Range effects in successive discrimination

In two sets of experiments we examined pigeons' discrimination performance with a visual flicker-rate continuum, using a conventional successive discrimination procedure. In the first experiment, responses during the intermediate stimulus value were never reinforced, while responses during stimuli on either end of the continuum were reinforced periodically. In the second experiment, responses during stimuli from one end of the continuum were never reinforced, while responses during stimuli from the other end of the continuum were reinforced periodically. Results from both experiments show that discrimination between unchanged positive and negative stimulus values is a function of the range over which the total stimulus set varies. These range effects are comparable to effects found in absolute judgment tasks in human and animal psychophysics. In addition, the range effects reported here are not due to channel capacity, but may depend instead on variability in judgment criteria.     

Some effects of discriminable goal-box conditions on the learning of a successive discrimination

In an attempt to confirm and extend a previous reslt, rats were trained on two tasks where a signal delivered at the start of each trial indicated which of two paths through a maze would be rewarded. In Experiment I both paths led to the same goal-box, and it was found that performance was better when the state of the goal-box was different on trials with each of the two signals. In Experiment II the two paths led to spatially separated goal-boxes. It was found that when the states of the two goal-boxes were discriminably different but the state of each of them remained the same from trial to trial, performance was better than when their states varied irregularly. It is suggested that these results have interesting implications for theories of behaviour.     

Contrast discrimination under temporally varying contrast conditions

Psychophysical contrast discrimination of a 0.8-cpd vertical grating was tested using a paradigm that alternated test and masking gratings at 8 Hz. Masking contrasts were lower than, equal to, or higher than the test contrasts. Six test contrasts were combined factorially with six masking contrasts to generate a series of six contrast increment threshold versus test contrast curves (tvc curves). A particularly simple relationship existed between these curves. The curves could be brought into alignment by shifting them diagonally by the ratio of their masking contrasts. It is shown that this behavior is predicted by a model in which contrast gain is set by the average of the test and masking contrasts coupled with a simple model of contrast discrimination. Contrast gain control integrates contrast over a period of at least 125 msec, and contrast discrimination is a function of this time-averaged contrast.     

Simultaneous and successive syntheses and intelligence

Recent studies on information processing have developed an alternative model of mental abilities which constitutes an integration of Russian clinical research and North American factor analytic research. This model proposes that information may be processed in a simultaneous synthesis or a successive synthesis. The present study examines variations in these syntheses in three intelligence groups in order to identify the types of information processing characteristic of different intelligence groups. A stratified sampling of verbal and nonverbal IQ was used to select 60 boys of age 9–10 in each of three verbal IQ ranges: 71–90, 91–110, and 111–130. A battery of tests used in previous research was administered to all subjects. Multivariate analyses of variance and discriminant analyses indicated that the IQ groups differed markedly on tests used to identify simultaneous synthesis, most notably Raven's Progressive Matrices, and differed slightly less on tests of successive synthesis. Factor analyses of the test intercorrelations for each group revealed more factorial invariance across the IQ groups than had been suggested by a previous exploratory study. It was concluded that strong individual differences exist in simultaneous and successive syntheses over the major portion of the standardized intelligence range, and no high degree of specialization of information processing was characteristic of an intelligence group.     

Stimulus- and pellet-induced drinking during a successive discrimination

In three experiments, interim water drinking was examined in rats exposed to a multiple schedule whose two components were extinction and a variable-time 30-s schedule of food delivery. Two different drinking patterns were observed in Experiment 1. Pellet-induced drinking, characterized by high rates of postpellet drinking in the variable-time component, with little or no drinking in extinction, occurred when the acquisition of stable postpellet drinking preceded discrimination training. Stimulus-induced drinking, characterized by a burst of drinking at the onset of extinction, with no drinking during the variable-time schedule, occurred when discrimination training preceded all other experimental conditions. With extended training, stimulus-induced drinking eventually was accompanied by postpellet drinking. In Experiment 2, the rate of stimulus-induced drinking and the number of sessions during which it occurred without postpellet drinking were found to be inversely related to component duration. In Experiment 3, the rate of schedule-induced drinking was found to vary directly with component duration.     

Visual recognition under conditions of high and low discrimination redundancy

The purpose of this investigation was to measure the minimum interval for recognition under conditions of high and low discrimination redundancy. The minimum interval for recognition is the briefest interval between two stimuli at which the first stimulus can be processed. Two sets of four digits were used. Digits were selected so that one set exhibited high discrimination redundancy and the other low discrimination redundancy. Ten Ss viewed digits with high discrimination redundancy, and 10 Ss viewed digits with low discrimination redundancy. The minimum interval for recognition for Ss tested with high discrimination redundancy was nearly twice as large as the minimum interval for recognition of the digits with low discrimination redundancy.     

Simultaneous and successive syntheses and linguistic processes1

The present study investigated the relationships between simultaneous and successive modes of cognitive processing and performance on word association, ambiguities and class inclusion tasks in a sample of 60 grade three children. Simultaneous processing was significantly related to class inclusion performance and to comprehension of lexical ambiguities. There was also some evidence of a relationship between paradigmatic responding on the word association task and simultaneous processing. Successive processing was significantly related to surface structure and underlying structure ambiguities and was also involved in class inclusion performance. These results are consistent with hypotheses derived from the neurolinguistic theories of Luria and Jakobson.     

Stimulus comparison strategies and task demands in successive discrimination

This research isolates two distinct strategies used to identify stimuli presented at different rates in successive discrimination tasks. The short-term strategy (used at rapid rates) compares current stimuli to immediately prior stimuli present in sensory or other short-term storage, whereas the long-term strategy (used at slow rates) compares current stimuli to a standard stimulus in long-term memory. In Experiment 1, subjects detected a medium-duration tone amid both long and short distractors. Analysis of false alarms indicated that strategy choice is strongly influenced by event rate, and therefore by the presence or absence of sensory traces of preceding stimuli. Experiment 2 was designed to force subjects to use the short-term strategy (to detect targets, present stimuli had to be compared to their immediate predecessors), and varied the event rate. Subjects were able to maintain a high level of performance throughout the task only at the fastest event rate. This pattern of results suggested that when the task demanded it, subjects could use a particular strategy, but if the event rate (and consequently the availability or otherwise of relevant memorial traces) was not favourable to that strategy, then performance was disadvantaged.     

Simultaneous auditory discrimination.

Stimuli in many visual stimulus control studies typically are presented simultaneously; in contrast the stimuli in auditory discrimination studies are presented successively. Many everyday auditory stimuli that control responding occur simultaneously. This suggests that simultaneous auditory discriminations should be readily acquired. The purpose of the present experiment was to train rats in a simultaneous auditory discrimination. The apparatus consisted of a cage with two response levers mounted on one wall and a speaker mounted adjacent to each lever. A feeder was mounted on the opposite wall. In a go-right/go-left procedure, two stimuli were presented on each trial, a wide-band noise burst through one speaker and a 2-kHz complex signal through the other. The stimuli alternated randomly from side to side across trials, and the stimulus correlated with reinforcement for presses varied across subjects. The rats acquired the discrimination in 400 to 700 trials, and no response position preference developed during acquisition. The ease with which the simultaneous discrimination was acquired suggests that procedures, such as matching to sample, that require simultaneous presentation of stimuli can be used with auditory stimuli in animals having poor vision.     

Diazepam-induced impairment of a go-no go successive discrimination

Diazepam (2.0 and 4.0 mg/kg, but not 1.0 mg/kg) administered in eight acquisition sessions significantly impaired the light-cued successive discrimination of male Sprague-Dawley rats. In two postdrug (vehicle) sessions, groups previously treated with the drug demonstrated good recovery in discrimination. An analysis of response components indicated that the impairment was due to the failure of drugged subjects to inhibit or withhold responses during the no go periods of the task. These findings are consistent with a "disinhibitory hypothesis" of drug impairment. The similarity of the present findings to those previously reported with chlordiazepoxide suggests that such effects are a generalized characteristic of the benzodiazepine class of drugs.