Polydipsia induced by a schedule of brain stimulation reinforcement

Rats pressed a lever for a signaled brain stimulation reinforcement on either fixed-interval or fixed-ratio schedules. Both schedules induced polydipsia, with a median water intake of 22.5 ml (about four times the control level) in 3-hr sessions. The stimulation did not directly elicit drinking or other behaviors. In a second experiment, two out of four rats became polydipsic during extinction following a continuous schedule of brain stimulation reinforcement. The results were compared with previous attempts to induce polydipsia with a schedule of brain stimulation reinforcement and were discussed in terms of polydipsia as a model of human “compulsive” behaviors.     

Category similarity effects in children's semantic memory retrieval

Fourth-, sixth-, and eighth-grade students were required to indicate whether or not a stimulus word belonged in either of two semantic categories that were held in memory. Each category pair was either semantically similar or semantically dissimilar. The results indicated that even for the youngest children, similar categories required less search time than dissimilar categories. It was suggested that while dissimilar categories had to be accessed successively prior to search, subjects were able to consolidate similar categories into a superordinate group which eliminated the time to shift from one category to another during search. The results were contrasted with clustering studies which have demonstrated a minimal amount of memory facilitation in children for conceptually related items over unrelated items.     

Food and intracranial stimulation responding suppressed with regular-interval shock.

Attenuation of conditioned suppression during intracranial stimulation was compared with that during food reinforcement. Response rates controlled by food and by brain stimulation were equalized on a multiple schedule by adjusting the stimulating current. When foot shock was delivered during timeout periods separating response components, responding for food was significantly more suppressed than responding for brain stimulation. When components were shortened from 10 to 2 minutes, responding maintained by either food or brain stimulation showed a similar temporal pattern of suppression preceding each shock, but responding in the component involving food remained significantly more suppressed. Explanations for the attenuated suppression during brain stimulation based on neural disruption, stimulus blocking, and analgesic properties were questioned. The increased responding during brain stimulation seemed to reflect greater response strength relative to food reinforced responding.     

Focal changes in cerebral blood flow produced by monetary incentive during a mental mathematics task in normal and depressed subjects

The purpose of this experiment was to determine the effect of incentive-induced arousal on the diffuse and regional cerebral blood flow (rCBF) response during cognitive activation for normal and depressed groups. Two normal rest CBF measurements were followed by two mental mathematics activation CBF measurements. For the first activation measurement, half the subjects in each group were offered monetary incentive for correct performance and half the subjects received no monetary incentive. All subjects were offered monetary incentive on the final activation run. The effect of monetary incentive on the first activation run was to increase CBF activation at four detectors in the left hemisphere. Incentive did not affect the CBF activation response when introduced following practice on the activation task (on the final run). Depressed groups had lower resting blood flow than normals, but the distribution of flow and the CBF response to incentive were almost identical in the two groups.     

Competition and cooperation between groups and between individuals

Groups and individuals were compared in two experiments. In the first, two same-sex individuals or two same-sex dyads played 10 trials of a Prisoner's Dilemma matrix game (PDG) for money. Play between individuals was more cooperative and less competitive than play between groups. In the second experiment subjects played 10 trials of either PDG or mutual-fate-control (MFC) matrices. For the MFC matrix the competitive choice, which reduces the opponent's outcomes, but has no effect on own outcomes, reflects a desire to increase one's relative advantage over the opponent. Although cooperation was greater for MFC, for both PDG and MFC matrices groups were more competitive and less cooperative than individuals. A large component of the groups-individuals effect is attributed to the greater desire of groups to “win” or avoid “losing” to the opponent, regardless of their absolute outcomes.     

Stimulus control and delayed reinforcement

Pigeons were tested for generalization along the line-orientation dimension, after being trained on various two-component multiple schedules. The first component contained either a variable-interval 1-min schedule of immediate reinforcement or an extinction schedule and was associated with a plain white key (S1). The second component contained a variable-interval 1-min schedule of delayed reinforcement and was associated with a black line on a white background (S2). The major results showed that (a) decremental gradients were obtained around the stimulus associated with the delayed reinforcement component when S1 was associated with extinction, but that incremental gradients were obtained when S1 was associated with immediate reinforcement, (b) the subjects' pretraining did not affect the generalization gradients if sufficient training on the terminal multiple schedule was provided, and (c) changing the S1 schedule from immediate reinforcement to extinction produced behavioral contrast if reinforcement was delayed for 10 sec during S2, but not if it was delayed for 20 sec.     

The use of averaged electroencephalic response techniques in the study of auditory processing related to speech and language

This paper reviews a number of studies done by the authors and others, who have utilized various averaged electroencephalic response (AER) techniques to study speech and language processing. Pertinent studies are described in detail. A relatively new AER technique, auditory brainstem responses (ABR), is described and its usefulness in studying auditory processing activity related to speech and language is outlined. In addition, a series of ABR studies, that have demonstrated significant male—female differences in ABR auditory processing abilities, is presented and the relevance of these data to already established differences in male—female language, hearing, and cognitive abilities is discussed.     

Automatic and conscious processing in retarded and nonretarded adolescents

Educable mentally retarded and nonretarded adolescents participated in incidental learning tasks that emphasized the utilization of processes that were consciously controlled but not deliberately aimed at memory (Experiment 1). Retarded individuals' performance on a standard recognition test was equivalent to that of nonretarded subjects following phonetic encoding and nonstrategic encoding, but was deficient following semantic encoding. Retarded subjects also demonstrated a lower level of performance on a rhyme recognition task. In Experiment 2, retarded subjects provided a pattern of responding identical to that of nonretarded subjects on a picture-word interference task designed to assess automatic processing. The two groups produced equivalent levels of semantic activation. It was argued that the results of the two experiments indicate deficient semantic processing on the part of retarded individuals relative to that of nonretarded individuals that cannot be accommodated by a structural-deficiency model, a developmental-lag model, or a hypothesis that predicts intelligence-related differences only when the task involves the use of deliberate mnemonic strategies.     

Memory for meaning in skilled and unskilled readers

Skilled and unskilled readers from grades 3, 5, and 7 (9, 11, and 13 years of age, respectively) performed one of three memory tasks on a randomized list of primary word associates. One group rated each word as “good” or “bad” (incidental semantic task), another group produced a rhyming word for each list word (incidental rhyming task), and a third group attempted to memorize the list (intentional learning task). The recall results indicated equivalent recall for skilled and unskilled readers at all grades on the rhyming and intentional tasks; whereas, skilled readers were superior to unskilled readers on the semantic task. A clustering analysis produced a similar effect as skilled readers, who performed the semantic task, tended to cluster semantically-associated words together during recall more readily than unskilled readers. The results were construed as evidence for reading-skill differences in the semantic encoding of individual words.     

Brain-stimulation intensity, rate of self-stimulation, and reinforcement strength: an analysis through chaining

Reinforcement strengths of different intensities of brain stimulation were assessed by means of a two-member behavioral chain. A variable interval schedule of 30 sec was the first-member, and five lever presses, each rewarded with stimulation, was the second. It was found that response rate on the VI schedule continued to increase beyond the intensity value which produced peak rate on the second-member, self-stimulation lever. It was concluded (1) that brain-stimulation reinforcement strength cannot be assessed adequately by means of self-stimulation rate, and (2) the chaining technique employed in the present experiment appears promising as an analytical tool in brain-stimulation research. Finally, some aspects of the data suggested a fatigue or stimulation-adaptation phenomenon.     

The acquisition of abstract letter codes

A modification of Posner's letter-matching paradigm proposed by Beller (1971) was employed to study the development of abstract visual and name codes for letters. Second-, fourth-, and sixth-grade students (ages 8, 10, and 12 years, respectively) were presented in advance one of a pair of to-be-matched letters. Case agreement (upper- and lowercase) between the prime letter and the letter pair was manipulated to differentiate facilitation based on concrete features of the stimulus letter from that based on the letter's abstract visual code. For physical matches second graders showed greater facilitation from same-case primes than from different-case primes, whereas sixth graders benefited equally from both types of prime. For same-name and different conditions, no qualitative developmental differences were revealed as all subjects benefited from letter primes irrespective of case agreement. The acquisition and utilization of abstract visual codes for letters are a later acquisition than name codes, which were clearly operative at the lowest grade level in the present experiment.     

Differential reinforcement of other-than-vocalization as a control procedure in the conditioning of infant vocalization rate

The purpose of the present study is to demonstrate reinforcement control over infant vocalization rates using a DRO schedule to control for elicitation of social stimulation. Mothers of four 2 1/2- to 3-month-old infants provided social reinforcement for their infants' vocalization under two schedules: continuous reinforcement (CRF) and differential reinforcement of other-than-vocalization (DRO). In a repeated-reversal single-subject experimental design, all four infants produced systematically higher vocalization rates during CRF, even though densities of social stimulation during DRO were equal to or greater than densities provided during CRF. Thus, whatever its elicitation value, social stimulation may reinforce infant vocalization rates.     

Focal changes in cerebral blood flow produced by a test of right-left discrimination

A sensorimotor control activation task was used to isolate the focal cerebral blood flow changes resulting from the visual and cognitive processing of a right-left discrimination task. Eleven normal right-handed males participated. The sensorimotor control task produced significant bilateral increases in flow in most cortical channels. Significant bilateral parieto-occipital activation was found for the right-left discrimination task over and above the flow changes produced by the sensorimotor control task. The left occipital flow increase resulting from the right-left discrimination task was found to be negatively related to task performance. An inverse relationship was also found between WAIS Performance IQ and the blood flow change in the left parietal channel. These results suggest areas for further testing concerning potential individual differences in cognitive processing during the performance of a right-left discrimination task.     

Positive reinforcement and suppression from the same occurrence of the unconditioned stimulus in a positive conditioned suppression procedure

Responding of rats was maintained on a variable-interval schedule of food reinforcement. The same response also produced a blinking light followed by electrical brain stimulation according to a fixed-interval schedule. This conjoint schedule produced two behavioral changes. First, instead of a steady rate of responding throughout the session, which would be characteristic of the variable interval food schedule alone, responding between occurrences of the light-brain stimulation pairings became positively accelerated and thus was more characteristic of the fixed-interval schedule of these pairings. Second, food responding was suppressed during the light that preceded brain stimulation. These results indicate that positive reinforcement and suppression resulted from the same occurrence of the light-brain stimulation combination. This finding suggests that stimuli such as conditioned reinforcers that precede an unconditioned reinforcer may have a suppressive effect upon responding in their presence that is being maintained by another reinforcer.     

Effects of unsignaled delay of reinforcement on preference and resistance to change

In Phase 1, pigeons were trained on a concurrent chain in which a 3-s unsignaled delay of reinforcement was imposed on responding in a terminal link in some conditions. Preference for that terminal link was always reduced in comparison with conditions in which there was no delay, substantially so for 3 of the 4 pigeons. In Phase 2, pigeons responded in a two-component multiple schedule. The scheduled rates of reinforcement were equal, but a 3-s unsignaled delay was imposed in one component. Resistance of responding to prefeeding and extinction was reduced in the delay component for the same 3 subjects for which the data had shown strong effects of delay on preference. Systematic observation revealed differences in response topography. In the delay component, subjects oriented more closely to the key and responses were less forceful compared with the no-delay component. Our results give further evidence that preference and resistance to change covary within subjects. However, they challenge the premise that the critical determiners of preference (i.e., terminal-link value) and resistance to change (behavioral mass) may be quantified purely in terms of stimulus—reinforcer relations.     

Behavioral contrast produced by a signaled decrease in local rate of reinforcement

Pigeons' key pecking in the presence of one stimulus (S1) was reinforced according to a response-dependent variable-interval schedule. Pecking rate during S1 increased (behavioral contrast) when a second stimulus (S2) [associated with either a response-dependent fixed-interval schedule (Experiment I) or a response-independent reinforcement schedule in which reinforcement availability was signaled by visual (Experiment II) or temporal (Experiment III) stimuli] alternated with S1. These experiments suggest that a discriminable, signaled decrease in local reinforcement rate during S2 is an antecedent of the behavioral contrast response rate increases during S1.     

Response strength in multiple schedules

In several different experiments, pigeons were trained with one schedule or condition of food reinforcement for pecking in the presence of one key color, and a different schedule or condition in the presence of a second key color. After responding in both of these multiple schedule components stabilized, response-independent food was presented during dark-key periods between components, and the rates of pecking in both schedule components decreased. The decrease in responding relative to baseline depended on the frequency, magnitude, delay, or response-rate contingencies of reinforcement prevailing in that component. When reinforcement was terminated, decreases in responding relative to baseline rates were ordered in the same way as with response-independent food. The relations between component response rates were power functions. Internal consistencies in the data, in conjunction with parallel findings in the literature, suggest that the concept of response strength summarizes the effects of diverse procedures, where response strength is identified with relative resistance to change. The exponent of the power function relating response rates may provide the basis for scaling response strength.     

Automaintenance,contrast, and contingencies: Effects of local vs. overall and prior vs. impending reinforcement context

The pigeon's keypeck was investigated in a variety of multiple schedules of response-independent or -dependent reinforcement. Experiments 1 and 2 found that keypecking developed to a reinforcement-associated cue that signaled an increase in local rate of reinforcement, but signaled either no change or a decrease in the overall rate of reinforcement, defined as that prevailing in the cue's absence. In Experiment 3 a greater rate of responding to a target stimulus was observed when it was preceded by a second signal—associated with the same, or a lower, rate of reinforcement—and followed by extinction than when this temporal sequence was reversed. In Experiment 4 responding to a target cue increased when either a temporally prior or a subsequent reinforcement-associated cue was changed to signal extinction. Experiment 5 examined the conditioned reinforcing effectiveness of target cues in two types of situations varying the local context of reinforcement. Stimuli associated with selected target components of a response-dependent multiple schedule of reinforcement could appear as the terminal-link consequences in a two-link chain schedule. Enhanced responding during a target cue which accompanied the introduction of an extinction period following this cue was paralleled by an increase in the conditioned reinforcement effects of this cue. No such increase was found for target cues in which an enhancement of responding had been produced by the interposition of an extinction period prior to the cue.