Incentive downshifts evoke search repertoires in rats.

Negative incentive contrast effects (NCEs) have typically been attributed to frustration or the decremental generalization of learned associations. The purpose of these experiments was to clarify the relation of NCEs to the repertoires of functional search behaviors evoked by incentive downshifts. Rats shifted from 32% to 4% sucrose-solution decreased consummatory responses but increased nose-down locomotion, orientation, location entries, and sampling of alternatives relative to unshifted controls. These changes in behavior were terminated or failed to occur under incentive upshifts. Furthermore, reward downshifts did not produce avoidance of the location of the shifted incentive. Increased search occurred whether or not alternative reward locations were available. Together the evidence suggests that NCEs are related to evoked search modes supporting a repertoire of functional behaviors related to finding food.     

Attentional blink for color

Colored letters were presented by means of rapid serial visual presentation (RSVP). Two letters (T1 and T2) were targets that required a speeded (T1) or delayed (T2) response. T1 was shown on half of the trials. Two tasks were performed in the experimental conditions. Task 1 required a discrimination between 2 letters (when T1 was shown) or an indication that T1 was absent. In Experiment 1, Task 2 was to detect the presence of a unique color in the RSVP stream (e.g., green in a stream of alternating red and gray). In Experiment 2, Task 2 was to report the color of the first colored letter to appear in the RSVP stream. The lag between T1 and T2 in the RSVP stream was manipulated. Accuracy of color reports in Task 2 was poor at shorter lags and improved as the lag was lengthened in both experiments, demonstrating an attentional blink for chromatic information. Theoretical implications of the results are discussed.     

Heroin addicts have higher discount rates for delayed rewards than non-drug-using controls

Fifty-six heroin addicts and 60 age-matched controls were offered choices between monetary rewards ($11-$80) available immediately and larger rewards ($25-$85) available after delays ranging from 1 week to 6 months. Participants had a 1-in-6 chance of winning a reward that they chose on one randomly selected trial. Delay-discounting rates were estimated from the pattern of participants' choices. The discounting model of impulsiveness (Ainslie, 1975) implies that delay-discounting rates are positively correlated with impulsiveness. On average, heroin addicts' discount rates were twice those of controls (p = .004), and discount rates were positively correlated with impulsivity as measured by self-report questionnaires (p < .05). The results lend external validity to the delay-discounting rate as a measure of impulsiveness, a characteristic associated with substance abuse.     

What is the nature of increased Stroop interference in schizophrenia?

In comparison to controls, patients with schizophrenia classically display (1) an overall slowing in response times (RTs) and (2) a disproportionate slowing in RTs in the conflict condition of the Stroop color/word interference task. These two effects appear repeatedly in the card version of the Stroop task but were not replicated in a number of studies using a computer item-by-item version of the task. The present study was aimed at understanding the exact nature of the increased interference classically found in the performance of patients with schizophrenia in the card version of the Stroop task. We used a computer trial-by-trial version in which we investigated the effects of two major methodological differences between the two versions: (1) blocked (card version) versus mixed (computer version) presentation of the neutral, congruent and conflict conditions and (2) presence (card version) versus absence (computer version) of distractors in the spatial surrounding of the target. We found an overall slowing in performance and a disproportionate slowing in the conflict condition for patients with schizophrenia but only when the target was surrounded by distractors (in Experiments 2 and 3). The data are discussed in terms of a deficit in selective attention and inhibitory processes in schizophrenia.     

Early developments in the ability to understand the relation between stimulus and reward

Delayed nonmatching to sample (DNMS) is used to test the recognition memory function dependent on the medial temporal lobe. Children cannot succeed on this task until about 21 months. Because robust recognition is present well before then, the late emergence of another ability must account for the late success on DNMS. Evidence is presented here that the critical late-maturing competence is the ability to grasp the relation between stimulus and reward--that is, to understand that the stimulus is a symbol or marker for the reward. Infants of 9 and 12 months were tested on 3 conditions of DNMS. A sample object was presented. After a delay, the sample and a novel object appeared; choice of the novel object was rewarded. In the standard task, the reward was in a well beneath the stimulus. In the verbal-reward condition the reward was not a separate object but was praise and applause. In the Velcro condition, the reward, although a separate and separable object, was attached to the base of the stimulus. Most infants at both ages succeeded in the verbal-reward and Velcro conditions but not in the standard condition.     

The relations between temperament and empathy in 2-year-olds.

The role of infant and toddler temperament in the prediction of empathy in 2-year-old children was examined. Assessments of temperament included reactivity and affect observed at 4 months of age, as well as inhibition at Age 2. Empathy was measured in 2-year-old children's responses to simulations of distress performed by their mothers and by an unfamiliar person. Children showed relatively more concern for the mother's distress, but they were also responsive to unfamiliar victims. Infants who were unreactive and showed little affect also showed less empathy toward the unfamiliar adult almost 2 years later. Inhibition toward an unfamiliar adult (but not toward the mother) at 2 years of age was negatively related to empathy. Inhibited temperament may thus have a major impact on young children's empathy in unfamiliar contexts. Findings also highlight the need to consider early underarousal as another dimension of temperament that may dampen expressions of empathic concern.     

MMPI-A in the inpatient assessment of adolescents with eating disorders.

The MMPI-A (Butcher et al., 1992), like the older MMPI (Hathaway & McKinley, 1983), distinguishes between anorexia and bulimia. In this study, 245 adolescent girls diagnosed with anorexia, bulimia, or eating disorder not otherwise specified completed the MMPI-A. Multivariate analyses revealed significant differences between anorexia and bulimia on the MMPI-A's validity, clinical, content, and supplementary scales, particularly suggesting multiple impulse control problems among bulimic patients. However, profiles were also more homogeneous across eating disorder groups than in studies using the older MMPI, with high points involving some combination of Scales 1, 2, 3, and 0 for two thirds of the patients in this study. Implications are considered for understanding the common and differential psychopathology of eating disorders.     

Executive functioning and compliance in HIV patients

25 adult HIV patients were evaluated in a study of appointments, medication, and compliance with restrictions on sexual activity. The Executive Interview (EXIT) was useful in assessing these patients for cognitive difficulties; compliance with medication and countertransference issues were negatively correlated with EXIT scores.