Genetic and environmental origins of verbal and performance components of cognitive delay in 2-year-olds.

The authors investigated the etiology of several measures of cognitive delay. Verbal (V) and performance (P) abilities were assessed in over 3,000 pairs of 2-year-old twins. Group-differences heritability for general delay (the lowest 5% of the V and P composite) was 35%. However, V and P delays considered independently showed large differences in group heritability (77% for V vs. 40% for P). Specific delays with comorbid cases eliminated showed an even greater difference in group heritability (78% vs. 22%, respectively). The small sample comorbid for both V and P delay also yielded high group heritability for both V (77%) and P (93%) scores. Shared environmental factors also differed in magnitude for V (20%) and P (41%) delays. Because the genetic and environmental origins of V and P delays in infancy differ, they are better considered separately rather than combined into a composite measure of general cognitive delay.     

Conditioned suppression of bar-pressing behavior by stimuli associated with drugs

Ten naive male albino rats were trained to press a bar under a variable-interval 30-sec schedule with water as the reinforcer in two experiments. This behavior was disrupted by chlorpromazine in Experiment I (two rats) and by lysergic acid diethylamide (LSD) in both Experiment I (two rats) and Experiment II (six rats). The administration of the drug was paired with an originally neutral white light. After several pairings with either drug, the light also depressed behavior. When the light was no longer paired with drug, the depression effect extinguished much faster than is usually observed in conditioned suppression studies.     

The comparability of verbal and nonverbal semantic differential scales in a joint semantic space

As an alternative to the verbal Semantic Differential (SD) measure of affective meaning systems, a nonverbal instrument-the Graphic Differential (GD)-has been developed for subject populations who have difficulty in verbal ratings. However, the factor structures of the pictographic scales have never been examined in a joint-verbal and nonverbal-semantic space as to whether their structures are equivalent to the affective systems defined by the verbal markers. The present study assessed this issue by reanalyzing the French (1977) data. The results indicated that when verbal SD and nonverbal GD scales were factor-analyzed separately, the three-dimensional structures of Evaluation (E), Potency (P), and Activity (A) were recaptured in both domains. However, when they were analyzed simultaneously in a joint semantic space, only the E and A dimensions were congruent. The GD P scales carried the meanings of denotative Heaviness, rather than the affective Potency. For future investigation, suggestion was made to systematically study both the affective and denotative semantic features within the contexts of nonverbal communciations.The authors made equal contributions toward the completion of the present research.     

Semantic activation in action planning

Four experiments investigated activation of semantic information in action preparation. Participants either prepared to grasp and use an object (e.g., to drink from a cup) or to lift a finger in association with the object's position following a go/no-go lexical-decision task. Word stimuli were consistent to the action goals of the object use (Experiment 1) or to the finger lifting (Experiment 2). Movement onset times yielded a double dissociation of consistency effects between action preparation and word processing. This effect was also present for semantic categorizations (Experiment 3), but disappeared when introducing a letter identification task (Experiment 4). In sum, our findings indicate that action semantics are activated selectively in accordance with the specific action intention of an actor.     

Brain dopamine and kinematics of graphomotor functions

Three experiments were performed in an attempt to achieve a better understanding of the effect of dopamine on handwriting. In the first experiment, kinematic aspects of handwriting movements were compared between healthy participants and patients with Parkinson's disease (PD) on their usual dopaminergic treatment and following withdrawal of dopaminergic medication. In the second experiment, the writing performance of healthy participants with a hyperechogenicity of the substantia nigra as detected by transcranial sonography (TCS) was compared with the performance of healthy participants with low echogenicity of the substantia nigra. The third experiment examined the effect of central dopamine reduction on kinematic aspects of handwriting movements in healthy adults using acute phenylalanine and tyrosine depletion (APTD). A digitising tablet was used for the assessment of handwriting movements. Participants were asked to perform a simple writing task. Movement time, distance, velocity, acceleration and measures of fluency of handwriting movements were measured. The kinematic analysis of handwriting movements revealed that alterations of central dopaminergic neurotransmission adversely affect movement execution during handwriting. In comparison to the automatic processing of handwriting movements displayed by control participants, participants with an altered dopaminergic neurotransmission shifted from an automatic to a controlled processing of movement execution. Central dopamine appears to be of particular importance with regard to the automatic execution of well-learned movements.     

The mere exposure effect is sensitive to color information: evidence for color effects in a perceptual implicit memory test

Priming effects in perceptual tests of implicit memory are assumed to be perceptually specific. Surprisingly, changing object colors from study to test did not diminish priming in most previous studies. However, these studies used implicit tests that are based on object identification, which mainly depends on the analysis of the object shape and therefore operates color-independently. The present study shows that color effects can be found in perceptual implicit tests when the test task requires the processing of color information. In Experiment 1, reliable color priming was found in a mere exposure design (preference test). In Experiment 2, the preference test was contrasted with a conceptually driven color-choice test. Altering the shape of object from study to test resulted in significant priming in the color-choice test but eliminated priming in the preference test. Preference judgments thus largely depend on perceptual processes. In Experiment 3, the preference and the color-choice test were studied under explicit test instructions. Differences in reaction times between the implicit and the explicit test suggest that the implicit test results were not an artifact of explicit retrieval attempts. In contrast with previous assumptions, it is therefore concluded that color is part of the representation that mediates perceptual priming.     

Factors underlying expectancies of success and achievement: the influential roles of need for cognition and general or specific self-concepts

It has been assumed that task-specific self-concepts are more important than general self-concepts in determining expectancies of success and subsequent achievement. The authors argue here that the influence varies depending on need for cognition (NFC). Findings from Study 1 (N=104) showed that expectancies of success in an academic task could be predicted from specific self-concept for individuals with a high NFC and from general self-concept for individuals with a low NFC. In Study 2 (N=193), where cognitive load was manipulated, given a high cognitive load, only general self-concept was predictive of success expectancies, independent of NFC. In Study 3 (N=197), given a high relevance of correct expectancy ratings, only specific self-concept was predictive of expectancies and actual achievement, independent of NFC. In Studies 4 and 5, the results from Study 1 concerning the prediction of expectancies (as well as achievement) reappeared in a physical and a social domain.     

Effects of implicit power motivation on men's and women's implicit learning and testosterone changes after social victory or defeat

Two studies examined interactions of implicit power motivation and experimentally varied victory or defeat in a contest on implicit learning of a visuomotor sequence associated with the contest outcome and changes in testosterone and self-reported affect. In men and women, power motivation predicted enhanced learning (sequence-execution accuracy) after a victory and impaired learning after a defeat. In men, power motivation predicted testosterone increases among winners and decreases among losers, and testosterone decreases mediated the negative effect of power motivation on learning in losers. In women, power motivation predicted postcontest testosterone increases, particularly among losers. In both men and women, self-reported affective states were influenced only by contest outcome and were unrelated to participants' testosterone changes or implicit learning.