Session duration and the VI response function: Within-session prospective and retrospective effects

Two experiments examined the effects of session duration on responding during simple variable-interval schedules. In Experiment 1, rats were exposed to a series of simple variable-interval schedules differing in both session duration (10 min or 30 min) and scheduled reinforcement rate (7.5 s, 15 s, 30 s, and 480 s). The functions relating response rate to reinforcement rate were predominantly monotonic for the short (10-min) sessions but were predominantly bitonic for the long (30-min) sessions, when data from the entire session were considered. Examination of responding within sessions suggested that differences in the whole-session data were produced by a combination of prospective processes (i.e., processes based on events scheduled to occur later in the session) and retrospective processes (i.e., processes based on events that had already occurred in the session). In Experiment 2, rats were exposed to a modified discrimination procedure in which pellet flavor (standard or banana) predicted session duration (10 min or 30 min). All rats came to respond faster during the short (10-min) sessions than during the first 10 min of the long sessions. As in Experiment 1, the results seemed to reflect the simultaneous operation of both prospective and retrospective processes. The results shed light on the recent controversy over the form of the variable-interval response function by identifying one variable (session duration) and two types of processes (prospective and retrospective) that influence responding on these schedules.     

儿童版特里尔社会应激测试对儿童唾液皮质醇、唾液α-淀粉酶和情绪的影响

研究以150名五、六年级的学生为被试,考察儿童版特里尔社会应激测试（TSST-C）对儿童客观生理反应（唾液皮质醇和唾液α-淀粉酶）和主观情绪反应的影响。结果发现,TSST-C引起了儿童显著的应激反应,包括皮质醇和唾液α-淀粉酶水平的升高,以及主观消极情绪（如焦虑和紧张）的增加,这表明TSST-C在中国儿童中的适用情况良好,能够有效诱发儿童的应激反应。同时,研究也发现,皮质醇反应和唾液α-淀粉酶反应不存在相关,生理反应和情绪反应之间也不存在相关。     

Skin temperature biofeedback for multiple sessions with monetary incentives

This study evaluated the relative effectiveness of two incentive contingencies in learning biofeedback-assisted control of peripheral skin temperature: positive versus positive/negative monetary incentives. Both incentive groups of 10 participated in six sessions, including pre- and posttraining voluntary control sessions, and four intervening sessions with visual feedback and monetary contingencies. Each session consisted of adaptation, resting baseline, feedback or voluntary control, and a final resting baseline. The results indicated no significant difference in response control between groups and an over-all decline in temperature within sessions. Self-control was evidenced by the slower rate of decline in temperature for the first as compared to the last session, and feedback control by the attenuation in the rate of decline in the last three training sessions. Based on data from other physiological responses, these findings are not likely due to habituation effects. It was concluded that response control should not necessarily be defined in terms of increasing temperature but rather by reference to an appropriate comparison condition. Motivational effects should be further investigated with alternative incentive contingencies.     

The Conundrum of the Laboratory: Challenges of Assessing Preschool-Age Children’s Salivary Cortisol Reactivity

The laboratory assessment of young children’s cortisol reactivity is a major obstacle in psychoneuroendocrine research. The current study aimed to test the effectiveness of a developmentally-appropriate stressor paradigm in the laboratory with a sample of 152 preschool-age children. Salivary cortisol samples were obtained at 30 min after arrival to the laboratory and at 20, 30, 40, and 50 min post-stressor. Observations of children’s positive emotions (PE) and negative emotions (NE) were coded to assess children’s behavioral response to the paradigm. Children’s mean growth curve evidenced a significant linear decrease in cortisol values from baseline to 20 min post-stress and a leveling off by 40 min post-stress. However, when taking into account children’s individual differences in the timing of peak cortisol response, we observed a significant increase in cortisol from children’s baseline sample to their peak post-stressor sample. Moreover, children’s PE significantly decreased and NE significantly increased during the stressor, providing further support for the validity of the stress-inducing nature of the paradigm. Additionally, children’s PE and NE during the task were significantly associated with individual differences in their cortisol responses. Our findings highlight the challenges for neuroendocrine researchers with respect to obtaining mean increases in preschoolers’ cortisol reactivity in the laboratory and have important methodological implications, particularly regarding the importance of collecting multiple post-stressor samples.     

An experimental treatment using verbal punishment with two preschool stutterers

A multiple base-line experimental treatment was conducted with two preschool stuttering children. Each child conversed 20 min with the experimenter for 20 sessions. Treatment consisted of the presentation of the verbal stimulus “slow down” contingent upon a stuttering response. The percentage of words stuttered by both children decreased during the treatment sessions. Probe tape recordings conducted in each child's home revealed a decrease in stuttering frequency.     

Effect of swimming session duration and repetition on metabolic markers in rats

The aim of this study was to investigate the profile of metabolites in male rats subjected to 50-60 min of swimming on three protocols: group A, a single 50 min swimming session; group B, one session a day for three days (5 min on day 1, 15 min on day 2 and 30 min on day 3); and group C, one session a day for 5 days, with increasing duration from 5 min on day 1, 15, 30, 45 and 60 min on consecutive days. The interval between sessions was 24 h. Measurements were made after the last swimming session. Controls did not swim. The glycogen content of liver and gastrocnemius and soleus muscle was depleted in the three groups that swam, but blood glucose concentration was significantly increased only in group B. Serum lactate concentrations were greater than the controls in groups A and B. There were significant increases in serum free fatty acid concentrations in all groups that swam. The increases in plasma free fatty acids may have resulted from lipolysis stimulated by endogenous catecholamines in groups A and C, since basal lipolysis measured in vitro was unchanged by swimming. The large increase in basal lipolysis in group B may have contributed to the rise in plasma free fatty acids. Adipocytes from rats in groups A and B were supersensitive to epinephrine, whereas those from group C were not. We conclude that the metabolic alterations were less pronounced after the last of five swimming sessions over 5 days than after a single session, even though session duration and the contribution of the physical component were similar. Glucose mobilization, but probably not utilization, was similar in the three groups that swam. The mechanisms of lipid mobilization from adipose tissue differed, depending on the stress paradigm. The metabolic changes in groups A and B indicated that three daily swimming sessions were insufficient to cause adaptation. The results contrast with previous findings for foot-shock stress, which leads to sensitization rather than adaptation in response to repeated stimuli.     

Infant-holding bias variations in mother–child relationships: A longitudinal study

This longitudinal study examined the associations between maternal depressive symptoms and infant holding bias in a sample of N = 43 women during three prospective sessions: during pregnancy, two months after childbirth, and when the child was 19 months of age. The majority of mothers (65.8% on average) held their children on the left side of their body at all three sessions; approximately 30% demonstrated a change in their preference, in particular between the pre- and first post-natal session. Examination of reciprocal associations between holding bias and depression revealed that prior and concurrent depression did not predict changes in holding-side biases, whereas women's holding preferences when their infant was two months old predicted change in pre- to postnatal depressive symptoms; women favouring a right-sided holding bias were significantly more likely to report increased depressive symptoms across the perinatal period, whereas a left-sided holding bias was associated with decreased depressive symptomatology.     

THE TRAINING AND GENERALIZATION OF A CONVERSATIONAL SPEECH FORM IN NONVERBAL RETARDATES1

Differential reinforcement and imitation were used with two retarded children to train three sequential verbal responses associated with the display of a picture and questions related to that picture. Each response consisted of a three-word chain in sentence form; combined with verbal responses from the experimenter, this trained sequence formed a short conversational unit. Three experimenters measured the use of each sentence in settings different than the one in which training took place, and with pictures different than those used during training. Two types of generalization sessions were used: (1) General sessions, during which 10 pictures never used during training were displayed to the subject with reinforcement delivered on a noncontingent basis, and (2) Intermixed sessions, during which 10 pictures never used during training were displayed to the subject, but a picture having received training was also displayed, and correct responses to this picture were reinforced on a variable schedule. Both subjects learned the sentences being trained. However, little generalization was evident from this training when all experimenters conducted General probe sessions. Generalization occurred with one experimenter only after that experimenter conducted Intermixed probe sessions. Generalization to a third experimenter was then observed (i.e., after the first two experimenters had conducted Intermixed probe sessions) without the use of Intermixed probe sessions by this third experimenter.     

Development of social responses in two severely retarded children

The effect of reinforcement dependent on the social responses of two severely retarded withdrawn children was investigated. During 30 training sessions (30 min each) food and praise were administered dependent upon the children's mutual participation in a ball-rolling and block-passing task. Both children showed a progressive increase in social interaction in a non-training situation during this reinforcement period. After the reinforcement procedures were removed, social behavior decreased markedly. Response generalization to children not involved in training occurred.     

Learning in a task of complex auditory streaming and identification

Adult humans were studied for improvements in their ability to segregate natural whole speech in background noise, in 6 test sessions spaced with a very wide range of inter-session interval (ISI) ranging from minutes to weeks apart so as to examine the effect of this parameter on initial (early) and late components of perceptual learning. Improvements were found even with spacings of 3 weeks between the punctate task sessions. All subjects showed similar total learning amounts but there were sex- and ISI-dependent differences in learning patterns, which we indexed by dividing the overall exponentially-decreasing learning pattern into an early phase between the first two sessions and a later phase between the second and sixth sessions. Males tested at all ISIs and females tested at short (2, 5 and 15 min) and long (1–21 days) ISIs showed small amounts of early-phase learning and large amounts of late-phase learning. However, females tested at intermediate (30 min and 1 h) ISIs showed only early learning, i.e., faster learning given that the total learning was the same. This sex- and ISI-specific deviant pattern could be changed to the standard pattern by interposing an overnight interruption that included sleep amongst test sessions. Thus, improvement in this complex auditory streaming and identification task can occur even with very brief and widely-spaced exposure, generally through a standard pattern of slower overall learning, but also through a sex- and ISI-specific deviant pattern of very rapid early learning which can be modulated by interposed delay unlike the standard pattern.     

Income maximizing on concurrent ratio-interval schedules of reinforcement

Three experiments examined the effect of food availability on pigeons' choice behavior under concurrent schedules of reinforcement. In Experiment 1, 3 pigeons earned their daily food ration by choosing, in 30-min sessions, between concurrent variable-ratio 30 variable-interval 40-s schedules. Food presentations during both schedules lasted 2 or 12 s, depending upon the condition. Relative variable-ratio response rate was inversely related to hopper duration. In Experiment 2, 4 pigeons received their daily feeding by responding on the same schedule pair as in Experiment 1 (with 4-s food presentations) in sessions that varied in length from 10 to 30 min, depending on the condition. The length of a vertical slit projected on a response key increased with time so that “passage of time” might be more easily discriminable. As session duration decreased, relative variable-ratio response rate increased. In Experiment 3, 4 pigeons chose between two variable-interval 40-s schedules. One schedule operated without regard to the schedule selected, whereas the other operated only when the subject responded in its presence (dependent). Although these schedules had the same feedback function, preference for the dependent variable interval increased as session duration decreased from 30 to 10 min. The preference changes in these studies reveal the operation of an income-maximizing process in choice.     

Effects of toy guns and airplanes on children's antisocial free play behavior.

The effects of toy guns and toy airplanes on children's antisocial (aggression and rule-breaking) behavior was investigated in two settings (ten children in Study I and 13 in Study II) during 30-min free play sessions. Four-and 5-year-old children were observed during 15–16 free play sessions. During some sessions the children played either with (novel, aggressive) toy guns or with (novel, nonaggressive) toy airplanes in addition to their usual toys. In both studies, the toy guns treatment produced a reliably higher rate of antisocial behavior than the average of the toy airplaines and the usual toys. The novel-nonaggressive toy airplanes also increased the rate of antisocial behavior as compared to usual toys in Study II. The results were related primarily to Berkowitz's and Bandura's analyses of aggressive behavior, but they were related also to other theoretical models which predict stimulus control of behavior.     

Trait predictors of placebo responses in itch

This study investigated trait predictors of placebo responses in the context of inflammatory skin reactions. This was a randomized, cross-over, experimental study using a deceptive placebo protocol. A healthy sample of volunteers (N = 48) completed online personality measures, then attended two laboratory sessions in which short-term inflammatory skin reactions were induced. One was a control session and the other the ‘treatment’ session in which a placebo cream was administered with the suggestion of a reduced skin reaction. A placebo response was defined as smaller skin reactions in control vs. treatment sessions. The traits ego resiliency and neuroticism were selected as possible predictors of placebo responses. Traits were selected in consideration of the two-faceted transactional model of placebo responsiveness and in light of empirical and psychometric considerations ego resiliency emerged as a consistent predictor of placebo responses in itch (p < .05). This is the first study to identify trait predictors of placebo responses in inflammatory skin reactions. Ego resiliency may typify greater placebo responsiveness; however, this may only be in certain contexts. Matching treatment approaches to bio-behavioural response tendencies may be useful clinically if the placebo component of traditional treatments can be enhanced.     

Rapid acquisition of a sidman avoidance response

Rats were trained on a Sidman avoidance task with a 22-sec R-S and a 6-sec S-S interval for six daily 30-min training sessions. Disabling the response lever during and 0.5 sec after shock termination represented one factor in the 2 by 2 factorial design and the presentation of a feedback light cue accompanying an effective response was the other. Rats in the lever-disable condition with feedback light made significantly more avoidance responses than the other treatment groups. In a second experiment, daily 60-min sessions were observed. Using a lever-disable plus feedback light treatment, rats made more avoidance responses and received fewer shocks during the second 30-min as opposed to the first 30 min period.     

Conditioned suppression by a stimulus associated with nalorphine in morphine-dependent monkeys

Three rhesus monkeys, physically dependent on morphine, were trained to press a lever for food on a fixed ratio of 10 responses. A tone, initially a neutral stimulus, was aperiodically presented every third or fourth session, 5 min before and after the intravenous injection of nalorphine, a morphine antagonist which produces an immediate withdrawal syndrome in morphine-dependent monkeys. After several sessions, conditioned suppression of food-lever response rate was observed. Conditioned bradycardia, emesis, and excessive salivation also occurred. In 40 to 45 sessions the conditioned suppression of food-lever response rate and the conditioned autonomic changes were extinguished by presenting pairings of a tone and saline injection. The monkeys were then reconditioned by presenting the tone aperiodically, every third or fourth session, 5 min before and after the intravenous injection of nalorphine. Results were similar to the initial conditioning sessions. Two rhesus monkeys not dependent on morphine were stabilized on a food schedule similar to that used for the first three monkeys. These monkeys showed no change in food-lever response rate during or after nalorphine injections.     

ON THE INABILITY OF INTERVAL TIME SAMPLING TO REFLECT FREQUENCY OF OCCURRENCE DATA1

Interval time sampling yields the result, percentage of intervals scored. It is rudimentary to note that this measure per se does not constitute a response dimension. It is a useful behavioral measure, therefore, only to the extent that it accurately reflects the nature and degree of the fundamental dimensions from which it is drawn i.e., frequency and duration. The correspondence between scored intervals and response duration is fairly well understood (Journal of Applied Behavior Analysis, 1975, 8 , 463–469; 1977, 10 , 325–332). This study determined the correspondence between scored intervals and response frequency. Eleven, 30-minute experimental sessions that differed along the variables of frequency of occurrence and time per response (the average length of a response per session) were computer simulated. In the first group of four sessions, the frequencies were 45, 100, 150, and 300; in these sessions, all responses ranged from one to three seconds. In the second group of four sessions, the frequencies were 31, 61, 101, and 152; in these sessions, all responses ranged from three to nine seconds. In the last group of three sessions, the frequencies were 25, 34, and 50; here, all responses ranged from nine to 27 seconds. The response distribution within the above ranges was rectangular, with each whole second represented once. The responses were selected by a random number generator, and on each trial every number in the distribution had an equal probability of occurrence. These provisions produced a linear pattern of responding. The time per response in the three groups of sessions were 2, 6, and 18 seconds. For all sessions, event recordings were made and analyzed. The analysis consisted of using partial interval time sampling to determine the percentage of intervals scored; this total was subdivided into intervals containing (1) single responses, (2) multiple responses, (3) continuing responses, and (4) response initiations or terminations. The analysis was performed when the length of the observation interval was 5, 10, 20, 30, 60, and 120 seconds. An additional session drawn from a study that contained real-life data was subjected to this same analysis. The most significant results were derived by finding the ratio of scored intervals containing single responses to the total intervals scored. If every scored interval contained a single response, this ratio would equal 1.0; if no scored interval contained a single response, the ratio would be 0.0. It can be seen that this ratio is an objective expression of the validity of interval time sampling as a measure of response frequency. Of 66 data points (11 sessions × six observation lengths per session), only five were equal to or greater than 0.80. These five points were all found in just two sessions (f = 45, 100). A validity index of less than 0.50 was observed in 49 of the 66 points. Also, the validity index increased, peaked, and then decreased within sessions as the length of the observation interval was increased. The results from the real-life session were in close agreement with those obtained from the simulations. The importance of these and previous findings lies in the demonstration that changes in scored intervals need not represent true behavior change. The data indicate that there are many combinations of behavioral frequency and duration where interval time sampling cannot produce valid measurement results.     

The Effect of Induced Mood on Children’s Social Information Processing: Goal Clarification and Response Decision

We investigated whether induced mood influenced the social information processing steps of goal clarification and response decision in 480 1st–3rd graders, and in more selected groups of low accepted-aggressive (n = 39), average accepted-nonaggressive (n = 103), and high accepted-nonaggressive children (n = 68). Children participated in two sessions; in the first session peer assessments were administered. In the second session children were randomly assigned to receive either a happy, angry, or neutral mood induction prior to participating in a social cognitive interview assessing goals, outcome expectancies, and self efficacy for competent, hostile, and passive responses in the context of ambiguous provocations. Results revealed that an angry mood increased focus on instrumental goals. Low accepted-aggressive children were more susceptible to the effects of mood than were high accepted- and average-nonaggressive children. In addition, children’s predominant goal orientation was related to children’s response decisions; children with predominantly instrumental goals evaluated nonhostile responses to provocation more negatively and had higher self efficacy for hostile responses. Implications and future research directions are discussed.     

Imitation as a learning strategy in the acquisition of vocabulary

Twenty-four 14- to 30-month-old children observed a model use 20 new words as labels for objects of varied semantic associations. Acquisition of the new words was clear in both elicited and spontaneous imitation by the children and in generalized use of the words. Age was highly and positively correlated with elicited and spontaneous imitation and scores for recognition of the objects associated with the words. Imitation and recognition scores were highest for words associated with food and active objects and low for passive objects and words with no associations. Older children's use of the words immediately after the model's use increased rapidly with the first two presentations, and their use of the words prior to the model's use showed an increasing trend over the series of modeling sessions. Younger children responded at a lower rate.     

DIFFERENTIALLY REINFORCING LOW RATES OF MISBEHAVIOR WITH NORMAL ELEMENTARY SCHOOL CHILDREN1

Effective nonpunitive procedures for reducing counterproductive classroom behaviors are of potential benefit to both students and teachers. A recent strategy for dealing with this class of problem behaviors involves the reinforcement of acceptably low levels of such behavior. The laboratory version of this procedure, called differential reinforcement of low rates of responding (or DRL), provides for a reinforcer to be delivered contingent upon a response that is separated from the last preceding response by a minimum amount of time. To make this procedure more amenable to classroom use, the present authors have modified it so that a reinforcer is delivered if fewer than a specified number of responses occur within a preset time interval (Deitz and Repp, Journal of Applied Behavior Analysis, 1973, 6 , 457–463). Previous studies using this procedure have found it effective in reducing and maintaining low rates of targeted behaviors. However, these effects have been demonstrated with groups of subjects and/or individuals from dependent populations. The present study investigated use of this modified DRL procedure with individual students in normal elementary classrooms. In the first of three studies, “talk-outs” of an 11-yr-old fifth-grade male were reduced when nonexchangeable gold stars were made contingent on two or fewer responses per session. During baseline sessions, an average of 4.45 talkouts were observed per 45-min session. Average responding subsequently fell to 1.83 when the modified DRL contingency was applied, increased to 7.60 during a reversal phase, and dropped again to an average of 1.20 when the contingency was reapplied. In the second study, out-of-seat behavior of a 12-yr-old sixth-grade female was reduced when gold stars were made contingent on two or fewer responses per 45-min class period. Baseline responding averaged 6.10 responses per session. When the contingency was applied, average responding fell to 0.16. During the reversal period, responding increased to an average of 6.00 and fell again, after the contingency was re-introduced to an average of 0.40. In the third study, a reduction in both talking-out and out-of-seat behaviors of another 11-yr-old fifth-grade male was demonstrated with a multiple-baseline design. Using different lengths of baselines, gold stars were made contingent first on a low rate of out-of-seat behavior, and then on a low rate of talk-outs. Out-of-seat responding fell from a baseline average of 7.50 to a treatment average of 1.14. Talk-outs went from a baseline average of 4.66 to a treatment average of 1.14. In all three studies, the modified DRL procedure proved effective with the children and was manageable by the classroom teacher. For the students, nonexchangeable conditioned reinforcers (stars) were sufficient to maintain lowered rates of inappropriate behavior with the modified DRL schedule; there was no need for an elaborate token economy, a process that in many cases may be only a form of behavioral “overkill”. As in other studies investigating DRL schedules, students were not informed of their accumulation of responses; the differential effects of providing or withholding this feedback need to be investigated. Overall, these studies add single-subject replication with normal children to the literature on modified DRL procedures.     

Varying temporal location of a conditioned stimulus in heart rate conditioning ofMacaca mulatta

The several functions that a stimulus can assume were investigated in a Pavlovian conditioning procedure. The subjects were six rhesus monkeys; the response under observation was heart rate. The conditioning began with a temporal separation of zero between a signal and a regularly repeating electric shock; the signal was then moved to a series of earlier locations in the inter-shock interval. After six sessions at each location, two sessions followed in which only the shock was delivered periodically. The findings included: (1) A two-phased conditioned cardiac rate response seen at the first location became more multiphasic and irregular during longer intervals between signal and shock; (2) the location where the conditioned response peaked became increasingly variable as the signal was moved back, but this variability maintained a constant proportion to the signal-shock interval; and, (3) heart rate during a presignal period, and during a comparable period in shock only sessions, was generally deceleratory early in training and acceleratory thereafter. Sessions with the signal showed heart rate in the presignal period to have become acceleratory earlier in training than sessions with shock only. The data pertain to stimulus control over heart rate as a function of: (A) the temporal proximity of a signal to an aversive stimulus; and, (B) the presence or absence of the signal. The use of appropriate response units in cardiac conditioning is also discussed.