Examining neurochemical determinants of inspection time: Development of a biological model

Inspection time (IT), an information-processing correlate of psychometric intelligence, has been extensively studied. Previous research has shown that IT is a reliable correlate of psychometric intelligence across different developmental periods, mirroring developmental trends of fluid intelligence. Despite this extensive previous literature, very little is known about the biological basis of IT. In the present review, we discuss recent results from our laboratories examining the neurochemical determinants of IT. In this review, we outline the significance of several studies in which performance on the IT task is measured before and after modulating key human central nervous system (CNS) neurotransmitters and receptor systems (e.g., cholinergic, serotonergic, noradrenergic, and dopaminergic systems). The results of these studies indicate a primarily cholinergic basis for IT, although other aspects of psychometric intelligence may have serotonergic and dopaminergic determinants in addition to a cholinergic basis. The results are consistent with data reporting cholinergic depletion and impaired IT performance in dementia of the Alzheimer's type (DAT). Speculatively, we propose that compounds that enhance the release of the neurotransmitter acetylcholine (Ach) will improve IT and the variance that IT shares with IQ test performance.     

Effects of early institutionalization on the development of emotion processing: a case for relative sparing?

We tested the capacity to perceive visual expressions of emotion, and to use those expressions as guides to social decisions, in three groups of 8‐ to 10‐year‐old Romanian children: children abandoned to institutions then randomly assigned to remain in ‘care as usual’ (institutional care); children abandoned to institutions then randomly assigned to a foster care intervention; and community children who had never been institutionalized. Experiment 1 examined children's recognition of happy, sad, fearful, and angry facial expressions that varied in intensity. Children assigned to institutional care had higher thresholds for identifying happy expressions than foster care or community children, but did not differ in their thresholds for identifying the other facial expressions. Moreover, the error rates of the three groups of children were the same for all of the facial expressions. Experiment 2 examined children's ability to use facial expressions of emotion to guide social decisions about whom to befriend and whom to help. Children assigned to institutional care were less accurate than foster care or community children at deciding whom to befriend; however, the groups did not differ in their ability to decide whom to help. Overall, although there were group differences in some abilities, all three groups of children performed well across tasks. The results are discussed in the context of theoretical accounts of the development of emotion processing.     

Student learning as the basis for reinforcement to the instructor

The present study reinforced the two instructors of two students with profound mental retardation first for the instructors' training behaviors, then for improved student learning in a multiple baseline across responses design. Reinforcement of the instructors' training behaviors increased their training behaviors, replicating the findings of previous studies, but had no effect on student learning. When the reinforcement for the instructors was instead made contingent upon student learning, the student learning improved and the instructors' high level of training behaviors was maintained. In addition, the instructors began to request training for themselves. These findings suggest that staff motivation programs for instructors might usefully base the reinforcers not only on the instructor's performance, but on the progress of their students.     

SEPARATE AND COMBINED EFFECTS OF METHYLPHENIDATE AND A BEHAVIORAL INTERVENTION ON DISRUPTIVE BEHAVIOR IN CHILDREN WITH MENTAL RETARDATION

We investigated the separate and combined effects of a behavioral intervention and methylphenidate (Ritalin®) on disruptive behavior and task engagement in 3 children with severe to profound mental retardation. The behavioral intervention involved differential reinforcement of appropriate behavior and guided compliance. All 3 children demonstrated decreased disruptive behavior and improved task engagement in response to the behavioral intervention. Two of the 3 children demonstrated similar improvement in response to methylphenidate. Although both interventions were highly effective for these 2 participants, the relative efficacy of the interventions varied between the 2 children. There was no evidence of an additive or synergistic effect of the two interventions, but the high efficacy of each intervention alone limited our ability to detect such effects.