Development of the infant's hand preference for visually directed reaching: Preliminary report of a longitudinal study

The development of hand preference in infancy was investigated longitudinally by using a visually-directed reaching task. Thirty-two infants, equally divided into groups of familial right- and left-handed boys and girls, were tested every 3 weeks from 24 to 39 weeks of age and once again at 52 weeks. Group trends for the development of hand preference were differentiated by familial handedness and sex of the infant. At all ages, test object position (to the infant's right or left) strongly influenced the hand used for reaching. Marked variability both between and within infants demonstrated an instability of early hand preference, an effect that could be appreciated fully only with a prospective longitudinal design. The results thus suggest that the development of hand preference for reaching is highly variable, discontinuous, and related to the interaction of sex and familial handedness.     

What is learned in sequential learning? An associative model of reward magnitude serial-pattern learning

A computational model of sequence learning is described that is based on pairwise associations and generalization. Simulations by the model predicted that rats should learn a long monotonic pattern of food quantities better than a nonmonotonic pattern, as predicted by rule-learning theory, and that they should learn a short nonmonotonic pattern with highly discriminable elements better than 1 with less discriminable elements, as predicted by interitem association theory. In 2 other studies, the model also simulated behavioral "rule generalization," "extrapolation," and associative transfer data motivated by both rule-learning and associative perspectives. Although these simulations do not rule out the possibility that rats can use rule induction to learn serial patterns, they show that a simple associative model can account for the classical behavioral studies implicating rule learning in reward magnitude serial-pattern learning.     

Processing of temporal duration information in working memory after frontodorsal tumour excisions

This study aimed to test the hypothesis that impairments of temporal duration processing after frontal lobe lesions reflect deficits in executive monitoring functions rather than a domain-specific deficit in the maintenance of duration information in working memory. Patients with frontodorsal lesions, clinical controls with post-central lesions, and healthy controls performed recognition and classification tasks, which should allow for testing maintenance and monitoring functions, respectively. Results showed mild non-selective impairments of the frontal patients on both temporal and spatial recognition tasks, but a marked selective degradation on temporal classification while performance on spatial classification was unimpaired. This suggests that maintenance of duration information in working memory after frontal lesions is basically preserved but that, depending on executive task characteristics, there is a specific deficit in the strategic organization of this type of information.     

Priming visual face-processing mechanisms: electrophysiological evidence

Accumulated evidence from electrophysiology and neuroimaging suggests that face perception involves extrastriate visual mechanisms specialized in processing physiognomic features and building a perceptual representation that is categorically distinct and can be identified by face-recognition units. In the present experiment, we recorded event-related brain potentials in order to explore possible contextual influences on the activity of this perceptual mechanism. Subjects were first exposed to pairs of small shapes, which did not elicit any face-specific brain activity. The same stimuli, however, elicited face-specific brain activity after subjects saw them embedded in schematic faces, which probably primed the subjects to interpret the shapes as schematic eyes. No face-specific activity was observed when objects rather than faces were used to form the context. We conclude that the activity of face-specific extrastriate perceptual mechanisms can be modulated by contextual constraints that determine the significance of the visual input.     

Still the Heart of Darkness: The Ebola Virus and the Meta-Narrative of Disease in The Hot Zone

Still the Heart of Darkness analyzes Richard Preston's best-selling account of an Ebola virus outbreak in Reston, Virginia in 1989. Through a textual examination of The Hot Zone, this essay demonstrates how Preston grounds his narrative about the threat of rare emerging viruses from the third world in terms of the colonialist discourse about Africa as the white man's grave, most notably Joseph Conrad's Heart of Darkness. By foregrounding previous outbreaks in Africa, Preston simultaneously darkens its landscape and inscribes the Ebola filovirus as an external biological threat to Americans in a post-Cold War world with porous borders.     

Salient stimuli in advertising: the effect of contrast interval length and type on recall

Salient auditory stimuli (e.g., music or sound effects) are commonly used in advertising to elicit attention. However, issues related to the effectiveness of such stimuli are not well understood. This research examines the ability of a salient auditory stimulus, in the form of a contrast interval (CI), to enhance recall of message-related information. Researchers have argued that the effectiveness of the CI is a function of the temporal duration between the onset and offset of the change in the background stimulus and the nature of this stimulus. Three experiments investigate these propositions and indicate that recall is enhanced, providing the CI is 3 s or less. Information highlighted with silence is recalled better than information highlighted with music.     

Task demands and representation in long-term repetition priming

The effects of task demands on the representation of letter strings in long-term repetition priming (LTRP) were explored in two lexical decision experiments. The stimuli in both experiments were words and nonwords, some presented horizontally and some vertically. The only difference between the two experiments was the response required by the participant. In Experiment 1, the participants pressed one of two buttons, indicating whether or not a given stimulus was a word. In Experiment 2, the participants pressed one of four buttons, indicating both the lexical status and the orientation of a given stimulus. The results were that in Experiment 1, LTRP was not disrupted by a change in stimulus orientation, whereas in Experiment 2 it was, suggesting that the nature of the stimulus representation utilized in LTRP is partially dependent on the demands of the task.     

The ties that bind what is known to the recall of what is new

Cued recall success varies with what people know and with what they do during an episode. This paper focuses on prior knowledge and disentangles the relative effects of 10 features of words and their relationships on cued recall. Results are reported for correlational and multiple regression analyses of data obtained from free association norms and from 29 experiments. The 10 features were only weakly correlated with each other in the norms and, with notable exceptions, in the experiments. The regression analysis indicated that forward cue-to-target strength explained the most variance, followed by backward target-to-cue strength. Target connectivity and set size explained the next most variance, along with mediated cue-to-target strength. Finally, frequency, concreteness, shared associate strength, and cue set size also contributed significantly to recall. Taken together, indices of prior word knowledge explain 49% of the recall variance. Theoretically driven equations that use free association to predict cued recall were also evaluated. Each equation was designed to condense multiple indices of word interconnectivity into a single predictor.     

Mean response times, variability, and skew in the responding of ADHD children: a response time distributional approach

Response time (RT) distributions from three fixed foreperiod conditions (2, 4, and 8 s) in a warned four-choice RT task were obtained for a group of boys with attention-deficit/hyperactivity disorder, combined type (ADHD; n = 17) and for two groups of normal control boys (age-matched, n = 18, and younger-aged, n = 10). Quantitative measures of distributional shape were derived by fitting the ex-Gaussian distributional model to the individual RT data. Statistical results indicate that the ADHD distributions differ from the age-matched control distributions with respect to the size of the tail (larger for the ADHD boys), but differ from the younger control distributions with respect to the location of the leading edge (slower for the younger control boys). Receiver operating characteristic (ROC) results reveal that the ex-Gaussian exponential component is highly diagnostic of the ADHD boys.