Anatomic Magnetic Resonance Imaging of the Developing Child and Adolescent Brain and Effects of Genetic Variation

Magnetic resonance imaging studies have begun to map effects of genetic variation on trajectories of brain development. Longitudinal studies of children and adolescents demonstrate a general pattern of childhood peaks of gray matter followed by adolescent declines, functional and structural increases in connectivity and integrative processing, and a changing balance between limbic/subcortical and frontal lobe functions, which extends well into young adulthood. Twin studies have demonstrated that genetic factors are responsible for a significant amount of variation in pediatric brain morphometry. Longitudinal studies have shown specific genetic polymorphisms affect rates of cortical changes associated with maturation. Although over-interpretation and premature application of neuroimaging findings for diagnostic purposes remains a risk, converging data from multiple imaging modalities is beginning to elucidate the influences of genetic factors on brain development and implications of maturational changes for cognition, emotion, and behavior.     

The tooth,the whole tooth and nothing but the tooth: how belief in the Tooth Fairy can engender false memories

To examine how children's fantasy beliefs can affect memory for their experiences, 5‐ and 6‐year‐olds with differing levels of belief in the reality of the Tooth Fairy were prompted to recall their most recent primary tooth loss in either a truthful or fun manner. Many of the children who fully believed in the existence of the Tooth Fairy reported supernatural experiences consistent with the myth under both sets of recall instructions, whereas those who realized the fictionality of the myth recalled mainly realistic experiences. However, those children with equivocal beliefs evidenced a different pattern under each set of instructions, recalling mainly realistic experiences when asked to be truthful and reporting many fantastical experiences when prompted to relate the tooth loss in a fun manner. These findings suggest that children's beliefs in the reality of fantastic phenomena can give rise to genuine constructive memory errors in line with their fantasies. Copyright © 2007 John Wiley & Sons, Ltd.     

Resurgence Following Higher or Lower Quality Alternative Reinforcement

Resurgence is a temporary increase in a previously suppressed target behavior following a worsening in reinforcement conditions. Previous studies have examined how higher rates or magnitudes of alternative reinforcement affect suppression of the target behavior and subsequent resurgence. However, there has been no investigation of the effects of higher versus lower qualities of alternative reinforcement on resurgence. Using a three-phase resurgence preparation with rats, the present experiments examined the effects of an alternative reinforcer that was of higher (Experiment 1) or lower (Experiment 2) quality than the reinforcer that had previously maintained the target behavior. The results of both experiments showed greater reductions in target behavior with a higher quality alternative reinforcer and larger increases in target responding when a higher quality alternative reinforcer was removed. Along with prior findings with higher rates and magnitudes of alternative reinforcement, these findings suggest that variations in reinforcer dimensions that increase the efficacy of alternative reinforcement also tend to increase resurgence when alternative reinforcement is removed. The results are discussed in terms of the resurgence as choice in context model and in terms of potential clinical implications.     

Generalization of learning from picture books to novel test conditions by 18- and 24-month-old children

Researchers know little about whether very young children can recognize objects originally introduced to them in a picture book when they encounter similar looking objects in various real-world contexts. The present studies used an imitation procedure to explore young children's ability to generalize a novel action sequence from a picture book to novel test conditions. The authors found that 18-month-olds imitated the action sequence from a book only when the conditions at testing matched those at encoding; altering the test stimuli or context disrupted imitation (Experiment 1A). In contrast, the 24-month-olds imitated the action sequence with changes to both the test context and stimuli (Experiment 1B). Moreover, although the 24-month-olds exhibited deferred imitation with no changes to the test conditions, they did not defer imitation with changes to the context and stimuli (Experiment 2). Two factors may account for the pattern of results: age-related changes in children's ability to utilize novel retrieval cues as well as their emerging ability to understand the representational nature of pictures.     

Comparison of Single Unit Responses to Tone, Light, and Compound Conditioned Stimuli during Rabbit Classical Eyeblink Conditioning

Unit recordings and lesion studies have implicated the cerebellum as an essential site for the acquisition and maintenance of the conditioned eyeblink response. The current study looked at the neural characteristics of conditioned stimulus (CS) processing in the interpositus nucleus of the cerebellum after training New Zealand white rabbits (Oryctolagus cuniculus) in one of two conditioning paradigms: (a) compound conditioning (CMP), a compound CS consisting of light and tone paired with an air puff unconditioned stimulus (US); or (b) stimulus compounding (ALT), alternating blocks of tone CS and light CS trials paired with the air puff US. Single unit responses were recorded during five sessions after the animals had reached an asymptotic level of responding. Animals were tested for behavioral and neural responses to CS alone trials that included tone alone, light alone, and compound tone-light trials. For the CMP group, the compound CS elicited 80 to 90% conditioned eyeblink responses (CRs), whereas the individual tone and light CSs elicited only 40 to 50% CRs. For the ALT group, all three CSs (tone, light, and compound) elicited very high levels of responding of at least 80% CRs. For the CMP group, there were roughly equal numbers of cells responding to all of the CSs. This includes cells that responded exclusively to one, and only one, of the three stimuli and also those cells that responded to combinations of two or more. Cells from the ALT group were far more likely to respond exclusively to only one of the CSs. Both the behavioral and physiological results suggest that the compound tone-light stimulus was processed as a distinct stimulus, separate from the component tone and light. These results are discussed in the context of multisensory processing.     

Medical students' and residents' gender bias in the diagnosis, treatment, and interpretation of coronary heart disease symptoms.

Two competing hypotheses explaining gender bias in cardiac care were tested. The first posits that women's coronary heart disease (CHD) symptoms are simply misinterpreted or discounted. The second posits that women's CHD symptoms are misinterpreted when presented in the context of stress. In two studies, medical students and residents randomized to 2 (male vs. female) x 2 (stress vs. nostress) experiments read vignettes of patients with CHD symptoms and indicated their diagnosis, treatment, and symptom origin interpretation. Both studies disconfirmed the first hypothesis and strongly supported the second. Only when stress was added did women receive significantly lower CHD diagnoses and cardiologist referrals than men and did the origin interpretation of women's CHD symptoms (e.g., chest pain) shift from organic to psychogenic. Neither participants' gender nor their attitude toward women influenced assessments.     

Cognitive influences on cross-language speech perception in infancy

Previous research has shown that young infants can discriminate both native and nonnative phonetic contrasts with ease. By 10 to 12 months of age, however, infants—like adults—typically have difficulty discriminating consonant contrasts that are not used to distinguish meaning in their native language. Although the timing of this change in speech perception has been firmly established, little is currently known about the processes or mechanisms involved in this selective and adaptive reorganization in nonnative phonetic discrimination. This study was designed to determine if there is a relation between age-related changes in speech perception performance and other developing cognitive abilities. A total of 40 8- to 10-month-old infants were tested on a nonnative consonant discrimination task and then on two additional tasks (a visual categorization task and an object search task) in an attempt to determine whether changes in nonnative consonant perception coincide with changes in these other areas of cognitive/perceptual functioning. The results indicate that changes in task performance occur in synchrony across all three tasks, and that this synchrony is not explained by simple age effects. These findings suggest that domain-general cognitive/perceptual competencies may influence developmental changes in speech perception by the end of the 1st year of life.     

Gun attitudes on campus: United and divided by safety needs

All people share a need for safety. Yet people’s pursuit of safety can conflict when it comes to guns, with some people perceiving guns as a means to safety and others perceiving guns as a threat to safety. We examined this conflict on a U.S. college campus that prohibits guns. We distinguished between people (N = 11,390) who (1) own a gun for protection, (2) own a gun exclusively for reasons other than protection (e.g., collecting, sports), and (3) do not own a gun. Protection owners felt less safe on campus and supported allowing guns on campus. They also reported that they and others would feel safer and that gun violence would decrease if they carried a gun on campus. Non-owners and non-protection owners felt the reverse. The findings suggest that protection concerns, rather than gun-ownership per se, account for diverging perceptions and attitudes about guns and gun control.     

Believing is seeing: how rumors can engender false memories in preschoolers

This study examined how an erroneous rumor circulated among preschoolers can influence their memory. One fourth of the children overheard a rumor from an adult conversation in which it was alleged that an event the children had not experienced themselves had occurred. A second fourth were the classmates of those who overheard the rumor. A third group had no exposure to the rumor. The remaining children actually experienced the event suggested by the rumor. One week later, the children were interviewed in either a neutral or a suggestive manner. Results from a second interview after a 2-week delay revealed that under both interview conditions, children who overheard the rumor, either from the adult conversation or during naturally occurring interactions with classmates, were as likely to report experiencing the rumored but nonexperienced event as were those who actually experienced it. Most reports of the rumored but nonexperienced event were in children's free recall and were accompanied by high levels of fictitious elaboration.