The control of responsiveness in ADHD by catecholamines: evidence for dopaminergic, noradrenergic and interactive roles

We explore the neurobiological bases of attention deficit hyperactivity disorder (ADHD) from the viewpoint of the neurochemistry and psychopharmacology of the catecholamine-based behavioural systems. The contributions of dopamine (DA) and noradrenaline (NA) neurotransmission to the motor and cognitive symptoms of ADHD (e.g. hyperactivity, variable and impulsive responses) are studied in rodent and primate models. These models represent elements of the behavioural units observed in subjects with ADHD clinically, or in laboratory settings (e.g. locomotion, changed sensitivity/responsivity to novelty/reinforcement and measures of executive processing). In particular, the models selected emphasize traits that are strongly influenced by mesocorticolimbic DA in the spontaneously hypertensive (SHR) and the Naples high excitability (NHE) rat lines. In this context, the mode of action of methylphenidate treatment is discussed. We also describe current views on the altered control by mesolimbic catecholamines of appropriate and inappropriate goal-directed behaviour, and the tolerance or intolerance of delayed reinforcement in ADHD children and animal models. Recent insights into the previously underestimated role of the NA system in the control of mesocortical DA function, and the frontal role in processing information are elaborated.     

Organizational justice and Black applicants' reactions to affirmative action

Using organizational justice as a guiding framework, the authors studied perceptions of affirmative action programs by presumed beneficiaries. Three conceptual issues were addressed: (a) the content of different affirmative action plans; (b) the 3-way interaction among distributive, procedural, and interactional justice; and (c) the distinction between outcome favorability and distributive justice. These ideas were tested with a sample of Black engineering students who responded to 1 of 6 plans. Participants distinguished among the various plans, with some policies being viewed as more fair than others. In addition, a 3-way interaction among the 3 types of organizational justice was observed. Specifically, the 2-way interaction between distributive and interactional fairness was only significant when procedural justice was low. Implications for organizational justice and for the design of affirmative action programs are discussed.     

A systematic evaluation of food textures to decrease packing and increase oral intake in children with pediatric feeding disorders

This study examined packing (pocketing or holding accepted food in the mouth) in 3 children who were failing to thrive or had inadequate weight gain due to insufficient caloric intake. The results of an analysis of texture indicated that total grams consumed were higher when lower textured foods were presented than when higher textured foods were presented. The gram intake was related directly to levels of packing. That is, high levels of packing were associated with higher textured foods and low gram intake, and low levels of packing were associated with lower textured foods and high gram intake. All participants gained weight when texture of foods was decreased. Packing remained low during follow-up for 2 participants even when the texture of food was increased gradually over time. These data are discussed in relation to avoidance, response effort, and skill deficit.     

The distribution and development of handedness for manual gestures in captive chimpanzees (Pan troglodytes)

This article describes the distribution and development of handedness for manual gestures in captive chimpanzees. Data on handedness for unimanual gestures were collected in a sample of 227 captive chimpanzees. Handedness for these gestures was compared with handedness for three other measures of hand use: tool use, reaching, and coordinated bimanual actions. Chimpanzees were significantly more right-handed for gestures than for all other measures of hand use. Hand use for simple reaching at 3 to 4 years of age predicted hand use for gestures 10 years later. Use of the right hand for gestures was significantly higher when gestures were accompanied by a vocalization than when they were not. The collective results suggest that left-hemisphere specialization for language may have evolved initially from asymmetries in manual gestures in the common ancestor of chimpanzees and humans, rather than from hand use associated with other, non-communicative motor actions, including tool use and coordinated bimanual actions, as has been previously suggested in the literature.     

Executive control within strategic deception: a window on early cognitive development?

Recently it has been claimed that the difficulty young children have with tests of strategic deception may be due to limitations in executive control rather than lack of insight into mental concepts. In the studies reported here we asked how reducing the executive demands of one measure of strategic deception, the windows task (J. Russell, N. Mauthner, S. Sharpe, & T. Tidswell, 1991), would affect performance. Study 1 demonstrated that both providing an artificial response medium and having children play in partnership enabled 3-year-olds to adopt a successful strategy. Study 2 examined whether social or executive factors accounted for the good performance of children when they played in partnership. Study 3 ruled out the possibility that the effectiveness of the artificial media was a result of reducing social intimidation-the manipulations were effective even in the presence the opponent. These results argue for executive factors playing a substantial role in the development of strategic deception.     

The role of perceptual load in processing distractor faces

It has been established that successful ignoring of irrelevant distractors depends on the extent to which the current task loads attention. However, the previous load studies have typically employed neutral distractor stimuli (e.g., letters). In the experiments reported here, we examined whether the perception of irrelevant distractor faces would show the same effects. We manipulated attentional load in a relevant task of name search by varying the search set size and found that whereas congruency effects from meaningful nonface distractors were eliminated by higher search load, interference from distractor faces was entirely unaffected by search load. These results support the idea that face processing may be mandatory and generalize the load theory to the processing of meaningful and more complex nonface distractors.     

Familiarity, ambivalence, and firm reputation: is corporate fame a double-edged sword?

This research questioned the proposition that corporate familiarity is positively associated with firm reputation. Student images of familiar and unfamiliar Fortune 500 corporations were examined in 4 experiments. The results suggested that, consistent with behavioral decision theory and attitude theory, highly familiar corporations provide information that is more compatible with the tasks of both admiring and condemning than less familiar corporations. Furthermore, the judgment context may determine whether positive or negative judgments are reported about familiar companies. The notion that people can simultaneously hold contradictory images of well-known firms may help to explain the inconsistent findings on the relation between familiarity and reputation.     

Conversion theory and simultaneous majority/minority influence: Can reactance offer an alternative explanation?

This study tested whether reactance theory can account for private acceptance of a minority opinion under simultaneous majority/minority influence (reactance against majority rather than conversion toward minority). Subjects were either exposed to simultaneous majority /minority influence or to a majority source only. As predicted by conversion theory, subjects moved away from the majority only in private and in the presence of a consistent minority. In the absence of a consistent minority, subjects accepted the majority opinion in private, ruling out reactance as an alternative explanation.     

Agreement between teachers' ratings and observations of hyperactivity,inattentiveness, and defiance

The relationship of directly observed classroom behavior and teacher ratings on questionnaires with a judgemental (Conners Teacher Rating Scale) or operational format was examined for 33 boys aged 6 years 5 months to 7 years 7 months. Results showed a high degree of association between observed and rated behavior. This association did not vary with the format of the rating scales but did vary with the nature of the behavior being rated. Defiance was more reliably rated than hyperactivity or inattentiveness. Several behaviors exerted a halo effect on ratings of hyperactivity, inattentiveness, and behavior problems. In particular, defiance toward a teacher increased the likelihood that a child would be rated as hyperactive or inattentive regardless of his observed level of activity or attentiveness. These results support the validity of behavior rating scales as screening measures for hyperactivity, inattentiveness, and defiance and indicate that a child's defiance and disobedience are significant causes of misclassification.