The effect of interpolated activity on a treble right-left alternation task

In a delayed treble alternation task the number of errors made by human subjects was found to increase when an irrelevant task was presented in the delay interval. The number of errors increased with the number of items presented in the delay interval, but neither the difficulty of the irrelevant task nor its similarity to the alternation task was found to affect the number of errors.     

Inescapable shock and attention to internal versus external cues in a water discrimination escape task

In these experiments we examined discrimination learning in a water escape task following exposure to escapable, yoked inescapable, or no electric shock. Inescapable shock did not have an effect on swim speeds in any of the experiments. Inescapable shock interfered with the acquisition of a position (left-right) discrimination when an irrelevant brightness cue (black and white stimuli) was present. However, inescapable shock did not affect the acquisition of the position discrimination when the irrelevant brightness cue was removed. Inescapably shocked subjects showed facilitated learning relative to escapably shocked and nonshocked subjects when the brightness cue was included as a relevant cue. These data may resolve discrepancies between studies that did, and did not, find inescapable shock to interfere with the acquisition of discriminations. Moreover, they point to attentional processes as one locus of the cognitive changes produced by inescapable shock and suggest that exposure to inescapable shock biases attention away from "internal" response-related cues toward "external" cues.     

Effects of task difficulty on subsequent preference for visual complexity.

Ss rated on a 1 to 13 Likert scale their preference for four environmental scenes which differed in complexity. Ss were then given 30 sec. to solve each of 10 3-, 5-, or 7-letter single-solution anagrams. Finally the Ss rated four new slides which were of the same complexity level as the slides seen during the first session. Change scores were calculated by subtracting the preference ratings at each complexity level during the first session from the rating at the corresponding complexity level during the second session. The Anagram Complexity X Slide Complexity interaction was significant: the complexity of the slides showing the most positive change scores was inversely related to the complexity of the anagrams attempted. The results were discussed in terms of optimal level of stimulation theories.     

Retention interval and intertrial interval in a serial learning or delayed discrimination task

In each of four experiments, rats were provided with the same three-event decreasing series (18-1-0) of 0.045-g food pellets in a runway. Tracking, running fast to 18 pellets and running slow to 1 and 0 pellets, was investigated as a function of the temporal interval elapsing between the events of the series (the retention interval), shifts in retention interval, and number of trials each day (or the intertrial interval), a trial being defined as presentation of each of the three events of the series. Neither retention interval, which varied from 15 s to 30 min in various investigations, nor shifts in retention interval affected tracking when only one trial was given each day. But when more than one daily trial was given, tracking was acquired more slowly and was disrupted by a shift in retention interval from 15 s to 5 min. Tracking was also disrupted by a shift from one to two trials each day. These results indicate that when given one 18-1-0 trial each day, the rat partitions events on a first-event/subsequent-event basis; that little forgetting occurs even at long retention intervals; that somewhat different memories signal events when one or more than one 18-1-0 trial occurs each day; and that retention interval deficits can arise owing to the same or similar memories' signaling different events. The results described limit the generality of three hypotheses suggested in two recent investigations: that as retention interval increases, rats find it increasingly difficult to remember and utilize serial position cues; that tracking in serial tasks is not influenced by number of trials each day; and that there are specific stimuli associated with each retention interval which, when changed, necessarily disrupt performance.     

Empirical and clinical assessments of children's object relations and object representations.

A series of investigations that assess children's object representations using the Rorschach Mutuality of Autonomy (MOA) Scale are reviewed. The scale is viewed as a summary measure of a child's repertoire of previous interpersonal interactions. It has been effective in delineating qualitative aspects of a number of child psychopathological syndromes, in documenting short-term object representational shifts in children undergoing surgery, and in foretelling key paradigms in child psychotherapy. This effectiveness provides empirical support for the hypothesized salience of object representations as an integral facet of personality and affirms Escalona's (1968) contention that capturing a child's phenomenological experience enhances our capacity to predict later outcome.     

Effects of alternating set for speed or accuracy on response time,accuracy and confidence in a unidimensional discrimination task

Three approaches to a theoretical analysis of confidence judgments are considered: one linking confidence to the number of sensory observations, one based on a distinction between ‘state’ and ‘process’ factors, and a ‘balance of evidence’ hypothesis developed from an accumulator model of discrimination. An experiment is described in which observers were asked to decide which of two parallel lines was the longer, and to rate their confidence in each judgment. Each observer's set for speed or accuracy was manipulated over successive blocks of trials, and effects on response time, accuracy, and confidence were examined. Under an accuracy set, observers produced a higher percentage of correct responses, had longer response times, and made more confident judgments than under a set for speed. Within both speed and accuracy blocks, however, confidence ratings were inversely related to response time. The data on response accuracy, time, and confidence indicate certain deficiencies in either of the first two approaches, but were well accounted for by the third.     

Reaction times of pigeons on a wavelength discrimination task

After extensive pretraining, three pigeons were exposed in 2-second trials to a random series of 14 light wavelengths, ranging in one nanometer (nm) steps from 575 nanometers to 589 nanometers. Responses to one of the wavelengths, 582 nanometers, were intermittently reinforced. The relative frequency of response approached 1.0 at 582 nanometers, and decreased with progressively higher and lower wavelengths. Reaction times shorter than about 0.2 second occurred with a low frequency that was largely independent of wavelength. Wavelength controlled the frequency of longer reaction times, but did not affect the distribution of these reaction times. Consequently, receiver-operating characteristic curves constructed by using reaction time as a rating measure did not conform to the signal-detection model, in contrast to such conformity when response rate is used in a similar way. The data suggest that stimulus onset as such triggers early response emission with some small probability; the probability of responses with longer latency is controlled by wavelength, but their time of emission is controlled by some independent process.     

Children's understanding of class inclusion hierarchies: the relationship between external representation and task performance

Three experiments were designed to investigate children's understanding of class inclusion hierarchies and to determine whether such understanding may be related to children's ability to construct external representations for information that was hierarchical in nature. Understanding of hierarchies was studied through tasks designed to demonstrate children's ability with subset/superset classification and knowledge of asymmetric and transitive relations. Children were asked to construct their own external representations for passages containing information that could be represented hierarchically. It was hypothesized that the quality of children's external representations would be related to their ability to respond to questions related to the passages. Children's responses to questions, as well as their external representations, suggested that children as young as second grade have substantial understanding of hierarchical relations. Although the external representations were constructed in drawing, written, or structured modes, the data revealed a strong relationship between the quality of children's external representations and their performance on question tasks requiring both recognition and reasoning. Finally, children understood the relationships expressed in tree diagrams and could construct such diagrams to respond to questions. Implications of the findings, particularly as related to note-taking skills, and suggestions for further research are discussed.     

Nifedipine blocks retention of a visual discrimination task in chicks.

Reports that the dihydropyridine Ca2+ channel antagonists may facilitate memory led to the present study of the behavioral effects of nifedipine. Ninety-two 4-day-old male chicks received 0, 100 nM, 100 microM, or 10 mM nifedipine. Drugs were administered in volumes of 2 microliters into the fourth cerebral ventricle 5 min before training on a visual discrimination task. Nifedipine did not produce any detectable changes in behavior during acquisition trials. Retention, however, was impaired 24 h after training in the 100 nM and 100 microM nifedipine-treated chicks, which made significantly more errors than controls. Nifedipine did not affect the amount of time required to complete the task. No effects on body weight gain were detected, suggesting that the memory impairment was not due to a change in feeding behavior. These data are discussed in terms of the role of calcium-dependent processes in memory.     

An inexpensive and automated method for presenting olfactory or tactile stimuli to rats in a two-choice discrimination task

An inexpensive and automated method for presentation of olfactory or tactile stimuli in a two-choice task for rats was implemented with the use of a computer-controlled bidirectional motor. The motor rotated a disk that presented two stimuli of different texture for tactile discrimination, or different odor for olfactory discrimination. Because the solid olfactory stimuli were placed outside the chamber in metal pods with a mesh at front for odor sampling, "washout" of odors between trials was not necessary. To avoid differential auditory cues from motor rotation, the stimuli were arranged such that on each trial the motor always rotated exactly one quarter revolution (in 1 s), left or right, to present the next stimulus at trial start. To illustrate the use of the equipment, 2 rats were trained on tactile discrimination and 2 rats on olfactory discrimination. The rats sampled the stimulus on the disk through a port on the back wall by sniffing at it (olfactory) or touching it (tactile). The task was a go-left/go-right discrimination with the stimulus on the disk being discriminative for which lever provided reinforcement. The rats reached a stable level above 90% correct after 21 and 32 training sessions for tactile and olfactory discrimination, respectively. The article outlines how the equipment was constructed from low-cost components. Inputs from and outputs to the equipment were implemented through the parallel port of a personal computer without the use of a commercial interface board. The method of automated and low-cost presentation of olfactory or tactile stimuli should be of use for a variety of experimental situations such as matching-to-sample and cross-modal discrimination.     

Performance of rats on a discrimination operant alley task discriminated

An automated discriminated operant alley apparatus is described. Data from four rat strains indicate that the light-dark choice is learned by both pigmented and albino rats. The task requires a minimum of experimenter time and allows initial acquisition to be recorded without the interference of a shaping procedure.     

The role of the human medial temporal lobe in object recognition and object discrimination.

This paper reviews evidence from neuropsychological patient studies relevant to two questions concerning the functions of the medial temporal lobe in humans. The first is whether the hippocampus and the adjacent perirhinal cortex make different contributions to memory. Data are discussed from two patients with adult-onset bilateral hippocampal damage who show a sparing of item recognition relative to recall and certain types of associative recognition. It is argued that these data are consistent with Aggleton and Brown's (1999) proposal that familiarity-based recognition memory is not dependent on the hippocampus but is mediated by the perirhinal cortex and dorso-medial thalamic nucleus. The second question is whether the recognition memory deficit observed in medial temporal lobe amnesia can be explained by a deficit in perceptual processing and representation of objects rather than a deficit in memory per se. The finding that amnesics were impaired at recognizing, after short delays, patterns that they could successfully discriminate suggests that their memory impairment did not result from an object-processing deficit. The possibility remains, however, that the human perirhinal cortex plays a role in object processing, as well as in recognition memory, and data are presented that support this possibility.     

Lesions of the dorsolateral or dorsomedial striatum impair performance of a previously acquired simple discrimination task

Previous evidence has suggested a specific role for the dorsal striatum, especially the dorsolateral region of the dorsal striatum, in stimulus-response learning. In a previous study, we found an impairment in animals with dorsolateral striatal lesions on a simple discrimination task (CS+/CS-), thought to require the involvement of both stimulus-reward and stimulus-response learning. It is possible that the generally poor performance of dorsolateral lesioned animals on this experiment precluded adequate exposure to stimulus-reward pairings necessary for solving this task, and, thus, had little to do with stimulus-response learning. To test this hypothesis, the performance of animals with dorsolateral and dorsomedial striatal lesions was assessed on a previously acquired simple discrimination task. To independently assess the effects of each lesion on the performance of stimulus-reward learning, dorsolateral and dorsomedial lesioned animals were assessed on a previously acquired conditioned place preference task (CPP). In agreement with our earlier experiment, and the stimulus-response interpretation of dorsolateral striatal function, animals with dorsolateral striatal lesions were found to be impaired during post-lesion performance of the simple discrimination task, but not CPP learning. Additionally, dorsomedial lesioned animals were found to be impaired in performance of the simple discrimination task, but not on the CPP task. Possible explanations for the differences between the role of the dorsomedial striatum in acquisition and expression of the simple discrimination task are proposed.     

Influences of lateral preference and personality on behaviour towards a manual sorting task

Differences in task behaviour between left- and right-handers and left- and right-eared individuals have been reported (e.g.  and ) with left-handers taking longer to begin a task and right-eared individuals having a more disinhibited approach. Personality measurements are also important when examining approach behaviour. Jackson (2008) reported that those with higher neuroticism levels and a right-ear preference react faster to tasks. The current study investigated the effects of lateral preference and personality on behaviour towards a manual sorting task. Eighty-five participants completed laterality and personality scales and a card-sorting task. Degree of hand preference was found to influence behaviour towards the task with strong left-handers taking longer to begin. Those with a left congruent lateral preference (left-hand, left-ear) took significantly longer to begin the task than those with a right congruent preference. Neither neuroticism nor extraversion influenced task approach. We concluded that hand preference, and more specifically a strong left-hand preference is a good predictor of a longer initiation time on a manual task. Ear preference on its own does not predict initiation time.