Differences in food consumption under intermittent and continuous reinforcement schedules of water delivery: Some implications for schedule-induced behavior

Consumption of food pellets was examined in four water-deprived rats during 1-h sessions in which water was presented once every 30, 60, or 120 sec independently of the rats’ behavior according to three fixed-time (FT) schedules. Correlated with each FT condition was a continuous reinforcement (CRF) control condition in which the rats received, at the start of the session, the number of dipper presentations that were programmed to occur during the corresponding FT condition. During both the FT and CRF conditions, pellets per dipper presentation decreased and food intake rate increased with rate of water presentation, and there was a direct linear relation between log food intake and log water intake. For each of these three measures there was less eating under the FT condition than under the CRF condition, but the difference between the FT and CRF functions decreased at shorter FT values. These data are discussed in terms of the effects of amount of water on food consumption and the principle of temporal summation.     

Feeding ecology and laboratory predatory behavior toward live and artificial moving prey in seven rodent species

The present research related the feeding ecology of seven rodent species to the reactions of laboratory-reared and prey-inexperienced members of each species both to live prey and to an artificial moving stimulus predicting food pellets. Feeding ecology was determined by the degree of carnivory, based on reported stomach contents and observations of feeding. Experiment 1 assessed predatory reactions to a live cricket placed in each animal’s home cage. Killing and latency of eating the cricket were directly related to the degree of reported carnivory on moderately fast-moving arthropods. Experiment 2 examined behavior toward a rolling ball bearing that predicted delivery of food. Average percentages of trials with approach or contact of the bearing, and the conditional probability of a mouth contact were all positively related to the degree of reported carnivory and to cricket predation in Experiment 1. In addition, the topography of ball bearing contact for a species often resembled its topography of cricket contact. We conclude that (1) rodent predatory behavior can be studied in the laboratory using appropriate artificial stimuli and prey-inexperienced subjects, and (2) the predatory behavior of a species is based on underlying appetitive organization related to carnivory, including differential sensitivity to stimulus movement, motor preorganization, and susceptibility to conditioning. This appetitive organization appears to influence responding to both live and artificial prey.     

Instrumental response topographies of rats

Experiments 1, 2, and 3 showed that food-deprived rats responding for food pellets made significantly more long-duration leverpresses than water-deprived rats responding for water drops. These experiments further showed that this difference in instrumental response topography is long-lived, and depends neither upon idiosyncrasies of the experimental chamber nor upon severity of deprivation conditions. In Experiment 4, food-deprived rats responding for food pellets made significantly more long-duration leverpresses than did either food- or water-deprived rats responding for sucrose solution. Human judges in Experiment 5 were able to correctly identify instrumental leverpress responses by rats as being for food or water based solely on previous viewings of other rats drinking water or eating food pellets. It appears that instrumental response topographies in rats vary depending principally upon the reinforcer received, and that these instrumental response topographies resemble consummatory response topographies.     

Adjunctive behavior of the rat under periodic food delivery in a 24-hour environment

The behavior of 4 rats living in complex environments was monitored 24 h per day during free-feeding baseline and under conditions of periodic access to food. Under the periodic schedules, the minimum interfood interval (IFI) was increased from 16 to 512 sec in an ascending series. Periodic food produced robust overall increases in investigation of the feeder, drinking, general activity, and rearing, but not in wheel-running. The temporal distribution of behavior within the IFI was similar across subjects and supported the hypothesis that some responses were largely time-locked to the period immediately following eating, while other responses expanded to fill the interval. However, these response differences were not adequately captured by present classification schemes. Finally, the distribution of drinking following a food pellet strongly resembled the distribution of drinking following bouts of feeding in baseline. The results suggest that adjunctive behavior stems from three sources: (1) a simple increase in the number of opportunities for expression of normal preprandial and postprandial behavior, (2) an increase in the preprandial behavior directed toward the site of expected food, and (3) an increase in the postprandial distribution of both site-directed and more general exploratory behavior. These findings suggest that adjunctive behavior is not extraneous, but is an orderly distribution of responses ordinarily related to feeding and foraging for food.     

Meal size and intermeal interval both regulate schedule-induced water intake in rats

The present studies examined the effects of intermeal interval and pellet magnitude on the development and maintenance of schedule-induced polydipsia using a between-subjects design as contrasted with earlier investigations, which have exclusively employed within-subject procedures. In Experiment 1, pellets were delivered on one of six fixed-time schedules (20, 40, 60, 120,180, and 240 sec) to different groups of rats. Although the typical bitonic function relating water intake to intermeal interval was obtained, the function showed a wide plateau ranging from 60 to 180 sec. Experiment 2 demonstrated that both intermeal interval and pellet magnitude regulate schedule-induced polydipsia. While small-magnitude pellets could support drinking only at relatively short intermeal intervals, increasing pellet magnitude to medium or large resulted in drinking at progressively longer intermeal intervals. Indeed, we observed drinking on a fixed-time 720-sec schedule with large-magnitude pellets. These findings are derivable from the opponent-process theory of acquired motivation.     

Periodic water,interwater interval,and adjunctive behavior in a 24-hour multiresponse environment

To examine the generality of the interreward response effects shown by rats under periodic food delivery, we presented .10 ml of water at minimum interwater intervals that ranged from 8 to 512 sec. Use of a 24-h multiresponse environment allowed evaluation of interdrink responses with respect to their excessiveness, patterning, and functional relationship to the interwater interval. In contrast to the extensive activity-inducing effects of periodic food, the only major excitatory effect of periodic water was increased attention to the water source. Although there were a few bitonic and direct relationships between interwater interval and changes in responding, the great majority of functions were inverse or inconsistent. Further, unlike the increase in drinking under periodic food, total eating decreased under periodic water. The major similarity with food reward was the apparent separation of interreward behavior into three general classes of reward-appropriate foraging responses: area-restricted search after reward, more general search (and waiting), and focal search preceding the next reward delivery.     

Excitatory and inhibitory effects of free reinforcers

Rats’ responding was maintained on a random-interval 1-min food schedule. In addition, non-contingent pellets were delivered, independently of the animals’ behavior, at either fixed intervals (Experiment 1) or at random intervals (Experiment 2). As the rate of delivery of the periodic and aperiodic free reinforcers increased, the rate of responding decreased. But these free reinforcers, in addition to having this inhibitory effect, had also a local excitatory effect upon responding: lever-pressing increased to a level above its mean rate following the delivery of a free food pellet. The time course of this behavioral aftereffect of free reinforcers, for both fixed and random intervals, was dependent upon the proportion of the interval between successive free food deliveries. The relation of these results to those obtained with response-contingent reinforcement, free punishment, and in schedule-induced phenomena is discussed.     

Numerically restricted food intake in the rat in a free-feeding situation

Rats were trained to leave an array of food after they had consumed a fixed number (three, four, or five) of food items. This discrimination remained in effect despite a shift from 45-mg Noyes pellets to larger and irregularly sized sunflower seeds. The present demonstration replicates work first reported 50 years ago by Otto Koehler and his associates (e.g., Marold, 1939; see also Koehler, 1950), who used avian subjects, and, like those studies, it involved both positive and negative social reinforcement. The present procedure provided a rare instance in which numerical control was exerted over behavior that was primarily consummatory in nature. The results are viewed in terms of the wider literature of numerical competence in animals and are discussed in terms of a numerical process known asprotocounting (Davis & P’erusse, 1988b).     

Observing birth and placentophagia affects placentophagia but not maternal behavior of virgin rats

To determine whether observing components of periparturitional behavior affects the manifestation of those behaviors in virgin rats, virgins selected for nonplacentophagia and for the absence of spontaneous maternal behavior toward pups were exposed to stimulus rats that were giving birth, eating donor placenta, or eating lab chow. During observations, subjects could either eat donor placenta or just see and smell it. The subjects were tested subsequently for placentophagia and for the rate of onset of pup-induced maternal behavior. The results indicated that: (1) access to placenta in the presence of other rats led to placentophagia; (2) when such placentophagia occurred in conjunction with exposure to other rats that were giving birth or eating donor placenta, the subjects became permanent placentophages (otherwise, the subjects reverted and did not eat on subsequent placentophagia tests); (3) none of the observation conditions, regardless of the availability of placenta during observation, affected the maternal sensitization latency. The results are discussed in terms of social facilitation, exposure learning, and desensitization to exteroceptive stimuli.     

The functional equivalence of operant behavior and foraging

Many researchers have used the controlled procedures of operant methodology to test the predictions of foraging theory on the assumption that foraging is operant behavior and operant behavior is foraging. This experiment tested the assumption that leverpressing is functionally equivalent to search effort. Four rats were exposed to two situations: a naturalistic foraging situation (a “patch”) and a standard operant chamber. Each condition represented a different prey density on the patch and a corresponding change in the probability of reinforcement in the chamber. The average number of presses per pellet was linearly related to the density of pellets on the patch. This result indicates that leverpresses were functionally equivalent to search effort.     

Chapter 6 Is It True Eating Makes You Feel Better?:

The present study examined the relation between stress and eating in 25 bulimic women and 33 controls. Participants self-monitored calories consumed and stress levels over 5 days corresponding to the time just before and just after their psychology midtream exam. For both groups stress was not reduced in after eating. Suprisingly, for the bulimic group, the greatest reduction in stress occurred just prior to eating. These results are not consistent with current stress/coping models of bulimia which hypothesize the binge eating serves as a method of stress reduction and suggest that further evaluation on the relationship between stress and eating are needed.     

Schedule-induced behavior in rats: Pellets versus powder

Food-deprived rats develop polydipsia on an intermittent schedule (fixed time 60 sec) of food pellet delivery, but not on an identical schedule of food powder delivery. This result was demonstrated with separate groups receiving each type of food and was replicated using rats as their own controls. Powdered food not only prevented the development of polydipsia, but it abruptly terminated ongoing polydipsia in rats that were switched from the scheduled delivery of pellets to powder. Ethological analysis of the behavior showed that the rats receiving powder were not engaging excessively in some behavior other than drinking. After discounting several factors, we concluded that the amount of oral activity associated with feeding, which occurred immediately after food delivery, was reciprocally related to the level of drinking.     

Some further observations on serial enumeration and categorical flexibility

Rats were runway-trained in a variety of serial discriminations that involved three different reward outcomes: Noyes pellets (R), a Kellogg’s Corn Pop (R’), and 30 sec of confinement in an unbaited goal area (N). Each of three groups experienced a series that consisted of a single non-rewarded trip down the runway, irregularly mixed with a longer series that for one group (n = 3) consisted of three trips rewarded with the pellets, followed by a terminal nonrewarded trip (RRRN/N). A second group (n = 6) had the single N series mixed with a series that included an initial trip rewarded with a Pop, and three subsequent trips rewarded with pellets, pellets, and nothing, respectively (R’RRN/N). The remaining group was trained with an RRN/N series pair. The interval between trips within a series was about 20 sec, and the interval between series was about 10 min. All rats developed strong, accurate anticipation of the terminal nonreward event of the longer series. In a 4-day transfer shift phase, a matched one-half of the rats originally trained R’RRN/N were shifted to a new series pair, RRRN/NRRRN, as were all the animals trained RRN/N. The remaining one-half of the matched rats were shifted to RRN/NRRN, as were the animals originally trained on the RRRN/N series pair. The transfer to the new series was plainly more powerful in animals initially trained with the R’RRN series than it was in either of the control groups. This shift result is taken to mean that rats classified the differing motivational events of the R’RRN series into at least three numerical categories: (1) one R’, (2) two Rs, and (3) three rewards.     

Taste preferences as a function of food deprivation during original taste exposure

It has been reported previously that rats prefer a flavor they consumed under high deprivation to a flavor they consumed under low deprivation (Revusky, 1967). Here it was found that this preference occurs only if nutritive solutions are used and the flavors are given preceding and following eating. If flavors are given separately from the daily feeding, rats prefer the flavor given under low deprivation, whether or not a nutritive solution is used (Experiment 3). If flavors are given before and after the daily feeding, rats prefer the flavor they had under high deprivation (before feeding) more if sucrose solutions are used than if saccharin solutions are used and more on a high-deprivation test than on a low-deprivation test (Experiments 1 and 2). It was concluded that the “incentive value” of consumption is not necessarily higher under high deprivation than under low deprivation. The preference for the low-deprivation flavor obtained here may reflect a greater proportional rewarding effect of consumption under low deprivation or may reflect an aversion to the flavor consumed under high deprivation. Perhaps a small taste of flavor under high deprivation initiates responses of digestion that are unsatisfied and thus aversive, and the more so the higher the deprivation level.     

Effects of a dementia dietary educational program on nutritional knowledge and healthy eating behavior of family caregivers

ABSTRACT

Family caregivers play a critical role in dietary care and the nutritional status of people with dementia. The aim of this study was to investigate the effects of a family care-based dementia dietary educational program (DDEP) on family caregivers’ nutritional knowledge, healthy eating behavior and nutritional status of people with dementia. A total of 57 pairs of participants completed this longitudinal experimental study. Group A received routine care. Group B received the DDEP. Three outcomes were measured at pretest (T1), posttest (T2) and follow-up test (T3). Generalized estimating equations and regression were used to analyze the data. The scores of the caregivers’ nutritional knowledge significantly increased after receiving the DDEP in group B, and this increase was better than in group A. The posttest and follow-up test scores of healthy eating behavior were significantly higher than the pretest scores in both groups. The scores of nutritional status in group B increased from the pretest to the follow-up test, although there was no significant difference between the two groups. Some demographic factors played significant roles in the caregivers’ nutritional knowledge and healthy eating behavior. In sum, the DDEP improved the caregivers’ nutritional knowledge and healthy eating behavior for dementia. The demographic factors of family caregivers should be considered when providing nutritional information to enhance the nutritional status of people with dementia. The DHPDEP should be incorporated into the in-service education and training courses for nurses or dietitians who work with people with dementia.     

Rate of reinforcement and session duration as determinants of within-session patterns of responding

Rats pressed levers for Noyes pellets or keys for sweetened condensed milk reinforcers delivered by multiple schedules. Session length and baseline rates of reinforcement were varied in two experiments. Rates of responding increased during the early part of the session and then decreased for both responses and reinforcers, as well as for all subjects and values of the independent variables. Changes in response rates across the session sometimes exceeded 500%. Respoiise rates peaked approximately 20 min after the beginning of the session, regardless of session duration, when subjects responded on a multiple variable interval 1-min variable interval 1-min schedule. The function was flatter for longer sessions than it was for shorter sessions. The function was flatter, more symmetrical, and peaked later for lower rates of reinforcement than for higher rates of reinforcement. The function appeared early in training, and further experience moved and reduced its peak. Variables related to reinforcement exerted more control over some aspects of this function than did variables related to responding. These within-session patterns of responding may have fundamental implications for experimental design and theorizing.     

Serial pattern learning by rats: Transfer of a formally defined stimulus relationship and the significance of nonreinforcement

Two experiments with rats tested independent predictions from cognitive theories of serial pattern learning. The animals learned to anticipate, as measured by running times in a straight alley, different quantities of food pellets organized into formally defined, five-element serial patterns. In Experiment 1, for some animals the patterns were all formally structured according to a monotonic “less than” relationship in which any quantity was always less than its predecessor. For others, no consistent formal rule was applied. Results of a transfer test with a new pattern showed positive transfer if the formal structure of the new pattern was identical to that used initially, but negative transfer if the new pattern was formally different. In Experiment 2, two groups learned the monotonic patterns 18-10-6-3-1 or 18-10-6-3-0 food pellets, while two others learned the nonmonotonic patterns 18-3-6-10-1 or 10-3-6-10-0 food pellets. We asked if the difference in value of the terminal element, 1 or 0 food pellets, would affect the facility with which the patterns were learned. The results showed that learning rate and the qualitative response to the elements of the monotonie and nonmonotonic patterns were independent of the value of the terminal element. Both experiments lend additional support to the utility of using cognitive models of human serial-pattern learning for an analysis of the sequential behavior of nonhuman animals.     

Changes in unpunished responding during response-contingent punishment

In two experiments, gerbils that were punished for eating exhibited an increase in only the most probable of several ongoing alternative responses (running) during sessions when eating was suppressed. These results support previously suggested punishment and implicit avoidance rules for predicting the effects of response-contingent punishment in multiple-response baseline procedures. Most subjects also exhibited a decline in unpunished digging responses during punishment sessions. Neither this decline in the digging behavior nor the amount of increase in running behavior supported a quantitative constant proportion rule which predicts that each of the unpunished responses will increase to occupy a constant proportion of the time available to it.     

Childhood emotional abuse and disordered eating among undergraduate females: mediating influence of alexithymia and distress

OBJECTIVE: Drawing from stress-vulnerability and trauma theory (e.g., Rorty & Yager, 1996), this paper presents a model of associations among child emotional abuse (CEA), alexithymia, general distress (GD), and disordered eating (DE). This study extended previous research on psychological outcomes of child physical and sexual abuse to explore those of CEA using measures of specific emotionally abusive acts. METHOD: Five hundred and eighty-eight female university students completed self-report surveys consisting of measures of CEA, alexithymia, depression, anxiety, and DE. Structural equation modeling was used to test this conceptual model. RESULTS: Comparison between measurement models suggested that bulimic behavior is a separate construct from restrictive eating behaviors and body dissatisfaction. In the structural model with the best fit, the association between CEA and DE was mediated by alexithymia and GD (i.e., a component of depression and anxiety). Specifically, CEA was associated with alexithymia, which was further related to GD. Then, restrictive eating behaviors and attitudes mediated the relation between GD and bulimic behaviors. By analyzing a second, nested model, this latter pathway was shown to be important. CONCLUSION: While the best-fitting model is only one of many possibilities, these results point to a weak-but significant-complex relation between CEA and DE. They are associated through a series of mediating relations in a multivariate model including alexithymia and GD. The current study supports research suggesting that child emotional abuse can have a negative impact on its survivors. Treatment of those survivors manifesting disordered eating should be holistic, as opposed to targeted towards specific symptoms.     

College Students’ Relationship Between Trauma and Disordered Eating

Among college students, a correlation exists between trauma exposure and eating disorders. Although disordered eating behaviors are more prevalent than eating disorders, the relationship between different types of trauma exposure and disordered eating is unknown. The current study explored this relationship. One hundred two participants completed questionnaires on disordered eating and trauma exposure. Results showed that (a) sexual abuse was a significant predictor of concerns regarding food and weight gain (p < .05) and (b) other form of trauma (e.g., natural disaster) was a significant predictor of difficulties in individuals’ relationship with food (p < .05). Clinical implications, especially those related to trauma assessment and disordered eating behaviors, are discussed. The importance of examining the impact of nonsexual trauma is described, and the clinical utility of breaking eating pathology down into specific abnormal attitudes and behaviors is highlighted.