DO INFANTS SHOW GENERALIZED IMITATION OF GESTURES? II. THE EFFECTS OF SKILLS TRAINING AND MULTIPLE EXEMPLAR MATCHING TRAINING

The determinants of generalized imitation of manual gestures were investigated in 1‐ to 2‐year‐old infants. Eleven infants were first trained eight baseline matching relations; then, four novel gestures that the infants did not match in probe trials were selected as target behaviors. Next, in a generalized imitation test in which matching responses to baseline models were intermittently reinforced, but matching responses to target models were not eligible for reinforcement, the infants matched baseline models but not the majority of their target behaviors. To ensure their failure to match the target behaviors was not due to motor constraints, the infants were trained, in a multiple‐baseline procedure, to produce the target responses under stimulus control that did not include an antecedent model of the target behavior. There was no evidence of generalized imitation in subsequent tests. When the infants were next trained to match each target behavior to criterion (tested in extinction) in a multiple‐baseline‐across‐behaviors procedure, only 2 infants continued to match all their targets in subsequent tests; the remaining infants matched only some of them. Seven infants were next given mixed matching training with the target behaviors to criterion (tested in extinction); they subsequently matched these targets without reinforcement when interspersed with trials on which matching responses to baseline models were intermittently reinforced. In repeat tests, administered at 3‐week intervals, these 7 children (and 2 that did not take part in mixed matching training) continued to match most of their target behaviors. The results support a trained matching account, but provide no evidence of generalized imitation, in 1‐ to 2‐year‐old infants.     

Is there still a cognitive cost of being a twin in the UK?

ObjectiveTo investigate whether twins still perform below singletons in cognitive ability tests and in national educational attainment examinations in a recent UK cohort of 11-year-olds.DesignPopulation-based cohort study, using a validated method of twin extraction.SettingEnglish state schools.Participants178,599 pupils (mean age 11 years) attending English state schools in 2004, representing 93% of local educational authorities.Main outcome measuresVerbal, quantitative and nonverbal reasoning measured by the Cognitive Abilities Test — Third Edition (CAT3), and educational attainment in English, maths and science from Key Stage 2 national curriculum tests.ResultsTwin-singleton differences in cognitive ability were of negligible effect size. Mean performance of twins was 1% of a SD below singletons on general cognitive ability, 3% lower on verbal reasoning, and less than 1% of a SD lower on quantitative and nonverbal reasoning, with and without adjustment for sex. Almost identical proportions of twins and singletons attained the expected standards of educational performance in English (80.4% versus 80.5%, respectively), maths (77.4% versus 77.3%), and science (90.1% versus 88.8%). There were no differences in rates of twins and singletons achieving higher or lower performance levels.ConclusionThe cognitive cost of being a twin reported in previous cohorts of UK children no longer exists in a large, contemporary and population-representative sample.     

Larger brain and white matter volumes in children with developmental language disorder

Developmental language disorder (DLD) is predominantly a language disorder, but children with DLD also manifest non-language impairments, and neuroanatomical abnormalities have been found in multiple areas of the brain, not all language-associated. We therefore performed a whole brain general segmentation analysis of all major brain regions on MRI scans of 24 DLD subjects (16M, 8F) and 30 controls (15M, 15F), ages 5.7 to 11.3 years. Children with DLD showed increased total brain volume, driven predominantly by a substantial increase in the volume of cerebral white matter. Cerebral cortex and caudate were relatively but not absolutely smaller in DLD. These findings are discussed in relation to issues of specificity vs. generality as they arise in debates about (1) modular vs. general processing deficits and connectionist modeling in DLD, (2) language-specific vs. pervasive, non-specific deficits in DLD and (3) specificity of the disorder vs. overlap with other disorders, notably autism.     

A respectable job: Factors which influence young Asians' choice of career

To find out why some college or university courses are particularly attractive to ethnic-minority school-leavers, school pupils and first-year students of South Asian (n=158) and UK origin (n = 158) completed a questionnaire relating to occupational choice. The social position attainable from a 'respected' profession and the ability to work with others who share similar beliefs were found to be of greater importance to subjects from an Asian background than to those of UK origin, who placed greater emphasis on personal growth and autonomy. There was no evidence that the Asian young people were consciously choosing careers with the aim of avoiding discrimination.     

Effects of counselor sex,student sex,and student attractiveness on counselors' judgments

Thirty-two male and thirty-two female high school counselors in a large metropolitan school district were provided with routine student profile data and asked to make predictions about the student's potential for post-high school education and to suggest occupations for the student to explore. All data reviewed by the counselors were identical except for a photograph of the student attached to the profile. Within counselor sex groups, counselors were randomly assigned to one of the following four photograph conditions: (a) attractive female; (b) unattractive female; (c) attractive male; and (d) unattractive male. Male subjects were found to discriminate on the basis of student sex when they suggested occupations for the student to explore. Predictions of post-high school education and the social status of suggested occupations were not found to be related to counselor sex, student sex, or student attractiveness.     

Topography of signal-centered behavior in the rat: Effects of deprivation state and reinforcer type

In a series of three experiments, groups of food-deprived and water-deprived rats were given pairings of a retractable lever (CS⁺) with response-independent deliveries of either solid or liquid reinforcers. In Experiment 1 food-deprived rats given a solid-pellet reinforcer differentially tended to sniff, paw, mouth, and bite the CS⁺ lever more often than a lever that was not paired with food (CS⁻), whereas food-deprived rats given a liquid reinforcer tended to differentially sniff, paw, and lick the CS⁺ lever. 23½-hour water-deprived rats given liquid reinforcers showed very little CS⁺ contact. In Experiment 2 increasing the severity of water deprivation from 23½ to 47½ hours significantly increased CS⁺ contact. In Experiment 3, subjects that were simultaneously food and water deprived and given a water reinforcer failed to exhibit differential CS⁺ contact, but subjects that were simultaneously food and water deprived and given a food reinforcer did acquire differential CS⁺-contact behavior. These results suggest that (a) even under a single motivational state the nature of signal-centered behavior can be determined by type of reinforcer, (b) although water reinforcement produces less signal contact than food reinforcement, this can be facilitated with more severe water-deprivation levels, and (c) high CS-contact rates using food reinforcement are not simply a product of reductions in body weight with food deprivation.     

Reevaluating evaluative conditioning: a nonassociative explanation of conditioning effects in the visual evaluative conditioning paradigm.

In 2 studies, the authors investigated whether evaluative conditioning (EC) is an associative phenomenon. Experiment 1 compared a standard EC paradigm with nonpaired and no-treatment control conditions. EC effects were obtained only when the conditioned stimulus (CS) and unconditioned stimulus (UCS) were rated as perceptually similar. However, similar EC effects were obtained in both control groups. An earlier failure to obtain EC effects was reanalyzed in Experiment 2. Conditioning-like effects were found when comparing a CS with the most perceptually similar UCSs used in the procedure but not when analyzing a CS rating with respect to the UCS with which it was paired during conditioning. The implications are that EC effects found in many studies are not due to associative learning and that the special characteristics of EC (conditioning without awareness and resistance to extinction) are probably nonassociative artifacts of the EC paradigm.     

Effects of reinforcement magnitude on interval and ratio schedules

Rats' lever pressing was studied on three schedules of reinforcement: fixed interval, response-initiated fixed interval, and fixed ratio. In testing, concentration of the milk reinforcer was varied within each session. On all schedules, duration of the postreinforcement pause was an increasing function of the concentration of the preceding reinforcer. The running rate (response rate calculated by excluding the postreinforcement pauses) increased linearly as a function of the preceding magnitude of reinforcement on fixed interval, showed slight increases for two of the three animals on response-initiated fixed interval, and did not change systematically on fixed ratio. In all cases, the overall response rate either declined or showed no effect of concentration. The major effect of increasing the reinforcement magnitude was in determining the duration of the following postreinforcement pause, and changes in the response rate reflected this main effect.