Food choice in the laboratory pigeon

Although food reward plays a large role in learning and behavioral experiments, there have been few studies examining the most motivating food reward for pigeons. Brown (1969) found that pigeons had a tendency to prefer peas, while Killeen et al. (1993) found pigeons to prefer peas and popcorn in Experiment 1A. We looked to further explore these options as well as expand upon the types of foods examined beyond mainly grains and seeds. Pigeons were presented with six novel foods (granulated peanuts, popping corn, freeze-dried mealworms, bread crumbs, split peas, and sunflower hearts) allocated into two sets of three food items. Once the most consumed food from each food set was determined, they were pooled together with sorghum seeds (a familiar food) to form a third set. Sunflower hearts were the most consumed of all the food items, followed by corn and granulated peanuts. We discuss the potential factors mediating consumption choice, including nutritional profile and food particle size.     

Reward context determines risky choice in pigeons and humans

Whereas humans are risk averse for monetary gains, other animals can be risk seeking for food rewards, especially when faced with variable delays or under significant deprivation. A key difference between these findings is that humans are often explicitly told about the risky options, whereas non-human animals must learn about them from their own experience. We tested pigeons (Columba livia) and humans in formally identical choice tasks where all outcomes were learned from experience. Both species were more risk seeking for larger rewards than for smaller ones. The data suggest that the largest and smallest rewards experienced are overweighted in risky choice. This observed bias towards extreme outcomes represents a key step towards a consilience of these two disparate literatures, identifying common features that drive risky choice across phyla.     

Preference for a segmented schedule using a brief S+ stimulus correlated with a great delay reduction in humans

Past studies using the concurrent-chain procedure showed that pigeons and humans generally prefer an unsegmented schedule to a segmented schedule. This finding is ostensibly inconsistent with theories of conditioned reinforcement such as delay-reduction theory. In the present study with humans, two changes in the basic segmented schedule were implemented to resolve this inconsistency. The first change was that in the segmented schedule the terminal-link stimulus (S+ stimulus) changed late in the terminal-link, close to reinforcement presentation. The second change was that the presentation of the segmenting stimulus, S+, was brief allowing a reinstatement of the early terminal-link stimulus, which is contiguous with reinforcement. Our data constitute the first demonstration of preference for the segmented schedule when a brief S+ is correlated with a greater reduction in delay to reinforcement.     

The choice behaviour of pigs in a Y maze: effects of deprivation of feed, social contact and bedding

We examined effects of deprivation of feed, social contact and bedding on the choice behaviour in Y maze tests. Eighty pigs were used to study two main effects: feed (estimated voluntary feed intake (VFI) vs. 70% VFI) and bedding (presence vs. absence), experiment 1; social contact (full vs. restricted) and bedding (presence vs. absence), experiment 2; and feed (as in experiment 1) and social contact (as in experiment 2), experiment 3.Overall pigs consistently chose feed and social contact over bedding. While social contact was more preferred than feed in experiment 3, there was substantial variation between pigs in their choice behaviour. The overall choice behaviour in experiment 3 contradicts previous research, but differences such as the preference methodology as well as the level of deprivation, level of reward and cost involved in accessing reward, may be responsible. Average daily weight gain (ADG) was affected in experiment 3: both feed and social restriction reduced ADG. While the feed effect is expected, one interpretation of the social effect is that social deprivation, through stress, may have reduced ADG. These results provide limited support for the notion that deprivation of a highly preferred resource may disrupt biological function.     

The matching law and effects of reinforcer rate and magnitude on choice in transition

Four pigeons responded in a concurrent-schedule procedure in which reinforcer rates and magnitudes changed unpredictably across sessions according to independent random series. Programmed relative reinforcement rates and magnitudes were always either 2:1 or 1:2. Pigeons' response allocation tended to stabilize within sessions and multiple regression analyses showed that it was determined by rates and magnitudes from the current session. Sensitivity coefficients were positive and statistically significant for current-session reinforcement and magnitude ratios. Although there were individual differences in sensitivity to rate and magnitude, their interaction was not significant across subjects. Rate and magnitude both controlled responding in single sessions and individual interreinforcer intervals. Analyses of responding within sessions showed that preference was more extreme when the richer rate and larger magnitude were associated with the same alternative than when they were associated with different alternatives. Overall, results support the concatenated generalized matching law's assumptions of additivity and independence as applied to choice in transition.     

Human choice among five alternatives when reinforcers decay

Human participants played a computer game in which choices among five alternatives were concurrently reinforced according to dependent random-ratio schedules. "Dependent" indicates that choices to any of the wedges activated the random-number generators governing reinforcers on all five alternatives. Two conditions were compared. In the hold condition, once scheduled, a reinforcer - worth a constant five points - remained available until it was collected. In the decay condition, point values decreased with intervening responses, i.e., rapid collection was differentially reinforced. Slopes of matching functions were higher in the decay than hold condition. However inter-subject variability was high in both conditions.     

模拟昆虫视觉-行为抉择的强化学习模型

视觉信息用于行为抉择的过程是一个极其复杂的脑信息处理过程,昆虫或动物对外界环境的学习是以价值来控制的,并可影响其行为抉择,研究这一过程对揭示人类自身脑运行机制有重要意义.文章在郭爱克研究小组果蝇实验提供的生物依据基础上,提出了一种模拟果蝇视觉-行为抉择的神经网络模型.该模型引入了价值和基于价值的强化学习算法,应用于输入视觉图像的强化学习,以此建立果蝇脑内多巴胺和蘑菇体对于抉择判断的价值体系.模拟的结果表明,该模型可以模拟果蝇视觉信息的学习和行为抉择过程,其结果与生物实验相符,同时也为机器人视觉信息控制行为抉择的应用提供了基础.     

Optimal risky choice in humans: effects of amount of variability

The present study investigated whether the predictions of an optimal risk-sensitive foraging model (the energy-budget rule) would extend to humans’ choices between high- and low-variance monetary response options. In Experiment 1, participants were presented with repeated choices between two options that had the same mean values but different variances across positive- and negative-budget conditions. In Experiment 2, a within-subject comparison was conducted to investigate choice under positive- and negative-budget conditions when the options were either (a) a fixed option and a high-variance option, or (b) a low-variance option and a high-variance option. Session-wide choices were analyzed in relation to the predictions of the energy-budget rule and sequential choices were analyzed with dynamic optimization modeling. When both options were variable choice was generally consistent with predictions of the energy-budget rule and was more risk prone under negative-budget than positive-budget conditions. Sequential choices were sensitive to local budget conditions, but choices were less consistent with optimality when both options were variable, possibly because of the greater similarity in expected earnings for optimal and nonoptimal choices in these conditions. Overall, the results provide further evidence that the energy-budget rule may have broad applicability and that it can extend to human risky choice between multiple variable response options.     

Discrete-trial vs. continuous free-operant procedures in assessing whether reinforcement context affects reinforcement value

Pigeons were trained to respond to two alternating concurrent reinforcement schedules. The reinforcement probabilities were .05 and .10 in one component, and .10 and .20 in the other. In one condition, the pigeons received training on a discrete-trial procedure in which the keylights remained illuminated for 5s or until a response occurred. In another condition, pigeons received training on a procedure in which the reinforcement contingencies were the same as in the discrete-trial procedure, but the stimuli were not turned off after 5s or after a response. Following training in each condition, probe tests were presented. In both conditions, the .20 alternative was, overall, preferred to the .05 alternative during probe tests. Following discrete-trial training, there was no reliable preference between the two .10 alternatives. However, when the stimuli remained illuminated during the intertrial interval periods during training, probe tests results showed preference for the .10 alternative that had been presented in the leaner context during training. The pattern of results is consistent with the notion that probe preference can be influenced both by the absolute reinforcement schedules associated with each alternative, as well as changeover behavior developed during training.     

Generic sustainability assessment themes and the role of context: The case of Danish maize for German biogas

The choice of context-generic or -specific themes and subthemes (goals and objectives) for sustainability assessment implies a number of tradeoffs; for instance, benchmarking and resource efficiency vs. coverage and engagement. Analyses of the potentials and limitations of generic assessment themes and sub-themes within specific contexts may help to develop frameworks that minimise the tradeoffs between generic and specific assessment approaches. The aim of this study was to analyse the effectiveness of generic themes and sub-themes of existing frameworks for covering the key sustainability issues of a specific case study – the case of Danish maize for German biogas. The results indicate that generic frameworks can effectively cover context-specific issues related to the environmental dimension of sustainability. Conversely, generic frameworks can be unable to identify context-specific issues related to social and economic dimensions. This study suggests that the coverage gap of generic themes is mainly an issue of framework incompleteness that can be advanced with additional research. A one-size-fits-all specificity-level for sustainability assessment is not applicable, and the specificity-level should be tailored to the assessment purpose. A certain degree of stakeholder participation is recommended not only in the assessment process, but also during the framework design to support stakeholders' sustainability education and action.     

The role of context, colour and location cues in socially learned novel food source preferences in starlings, Sternus vulgaris

Although the opportunity for errors in social learning is widely recognised, as yet little research has been directed towards understanding specific inaccuracies, biases and limitations in social learning and the mechanisms that give rise to them. In two experiments I ask how starlings, Sternus vulgaris, identify exemplars of novel feeders previously learned about socially. I find that starlings have a stronger response to feeders in the same context as that in which social learning took place, compared to identical and nonidentical feeders in a different context. Within a context that matches where social learning took place, starlings prefer feeders that show the same location and colour as the feeder demonstrated by the demonstrator starling, and show no preference when colour and location cues are dissociated. This suggests that starlings are relatively accurate social learners, since they show strong responses to novel foraging options only if they match the context, colour and location of options learned about socially, and they do so after very few trials. Furthermore, the responses of the subjects were compatible with conditioned learning-like mechanisms, which provide a useful basis for the further investigation of the origins and implications of errors in social learning.     

Reinforcement omission in concurrent fixed-interval and random-interval schedules

The present experiment examined overall and local effects of omission of reinforcers in a choice situation. Pigeons' key-pecking responses were reinforced under concurrent fixed-interval and random-interval schedules of food presentation. After some weeks of baseline sessions in which the probability of reinforcement was 1.00, approximately 25% of food presentations from the fixed-interval schedule were omitted and replaced by timeout periods. In such omission sessions, the overall relative rates of responding to the fixed-interval schedule became lower than those in the baseline sessions. On the other hand, when relative rates of responding to the fixed-interval schedule in the omission sessions were calculated separately for fixed-interval cycles preceded by timeout periods and those preceded by food presentations, the relative rates in the former type of fixed-interval cycles were higher than those in the latter type for three out of four pigeons. These results mean that relative rates of responding cannot always be regarded as reflecting a relative value of an alternative, and that the overall effect of the omission of fixed-interval reinforcers is not reducible to the local effect of omission.     

Energetic challenges unmask the role of ovarian hormones in orchestrating ingestive and sex behaviors

Effects of ovarian hormones on sex and ingestive behavior are well studied, and yet, their role in diverting attention from food to sex has not been examined directly, possibly because these functions are masked under conditions of excessive food abundance typical of the laboratory. Female Syrian hamsters were either fed ad libitum or food-restricted to 75% of their ad libitum intake for 8 days and then tested every day of the estrous cycle for their preference for males versus food, food hoarding and food intake in an apparatus designed to mimic aspects of their natural habitat. The food-restricted, but not the fed females, varied significantly over the estrous cycle in appetitive behaviors, which included their preference for males versus food and in the amount of food hoarded, with low food hoarding and high male preference on the night of ovulation. In contrast, there were no significant differences between restricted and ad libitum-fed females in the consummatory behaviors, namely, food intake or lordosis duration. In ovariectomized females, estradiol plus progesterone treatment delayed food restriction-stimulated hoarding and hastened feeding-inhibited hoarding without affecting food intake or lordosis duration. In summary, energy restriction and the presence of males unmasked an effect that was obscured in the normal laboratory conditions characterized by isolation and an over abundance of readily available food. These results are consistent with the idea that ovarian hormones orchestrate appetites for food and sex to optimize reproductive success under fluctuating energetic conditions.     

Resistance to change varies inversely with reinforcement context

We report two experiments which test whether resistance to prefeeding and satiation for a variable-interval (VI) schedule that delivers a constant rate of reinforcement varies inversely with the reinforcement rate for an alternative schedule. In Experiment 1, eight pigeons responded in a multiple schedule in which the red key was always associated with a VI 90-s schedule and the green key with either a richer (VI 18s) or leaner (VI 540s) schedule in different conditions. After baseline training in each condition, prefeeding test sessions were conducted in which 10g, 20g, 30g, 40g, and 50g food were provided one-hour prior to test. Additional baseline training was given between each test session. In Experiment 2, two groups of pigeons responded in a multiple schedule similar to Experiment 1. After baseline training, pigeons were exposed to a 5-h satiation test session in which the VI 90-s schedule was available continuously. Test sessions were conducted when pigeons were maintained at 85%, 95%, and 85% of their body weights in an ABA design. Results of both experiments showed that responding in the VI 90-s schedule that alternated with a leaner schedule during baseline was more resistant to prefeeding and satiation. These data rule out alternative explanations for results of previous studies, and confirm that resistance to change varies inversely with reinforcement context.     

Discounting the freedom to choose: implications for the paradox of choice

Organisms prefer to make their own choices. However, emerging research from behavioral decision making sciences has demonstrated that there are boundaries to the preference for choice. Specifically, many decision makers find an extensive array of choice options to be aversive, often leading to negative emotional states and poor behavioral outcomes. This study examined the degree to which human participants discounted hypothetical rewards that were (a) delayed, (b) probabilistic, and (c) chosen from a large array of options. The present results suggest that the "paradox of choice" effect may be explained within a discounting model for individual patterns of decision making.     

Non-verbal behavior as courtship signals: the role of control and choice in selecting partners

In this work, we provide evidence based on direct observation of behavior in encounters of opposite-sexed strangers, that women initiate and “control” the outcome. In the first minute of these videotaped 10-min interactions, neither female “solicitation” behavior nor “negative” behavior is strongly related to professed interest in the man, while female “affirmative” behavior at this stage modulates male verbal output in later stages (4–10 min). Although the rate of female courtship-like behavior is significantly higher in the first minute, it is only in the fourth to tenth minute that the rate of female courtship-like behavior is correlated with professed female interest. We hypothesize that this serves as a strategic dynamic reflecting sexual asymmetry in parental investment and the potential cost of male deception to women. Ambiguous protean behavioral strategies veil individuals' intentions and make their future actions unpredictable. These behavioral strategies may result in men's overestimation of female sexual interest.     

The value of constant surveillance in a risky environment

In risky environments, where threats are unpredictable and the quality of information about threats is variable, all individuals face two fundamental challenges: balancing vigilance against other activities, and determining when to respond to warning signals. The solution to both is to obtain continuous estimates of background risk, enabling vigilance to be concentrated during the riskiest periods and informing about the likely cost of ignoring warnings. Human surveillance organizations routinely produce such estimates, frequently derived from indirect cues. Here we show that vigilant individuals in an animal society (the pied babbler, Turdoides bicolor) perform a similar role. We ask (i) whether, in the absence of direct predator threats, pied babbler sentinels react to indirect information associated with increased risk and whether they communicate this information to group mates; (ii) whether group mates use this information to adjust their own vigilance, and whether this influences foraging success; and (iii) whether information provided by sentinels reduces the likelihood of inappropriate responses to alarm calls. Using playback experiments, we show that: (i) sentinels reacted to indirect predator cues (in the form of heterospecific alarm calls) by giving graded surveillance calls; (ii) foragers adjusted their vigilance in reaction to changes in surveillance calls, with substantial effects on foraging success; and (iii) foragers reduced their probability of responding to alarm calls when surveillance calls indicated lowered risk. These results demonstrate that identifying attacks as they occur is only part of vigilance: equally important is continuous surveillance providing information necessary for individuals to make decisions about their own vigilance and evasive action. Moreover, they suggest that a major benefit of group living is not only the increased likelihood of detecting threats, but a marked improvement in the quality of information available to each individual.     

Cyanide toxicity and interference with diet selection in quail (Coturnix coturnix)

Cyanide is a ubiquitous substance in the environment. Most of the cyanide absorbed by an animal is detoxified by enzymatic combination with sulfur, thus the detoxification process imposes a nutritional cost. In mammals, interactions among nutrients and toxics may influence the composition of the diet and food intake, as a function of positive or negative post-ingestive feedback. The present work aimed to describe the toxic effects of cyanide, and to determine whether cyanide interferes with diet selection in quail (Coturnix coturnix). A toxicological study was performed with 27 female quails that were assigned to three groups that received by gavage 0, 1.0 or 3.0 mg of KCN/kg/day, for 7 consecutive days. The diet selection trial was conducted with 20 female quails, that had access to two separate rations: a conventional quail ration and the same ration supplemented with 1% NaSO₄. During the toxicological study, clinical signs of poisoning and death occurred in a quail treated with cyanide. Histological changes were found only in animals dosed with cyanide, and these consisted of mild hepatic periportal vacuolation, an increased number of vacuoles in the colloid of the thyroid glands, and spongiosis in the mesencephalon. No clinical signs were found in any quail throughout the diet selection trial. There were no significant differences in food consumption or ration preference. In conclusion, exposure to cyanide promotes damage to the liver and central nervous system in quails. In contrast, the ingestion of sulfur by quail was not affected by exposure to cyanide.     

Modeling the dynamics of choice

A simple linear-operator model both describes and predicts the dynamics of choice that may underlie the matching relation. We measured inter-food choice within components of a schedule that presented seven different pairs of concurrent variable-interval schedules for 12 food deliveries each with no signals indicating which pair was in force. This measure of local choice was accurately described and predicted as obtained reinforcer sequences shifted it to favor one alternative or the other. The effect of a changeover delay was reflected in one parameter, the asymptote, whereas the effect of a difference in overall rate of food delivery was reflected in the other parameter, rate of approach to the asymptote. The model takes choice as a primary dependent variable, not derived by comparison between alternatives—an approach that agrees with the molar view of behaviour.