Limits to preference and the sensitivity of choice to rate and amount of food

Studies of choice holding food‐amount ratio constant while varying food‐rate ratio within sessions showed that local changes in preference depend on relative amount of food. The present study investigated whether sensitivity of choice to food‐rate ratio and sensitivity to food‐amount ratio are independent of one another when food‐rate ratios are varied across sessions and food‐amount ratios are varied within sessions. Food deliveries for rats’ presses on the left and right levers were scheduled according to three different food‐rate ratios of 1:1, 9:1, and 1:9; each food‐rate ratio lasted for 106 sessions and was arranged independently of seven food‐amount ratios (7:1, 6:2, 5:3, 4:4, 3:5, 2:6, and 1:7 food pellets) occurring within sessions in random sequence. Each amount ratio lasted for 10 food deliveries and was separated from another by a 60‐s blackout. Sensitivity to rate ratio was high (1.0) across food deliveries. Sensitivity to amount ratio was low when food rates were equal across alternatives, but was high when rate ratio and amount ratio opposed one another. When rate ratio and amount ratio went in the same direction, choice ratio reached an elevenfold limit which reduced sensitivity to approximately zero. We conclude that three factors affect sensitivity to amount: (1) the limit to preference, (2) the equal effect on preference of amounts greater than four pellets, and (3) the absence of differential effects of switches in amount in the equal‐rates (1:1) condition. Taken together, these findings indicate that rate and amount only sometimes combine independently as additive variables to determine preference when amount ratios vary frequently within sessions.     

Behavioral momentum theory fails to account for the effects of reinforcement rate on resurgence

The behavioral‐momentum model of resurgence predicts reinforcer rates within a resurgence preparation should have three effects on target behavior. First, higher reinforcer rates in baseline (Phase 1) produce more persistent target behavior during extinction plus alternative reinforcement. Second, higher rate alternative reinforcement during Phase 2 generates greater disruption of target responding during extinction. Finally, higher rates of either reinforcement source should produce greater responding when alternative reinforcement is suspended in Phase 3. Recent empirical reports have produced mixed results in terms of these predictions. Thus, the present experiment further examined reinforcer‐rate effects on persistence and resurgence. Rats pressed target levers for high‐rate or low‐rate variable‐interval food during Phase 1. In Phase 2, target‐lever pressing was extinguished, an alternative nose‐poke became available, and nose‐poking produced either high‐rate variable‐interval, low‐rate variable‐interval, or no (an extinction control) alternative reinforcement. Alternative reinforcement was suspended in Phase 3. For groups that received no alternative reinforcement, target‐lever pressing was less persistent following high‐rate than low‐rate Phase‐1 reinforcement. Target behavior was more persistent with low‐rate alternative reinforcement than with high‐rate alternative reinforcement or extinction alone. Finally, no differences in Phase‐3 responding were observed for groups that received either high‐rate or low‐rate alternative reinforcement, and resurgence occurred only following high‐rate alternative reinforcement. These findings are inconsistent with the momentum‐based model of resurgence. We conclude this model mischaracterizes the effects of reinforcer rates on persistence and resurgence of operant behavior.     

A single session of meditation reduces of physiological indices of anger in both experienced and novice meditators

The goal of the present study was to explore how anger reduction via a single session of meditation might be measured using psychophysiological methodologies. To achieve this, 15 novice meditators (Experiment 1) and 12 practiced meditators (Experiment 2) completed autobiographical anger inductions prior to, and following, meditation training while respiration rate, heart rate, and blood pressure were measured. Participants also reported subjective anger via a visual analog scale. At both stages, the experienced meditators’ physiological reaction to the anger induction reflected that of relaxation: slowed breathing and heart rate and decreased blood pressure. Naïve meditators exhibited physiological reactions that were consistent with anger during the pre-meditation stage, while after meditation training and a second anger induction they elicited physiological evidence of relaxation. The current results examining meditation training show that the naïve group’s physiological measures mimicked those of the experienced group following a single session of meditation training.     

Anxiety and motor performance: More evidence for the effectiveness of holistic process goals as a solution to the process goal paradox

ObjectivesRecent research has reported the benefits of using holistic rather than part process goals to avoid the negative effects associated with the conscious processing of task relevant information by skilled but anxious athletes. This experiment compared the efficacy of these two goal focus strategies in a neutral condition and a competitive condition in which cognitive state anxiety was elevated.DesignLaboratory-based experimental design using a mixed model with between (process goal groups) and within-subjects (neutral and competitive) conditions.MethodThirty male and female undergraduate students aged between 19 and 44 years of age completed 896 practice repetitions of a race car driving simulation using discovery learning. Participants were then placed in either a holistic or part process goal group using stratified random assignment. The practice phase was followed by neutral and competitive conditions, during which driving performance and psychophysiological measures were collected.ResultsAnalysis of variance of lap times and driving errors revealed that the holistic process goal group outperformed the part process goal group in the competition condition. Analysis of psychophysiological measures suggested that the performance of both process goal groups in the competitive condition was associated with the investment of compensatory effort.ConclusionsCompared to part process goals, holistic process goals confer performance benefits for skilled athletes who perform under competitive pressure.     

A preliminary study of the comfort of paced respiration

In order to obtain basal information about what type of externally paced respiration is comfortable, 25 male and 25 female undergraduate students were asked to practice self‐paced respiration. After a 1‐min rehearsal following instructions on comfortable self‐paced respiration, subjects carried out 2 min of self‐paced respiration and rated their level of comfort on a scale of 1–5. This was repeated (up to a maximum of seven times) until the subject recorded a high rating. Results indicated that self‐paced respiration was most comfortable, irrespective of sex, when a respiratory pattern was attained of half the respiratory rate and nearly twice the tidal volume of the trainee's resting condition. Although respiratory sinus arrhythmia and heart rate were indicative of a decrease in cardiac vagal activity and end‐tidal PCO₂ was suggestive of a reduction in anxiety, these effects were small. The results have implications for the utilization of externally paced respiration.     

Choice, time allocation, and response rate during stimulus generalization

Six pigeons were trained to discriminate between two noise intensities using a procedure that assessed choice, time allocation, and response rate simultaneously and independently. Responses on the left or right key (R1 or R2) were respectively correct in the presence of two different intensities, S1 and S2. After a correct response, reinforcement became available for pecks on the center key. Reinforcement density for R1¦S1 relative to R2¦S2 was varied across experimental conditions. Generalization tests followed extensive training at each condition. As a function of stimulus intensity, proportions of initial choices of R2, of time spent in R2-initiated components, and of center-key responses emitted in R2-initiated components all yielded sigmoidal gradients of similar slope, which shifted slightly in location when relative reinforcement density changed. Changeovers were maximal where initial choice proportions approximated 0.5. Gradients relating the absolute number of center-key responses to stimulus intensity were also roughly sigmoidal, but were more sensitive to changes in reinforcement density. Gradients of momentary response rate also depended on reinforcement density. During training, large but transitory shifts in choice responding occurred when reinforcement density changed, while differences in momentary response rate developed slowly, suggesting separate control of choice and response rate by the contingencies of reinforcement.     

Duration and rate of reinforcement as determinants of concurrent responding

The duration and frequency of food presentation were varied in concurrent variable-interval variable-interval schedules of reinforcement. In the first experiment, in which pigeons were exposed to a succession of eight different schedules, neither relative duration nor relative frequency of reinforcement had as great an effect on response distribution as they have when they are manipulated separately. These results supported those previously reported by Todorov (1973) and Schneider (1973). In a second experiment, each of seven pigeons was exposed to only one concurrent schedule in which the frequency and/or duration of reinforcement differed on the two keys. Under these conditions, each pigeon's relative rate of response closely matched the relative total access to food that each schedule provided. This result suggests that previous failures to obtain matching may be due to factors such as an insufficient length of exposure to each schedule or to the pigeons' repeated exposure to different concurrent schedules.     

Cue effectiveness in communicatively efficient discourse production

Recent years have seen a surge in accounts motivated by information theory that consider language production to be partially driven by a preference for communicative efficiency. Evidence from discourse production (i.e., production beyond the sentence level) has been argued to suggest that speakers distribute information across discourse so as to hold the conditional per-word entropy associated with each word constant, which would facilitate efficient information transfer (Genzel & Charniak, 2002). This hypothesis implies that the conditional (contextualized) probabilities of linguistic units affect speakers' preferences during production. Here, we extend this work in two ways. First, we explore how preceding cues are integrated into contextualized probabilities, a question which so far has received little to no attention. Specifically, we investigate how a cue's maximal informativity about upcoming words (the cue's effectiveness) decays as a function of the cue's recency. Based on properties of linguistic discourses as well as properties of human memory, we analytically derive a model of cue effectiveness decay and evaluate it against cross-linguistic data from 12 languages. Second, we relate the information theoretic accounts of discourse production to well-established mechanistic (activation-based) accounts: We relate contextualized probability distributions over words to their relative activation in a lexical network given preceding discourse.     

AGGRESSION AS POSITIVE REINFORCEMENT IN MICE UNDER VARIOUS RATIO‐ AND TIME‐BASED REINFORCEMENT SCHEDULES

There is evidence suggesting aggression may be a positive reinforcer in many species. However, only a few studies have examined the characteristics of aggression as a positive reinforcer in mice. Four types of reinforcement schedules were examined in the current experiment using male Swiss CFW albino mice in a resident—intruder model of aggression as a positive reinforcer. A nose poke response on an operant conditioning panel was reinforced under fixed‐ratio (FR 8), fixed‐interval (FI 5‐min), progressive ratio (PR 2), or differential reinforcement of low rate behavior reinforcement schedules (DRL 40‐s and DRL 80‐s). In the FR conditions, nose pokes were maintained by aggression and extinguished when the aggression contingency was removed. There were long postreinforcement pauses followed by bursts of responses with short interresponse times (IRTs). In the FI conditions, nose pokes were maintained by aggression, occurred more frequently as the interval elapsed, and extinguished when the contingency was removed. In the PR conditions, nose pokes were maintained by aggression, postreinforcement pauses increased as the ratio requirement increased, and responding was extinguished when the aggression contingency was removed. In the DRL conditions, the nose poke rate decreased, while the proportional distributions of IRTs and postreinforcement pauses shifted toward longer durations as the DRL interval increased. However, most responses occurred before the minimum IRT interval elapsed, suggesting weak temporal control of behavior. Overall, the findings suggest aggression can be a positive reinforcer for nose poke responses in mice on ratio‐ and time‐based reinforcement schedules.