Memory and attention in combat-related post-traumatic stress disorder (PTSD)

Vietnam combat veterans assigned diagnoses of PTSD were compared on measures of attention/concentration, new learning, and memory with Army National Guard enlistees who reported no unusual traumatic events or stress-related symptoms. Results showed that PTSD veterans performed more poorly than the comparison sample on a measure of verbal learning, exhibiting less proficient cumulative acquisition across repeated exposures, greater sensitivity to proactive interference, and more perseverative errors. Veterans with PTSD diagnoses also evidenced impairments in word fluency and visual attention/tracking abilities. These preliminary findings suggest that diagnoses of chronic PTSD in combat veterans are associated with cognitive performance deficits, when comparisons are made with military troops judged to be free of stress-related psychopathology. Results are consistent with self-reported complaints of concentration and memory impairments among PTSD-diagnosed clinical samples, thus highlighting the need for continued investigation of the neuropsychologlcal sequelae of prolonged stress exposure.     

Alcohol-related knowledge and attitudes in people with a mild learning disability – the effects of a ‘sensible drinking’ group

Alcohol-related knowledge and attitudes in people with a mild learning disability, who were either living, or being prepared to live, in relatively independent conditions in the community, were assessed through a structured interview format. Compared with non-learning-disabled teenagers, adults and a hospitalized patient sample, alcohol-related knowledge in the people with a learning disability was found to be significantly poorer, alcohol was reported as having particularly negative effects and susceptibility to social pressure to drink alcohol was greater. A ‘sensible drinking’ group, taking a social skills and influences approach to alcohol education, was conducted with a subgroup of the individuals with a learning disability. The group format and methods, including in vivo sessions in a public house, are described. Follow-up evaluations suggested some significant positive changes in knowledge, attitudes and sensible drinking skills. It is concluded that this population, which is increasingly living, or being moved into, independent conditions in the community, is at least as vulnerable to social influences on alcohol use and abuse as are young people. As with young people, the usefulness of making available such alcohol-education programmes as described in this study, is discussed.     

内隐学习“三高”特征的实验研究

本研究在社会认知的人物特征识别范畴内,探讨在高强度练习和准确反馈条件下,内隐学习的高选择力、高潜力以及高密度贮存三大特征。实验采用一种测量内隐和外显学习的新方法,要求被试学会把像片按其组合特征分类。这些特征包括人物姿势的正侧面(显著维度特征),人物容貌的美丑(非显著维度特征)。结果表明:(1)非显著特征的学习,内隐被试表现出更大且显著的底层规则的迁移,比外显被试具有更高的选择力。(2)内隐被试表现出高潜力的内隐知识。(3)信息论处理揭示了内隐知识传递和贮存的高密性和高效性。     

A comparison of self-instructional checking procedures for remediating mathematical deficits

We examined the relative effectiveness of three procedures for teaching long multiplication/division to seven adolescents with learning disabilities: no-checking, end-checking, and multi-checking. During training, each subject was taught by modelling and imitation to verbalize self-instructions in the form of a strategy while solving the problems. The relative effects of the checking and no-checking procedures on accuracy and rate of problems completed were examined in an alternating treatments design. The best treatment was then given alone and a reversal was implemented six weeks later, followed by a return to the best treatment during a final phase. Irrespective of the procedure used, the subjects' accuracy improved while the rate of problems completed decreased. These effects were greatest with the multi-checking procedure for six of the seven subjects. Generalization to untaught problems of various levels of complexity occurred under all procedures. Though maintenance effects were seen during the follow-up, accuracy was generally higher and more reliable when the subject's best checking procedure was reinstated. It is suggested that error detection and correction were important for maintaining high levels of accuracy and that these operated differentially in the three procedures to produce the differing levels of accuracy. The role of other factors such as pre-skill knowledge, complexity of the problem and prior reinforcement history are also considered.     

Teaching a chained task with a simultaneous prompting procedure

Simultaneous prompting, a type of antecedent prompt and test procedure, was used to teach the chained task of making juice from a frozen concentrate using a pictorial recipe to four elementary-aged students with moderate intellectual disabilities. Using a multiple probe design, all students acquired the task and maintained the behavior with at least 85% accuracy up to 60 days after training was terminated. In addition, students generalized the skill across settings and materials. The students' ability to expressively identify the words shown on the recipe cards was tested prior to and after training. Although not directly trained, three of the four students increased their ability to read the words.     

Deafness and mother–child interaction: Scaffolded instruction and the learning of problem-solving skills

This study examines the effects of maternal teaching style on the developing problem-solving abilities of deaf and hearing pre-school children. Mothers and children from three matched groups, hearing mother-deaf child, hearing mother-hearing child, and deaf mother-deaf child, were videotaped while the mother instructed the child on a block construction task and again when the child attempted the task independently. Dependent measures were maternal instructional style and child performance. The mothers in the deaf mother-deaf child and hearing mother-hearing child dyads used appropriate scaffolding behaviour and their children were more likely to exhibit adept and independent problem-solving abilities than the deaf children of hearing mothers. The findings of this study support Vygotsky's notion of the ‘zone of proximal development’ and the concept of adult scaffolding of children's learning.     

Transient effects of acquisition history on generalization in a matching-to-sample task

This study examined the role of learning history on the acquisition of a matching-to-sample task. Twelve preschool children learned four stimulus classes through instructions, shaping, or imitation. After reaching criterion, the subjects were exposed to changed discrimination contingencies to determine how each learning history affected the acquisition of responses appropriate to the new contingencies. All subjects reached criterion on the new relations, although the subjects with a shaping history adapted slightly more quickly than those subjects with a history of instructions or imitation. Given sufficient exposure to changed contingencies, rule-driven insensitivity to contingencies was overcome by experience with consequences. This result may be specific to younger subjects, but it suggests that instructions can be used in education without creating insensitivity to contingencies.     

Substitutability between conditioned and primary reinforcers in discrimination acquisition.

Rats and pigeons were trained on a series of reversals of a conditional simultaneous discrimination. The percentage of reinforcement for correct trials was varied across reversals. When nonreinforced correct trials produced the same feedback as incorrect trials, the number of errors to reach an acquisition criterion was greater for smaller percentages of reinforcement, but the number of reinforcers required was either approximately constant or smaller for the smaller percentages. When a stimulus paired with food (the conditioned reinforcer) was added on nonreinforced correct trials, both measures were substantially decreased. When the same stimulus was presented, but without a history of food pairing, learning rate was similar to when no stimulus was presented on nonreinforced trials. The results provide direct evidence that conditioned reinforcers may substitute, although imperfectly, for a primary reinforcer, and that pairing with the primary reinforcer is a necessary condition for such substitutability to occur.     

Stimulus generalization, discrimination learning, and peak shift in horses.

Using horses, we investigated three aspects of the stimulus control of lever-pressing behavior: stimulus generalization, discrimination learning, and peak shift. Nine solid black circles, ranging in size from 0.5 in. to 4.5 in. (1.3 cm to 11.4 cm) served as stimuli. Each horse was shaped, using successive approximations, to press a rat lever with its lip in the presence of a positive stimulus, the 2.5-in. (6.4-cm) circle. Shaping proceeded quickly and was comparable to that of other laboratory organisms. After responding was maintained on a variable-interval 30-s schedule, stimulus generalization gradients were collected from 2 horses prior to discrimination training. During discrimination training, grain followed lever presses in the presence of a positive stimulus (a 2.5-in circle) and never followed lever presses in the presence of a negative stimulus (a 1.5-in. [3.8-cm] circle). Three horses met a criterion of zero responses to the negative stimulus in fewer than 15 sessions. Horses given stimulus generalization testing prior to discrimination training produced symmetrical gradients; horses given discrimination training prior to generalization testing produced asymmetrical gradients. The peak of these gradients shifted away from the negative stimulus. These results are consistent with discrimination, stimulus generalization, and peak-shift phenomena observed in other organisms.     

Choice with probabilistic reinforcement: effects of delay and conditioned reinforcers.

Two experiments measured pigeons' choices between probabilistic reinforcers and certain but delayed reinforcers. In Experiment 1, a peck on a red key led to a 5-s delay and then a possible reinforcer (with a probability of .2). A peck on a green key led to a certain reinforcer after an adjusting delay. This delay was adjusted over trials so as to estimate an indifference point, or a duration at which the two alternatives were chosen about equally often. In all conditions, red houselights were present during the 5-s delay on reinforced trials with the probabilistic alternative, but the houselight colors on nonreinforced trials differed across conditions. Subjects showed a stronger preference for the probabilistic alternative when the houselights were a different color (white or blue) during the delay on nonreinforced trials than when they were red on both reinforced and nonreinforced trials. These results supported the hypothesis that the value or effectiveness of a probabilistic reinforcer is inversely related to the cumulative time per reinforcer spent in the presence of stimuli associated with the probabilistic alternative. Experiment 2 tested some quantitative versions of this hypothesis by varying the delay for the probabilistic alternative (either 0 s or 2 s) and the probability of reinforcement (from .1 to 1.0). The results were best described by an equation that took into account both the cumulative durations of stimuli associated with the probabilistic reinforcer and the variability in these durations from one reinforcer to the next.