cue rats. Although Relevant Arm Cue rats displayed perfect clustering by entering all eight-seeded arms before a one-seeded arm, they made more premature exits and reentries into eight-seeded arms in experiment 2 or when forced to enter all eight-seeded arms in experiment 3 than did Irrelevant Arm Cue rats. These foraging tendencies prevent accurate estimations of the amount of information (i.e., arm locations) rats can 'chunk'. Electronic Publication