Choice between delayed reinforcers in an adjusting-delay schedule: The effects of absolute reinforcer size and deprivation level

Choice between two reinforcers differing in magnitude and delay was investigated in rats using an adjusting-delay discrete-trials schedule in which the two reinforcers were associated with two levers (A and B). The delay to Reinforcer A (the smaller reinforcer) was always 2 sec, whereas the delay to Reinforcer B was varied in accordance with the distribution of choices in successive blocks of trials. In Experiment 1, the mean delay to the large reinforcer during the last 5 of 60 training sessions was greater when the rats were maintained at 80% than when they were maintained at 90% of their free-feeding body weights. In Experiment 2, the delay to the larger reinforcer was greater when the two reinforcers consisted of one and two 45-mg food pellets than when they consisted of three and six pellets. The results are consistent with a model of “self-control” which posits hyperbolic relations between reinforcer value and reinforcer magnitude, and between reinforcer value and delay of reinforcement.     

Slower eating rate reduces the food intake of men, but not women: implications for behavioral weight control

This study tested a central tenet of behavioral weight control: does slower eating rate reduce food intake and positively affect appetite ratings. This study used direct behavioral observation of participants' (n=48; 25BMI35) eating behavior using Universal Eating Monitors. Food intake and ratings of "desire to eat" (collected each minute during meals) were represented as a function of time. Based on an acclimation meal, participants' eating rate was modified by instructing them to eat a bite of food when prompted by a computer, which generated three types of meals: (1) baseline (eating rate was the same as the acclimation meal), (2) reduced-rate (eating rate was reduced by 50%), and (3) combined-rate (eating rate at the beginning of the meal was identical to that of the acclimation meal, subsequently eating rate was reduced by 50%). All meals were ad libitum. Slower eating rate during the reduced-rate and combined-rate meals resulted in less food intake compared to the baseline meal for men, but not women. Ratings of desire to eat, normalized for the amount of food consumed, were lower during the combined-rate meal for men and women. Thus, this basic premise of behavioral weight control was supported for men, but not for women.     

Substitution effects in a generalized token economy with pigeons

Pigeons made repeated choices between earning and exchanging reinforcer‐specific tokens (green tokens exchangeable for food, red tokens exchangeable for water) and reinforcer‐general tokens (white tokens exchangeable for food or water) in a closed token economy. Food and green food tokens could be earned on one panel; water and red water tokens could be earned on a second panel; white generalized tokens could be earned on either panel. Responses on one key produced tokens according to a fixed‐ratio schedule, whereas responses on a second key produced exchange periods, during which all previously earned tokens could be exchanged for the appropriate commodity. Most conditions were conducted in a closed economy, and pigeons distributed their token allocation in ways that permitted food and water consumption. When the price of all tokens was equal and low, most pigeons preferred the generalized tokens. When token‐production prices were manipulated, pigeons reduced production of the tokens that increased in price while increasing production of the generalized tokens that remained at a fixed price. The latter is consistent with a substitution effect: Generalized tokens increased and were exchanged for the more expensive reinforcer. When food and water were made freely available outside the session, token production and exchange was sharply reduced but was not eliminated, even in conditions when it no longer produced tokens. The results join with other recent data in showing sustained generalized functions of token reinforcers, and demonstrate the utility of token‐economic methods for assessing demand for and substitution among multiple commodities in a laboratory context.     

Role of fatty acid oxidation in control of meal pattern

To characterize the role of fatty acid oxidation in the control of food intake, we investigated the effect of 2-mercaptoacetate, which inhibits fatty acid oxidation, on meal patterns and cumulative food intake in rats. Rats were fed either a medium fat (MF, 18% fat) or a low fat (LF, 3.3% fat) diet. Mercaptoacetate (400 mumole/kg body wt), intraperitoneally injected in the middle of the bright or at the onset of the dark phase of the diurnal lighting cycle, increased cumulative food intake in MF rats by shortening the latency to eat after injection and the duration of the subsequent intermeal interval (IMI) without affecting the size of the first meal. Mercaptoacetate, injected in the middle of the bright phase, reduced the latency to eat but did not affect the duration of the subsequent IMI or cumulative food intake in LF rats. A higher dose of mercaptoacetate (600 mumole/kg body wt), initially increased and later decreased cumulative food intake in MF rats. The initial increase in food intake was due to shorter IMIs; the subsequent decrease in food intake was due to smaller meals after mercaptoacetate injection than after control injection. The results indicate that a drop in fatty acid oxidation caused by mercaptoacetate triggers a meal. This implicates fatty acid oxidation in the maintenance of postprandial satiety.     

Superconditioning from a reduced reinforcer

In four autoshaping experiments pigeons received conditioned inhibition training of the form A++, AB-, where ++ is a strong reinforcer and - is nonreinforcement. Subsequent AB+ training, in which + is a moderate reinforcer, resulted in enhanced conditioning of A, relative to an A stimulus receiving no treatment, one receiving A+ treatment, and one receiving A++ treatment. This enhancement of conditioning to Aconstitutes a demonstration of “superconditioning”. The presence of the inhibitory B sufficiently enhanced the reinforcing power of the moderate reinforcer (+) that it was able to further increase the excitation controlled by A. This occurred even though A had previously been paired with a stronger reinforcer (++). Superconditioning was also observed when A and B were extinguished prior to treatment with + or were originally neutral stimuli followed by + in the presence of an inhibitor trained elsewhere.     

Repetition Priming Follows Spontaneous but not Prompted Recognition of Familiar Faces

Reaction times to make a familiarity decision to the faces of famous people were measured after recognition of the faces in a pre-training phase had occurred spontaneously or following prompting with a name or other cue. At test, reaction times to familiar faces that had been recognized spontaneously in the pre-training phase were significantly facilitated relative to an unprimed comparison condition. Reaction times to familiar faces recognized only after prompting in the pre-training phase were not significantly facilitated. This was demonstrated both when a name prompt was used (Experiments 1 and 3) and when subjects were cued with brief semantic information (Experiment 2).

Repetition priming was not found to depend on prior spontaneous recognition per se. In Experiment 3, spontaneously recognizing a familiar face did not prime subsequent familiarity judgements when the same face had only been identified following prompting on a prior encounter. In Experiment 4, recognition memory for faces recognized after cueing was found to be over 90% accurate. This indicates that prompted recognition does not yield repetition priming, even though subjects can remember the faces. A fusion of “face recognition unit” and “episodic record” accounts of the repetition priming effect may be more useful than either theory alone in explaining these results.     

The development of socialization skills in an electively mute child

In a booth designed especially for work with both autistic and electively mute children, a 4-yr-old girl named Dolly, who had no communicative speech or imitative skills, was given a preliminary session in which her verbal output was assessed. To elicit sounds from Dolly, an instrument called a “color organ” was used as a positive reinforcer. After this baseline assessment, in 40 half-hour sessions, Dolly was taught to make eye contact with E, and to obey instructions—although it was first necessary to extinguish her disruptive behavior, particularly her opérant crying. In addition, she learned non-verbal imitative behavior, such as hand clapping; and verbal imitative behavior, such as saying “Hi!” Social (play) sessions were begun after session 21, and continued for the remaining time. These were helpful in generalizing Dolly's learned skills to an environment other than the booth; and to other tasks, such as singing “Ee-eye-ee-eye-oh” in the refrain of the song, “Old McDonald”; and pointing to E's eyes, saying “ice”.     

An experimental approach to the reduction of overactive behavior

An operant, differential reinforcement procedure (DRO) was employed in a playroom setting for the purpose of controlling overactivity. Six overactive, mentally retarded children, aged 8–13 yr were first observed individually for a period of 8 days in the playroom in order to obtain a baseline performance on a specially constructed check-list of hyperactive behavior. Following this, the conditioning phase began under a fixed schedule of reinforcement with tokens as the reinforcing agents (later to be exchanged for candy). A fading-out phase was instituted after the 30-day conditioning period in order to maintain resistance to extinction at a higher level. Post-conditioning observations were then made. It was conclusively shown that the disturbed, hyperactive behavior came under stimulus control with “grasshopper” play decreasing substantially during the latter part of conditioning and extinction periods.     

Group play therapy and tangible reinforcers used to modify the behavior of 8-yr-old boys

Eleven third-grade boys were randomly assigned to three play therapy groups. The boys had been referred by their teachers because of shy, withdrawn behavior. The Token Group met in a play group (4 Ss), had a therapist, and received tangible reinforcements for social approach behavior. The Verbal Group (4 Ss) was treated similarly to the Token Group except that no tangible reinforcements were used. The Control Group (3 Ss) met in a play group without a therapist present. Fourteen play sessions were held for each group. The Token Group changed more than the Verbal Group; the Verbal Group changed more than the Control Group; the Control Group showed no change on the objective measures used. The Token Group exhibited an increase in social approach behavior and a decrease in discrete, problem behavior. The Verbal Group increased slightly in social approach behavior. All groups failed to demonstrate changes in “productivity”, “anxiety” and “general psychological adjustment”.     

Choice between delayed reinforcers in a discrete-trials schedule: The effect of deprivation level

Choice between two reinforcers differing in magnitude and delay was investigated in rats using a discrete-trials schedule in which the two reinforcers were associated with two levers (A and B); in each session 5 free-choice trials (A and B both available) were interspersed among 44 forced-choice trials (A alone, 22 trials; B alone, 22 trials). In Experiment 1, preference for the more concentrated of two sucrose solutions declined as the delay to that reinforcer was progressively increased. In Experiment 2, progressively increasing the delay to both reinforcers by the same amount resulted in a shift in preference away from the less concentrated solution. In Experiment 3, it was found that the decline in preference for the more concentrated solution as a function of the delay to that reinforcer was steeper when the rats were maintained at 90% than when they were maintained at 80% of their free-feeding body weights. This effect of deprivation level on choice is inconsistent with some current models of “self-control”.     

Parametric analysis of delayed primary and conditioned reinforcers

We examined the effects of delayed reinforcement on the responding of individuals with intellectual disabilities. Three conditions were evaluated: (a) food reinforcement, (b) token reinforcement with a postsession exchange opportunity, and (c) token reinforcement with a posttrial exchange opportunity. Within each condition, we assessed responding given (a) a no‐reinforcement baseline, (b) immediate reinforcement, and (c) delayed reinforcement, in which responses produced a reinforcer after 1 of 6 delays. Results suggest that delayed food produced greater response persistence than did delayed tokens.     

Shorter articles and notes the interpretation of the passive voice

It was hypothesized that sentences in the passive voice emphasize the importance of the things referred to by their grammatical subjects to a greater extent than sentences in the active voice. Each subject had to produce simple diagrams to represent two sentences, one active and one passive, and it was assumed that the size of areas in these diagrams could be taken as an index of importance. In Group EQ, the sentences specified an equivalent arrangement of colours, e.g. “Red follows Blue,” “Blue is followed by Red”; in Group CO, they specified converse arrangements, e.g. “Red follows Blue,” “Red is followed by Blue.” The predictions, that (i) the subjects of all sentences would tend to be represented as larger than the objects, and that (ii) the subjects of passives would be represented as larger than those of actives, were confirmed.     

Repetition priming of face recognition

Three experiments investigating the priming of the recognition of familiar faces are reported. In Experiment 1, recognizing the face of a celebrity in an “Is this face familiar?” task was primed by exposure several minutes earlier to a different photograph of the same person, but not by exposure to the person's written name (a partial replication of Bruce and Valentine, 1985). In Experiment 2, recognizing the face of a personal acquaintance was again primed by recognizing a different photograph of their face, but not by recognizing the acquaintance from that person's body shape, clothes etc. Experiment 3 showed that maximum repetition priming is obtained from prior exposure to an identical photograph of a famous face, less from a similar photograph, and least (but still significant) from a dissimilar photograph.

We argue that repetition priming is a function of the degree of physical similarity between two stimuli and that lack of priming between different stimulus types (e.g., written names and faces, or bodies and faces) may be attributable to lack of physical similarity between prime and test stimuli. Repetition priming effects may be best explained by some form of “instance-based” model such as that proposed by McClelland and Rumelhart (1985).     

Control of the behavior of schizophrenic patients by food

Operant-conditioning principles using food as a reinforcer were applied to control the behavior of 45 chronic schizophrenic patients. The investigation was conducted in a psychiatric ward in which there was 24-hr environmental control.

In order to use food as a reinforcer for controlling psychotic behavior, it was necessary first to deal with the eating deficits in the patients. Approximately 50% of the ward population was selected because of a history of refusal to eat. Their refusal to eat had remained relatively unaffected by one or more of these treatments: spoonfeeding, tubefeeding, intravaneous feeding, and electroshock. These treatments were discontinued, and the patients were left alone at mealtimes. The results show that social reinforcement in such forms as coaxing, persuading, and feeding the patient tend to shape patients into eating problems so they are conditioned to eat only with assistance. When refusal to eat was no longer followed by social reinforcement, the patients soon started eating unassisted. When access to the dining room was made dependent upon a chain of responses including a motor and social component, all patients learned these responses.

     

Auditory and visual word-stem completion: Separating data-driven and conceptually driven processes

Two experiments investigated the contributions of data-driven and conceptually driven processing on an implicit word-stem completion task. In Experiment 1, individual words were studied either visually or auditorily and were tested using either visual or auditory word-stems. Keeping modality the same from study to test led to more priming than did changing modality, but there was reliable cross-modal priming. In Experiment 2, subjects read sentences like The boat travelled underwater and inferred the subject noun (i.e. “submarine”) or sentences like The submarine travelled underwater and categorized the subject noun (i.e. “boat”). At test, there was reliable priming for both actually read nouns and inferred nouns. In addition, a modality effect was evident for the actually read nouns but not for the inferred nouns. Taken together, these results imply that there is a basic conceptually driven contribution to priming plus an additional contribution of data-driven processing when surface form is the same at study and test.     

Primed lexical decision: Combined effects of the proportion of related prime-target pairs and the stimulus-onset asynchrony of prime and target

Lexical decisions to word targets preceded by associatively related word primes are generally faster than those to words following neutral primes, whereas, under certain circumstances, lexical decisions to words preceded by unassociated word primes are slower than those to words following neutral primes. An experiment is reported that investigates the influence of the proportion of related prime-target pairs in the set of materials and of the stimulus-onset asynchrony (SOA) of prime and target on these associative priming effects. Four levels of proportion and three levels of SOA are systematically varied. Both variables are found to affect the size of the associative priming effects. Furthermore, the data suggest interdependence between them. The magnitude of priming only varies with SOA if the proportion of related pairs is relatively large. In contrast, the amount of priming varies with proportion under all SOA conditions. The data are interpreted primarily in terms of two contextual processes, viz., “prime-induced attentional processing” and “post-lexical coherence checking”.     

Motivational control of instrumental performance: The role of prior experience of the reinforcer

In four experiments we investigated the conditions that are necessary for instrumental performance to adjust appropriately to a change in drive state. Rats were trained to press a lever and pull a chain concurrently, with one action being reinforced by sucrose solution and the other by food pellets. In Experiment 1 for animals that were hungry throughout training the rate of lever pressing in an extinction test under thirst was unaffected by the type of reinforcer produced by this action during training, even though the sucrose solution would maintain a higher rate than the food pellets during training under thirst. In contrast, animals that experienced the instrumental contingencies arranged by the concurrent schedule while thirsty at some point during training pressed the lever more during the extinction test under thirst when this action had been reinforced with the sucrose solution rather than the food pellets. The remaining three experiments demonstrated that for this incentive effect to occur it is sufficient that the sucrose solution be delivered non-contingently under thirst at some stage of training. Thus, it would appear that performance mediated by an instrumental contingency adjusts appropriately to reinforcer revaluation brought about by a drive shift only if the animals have had prior experience with the incentive under the test drive state. This observation was interpreted in terms of Tolman's “cathexis” theory of motivation.     

The effects of token procedures on a teacher's social contacts with her students

The effects of a token system on a teacher's rate of social contacts with her students were investigated in a public school kindergarten. A group of six children were observed daily during a 20-min handwriting lesson. The children were divided into two groups (A and B) of three children each. Five conditions were imposed sequentially: (1) baseline without tokens, (2) contingent tokens for Group A, noncontingent tokens for Group B, (3) contingent tokens for Group B, noncontingent tokens for Group A, (4) reinstatement of condition 2, and (5) contingent tokens for both groups. It was consistently observed that the teacher's rate of social contact was higher with the children receiving the contingent tokens than with those who received noncontingent tokens.     

Changes in rate of schedule-induced behaviour in rats as a function of fixed-interval schedule

Two experiments were conducted to determine the way in which rate of adjunctive drinking and food-tray responding vary as a function of interreinforcement interval duration. In Experiment I rats were tested under fixed-interval schedules ranging from 1-60 s in duration, and in Experiment II under fixed-interval schedules ranging from 1-180 s in duration, with food as the reinforcer. The rate of drinking increased and then declined as interreinforcement interval increased, reaching a maximum under intervals of about 45 s. The rate of food-tray responding declined over the whole range of schedules. It is concluded that drinking can meaningfully be described as “schedule-induced”, in the sense of being directly facilitated by intermittent schedules of reinforcement; but this is less certain in the case of food-tray responding.     

Sensory-specific satiety is intact in amnesics who eat multiple meals

What is the relationship between memory and appetite? We explored this question by examining preferences for recently consumed food in patients with amnesia. Although the patients were unable to remember having eaten, and were inclined to eat multiple meals, we found that sensory-specific satiety was intact in these patients. The data suggest that sensory-specific satiety can occur in the absence of explicit memory for having eaten and that impaired sensory-specific satiety does not underlie the phenomenon of multiple-meal eating in amnesia. Overeating in amnesia may be due to disruption of learned control by physiological aftereffects of a recent meal or to problems utilizing internal cues relating to nutritional state.