Infant lightness perception: do 4-month-old infants follow Wallach's ratio rule?

When adults view a test disk embedded in a higher-luminance surround, the perceived lightness of the disk is largely determined by the surround-to-disk (S/D) luminance ratio (Wallach's ratio rule). Performance of 4-month-old infants tested with a forced-choice novelty-preference technique was consistent with predictions based on Wallach's ratio rule. This result suggests that the ability to extract and maintain information about local luminance ratios is present early in infancy. This ability is likely to contribute to the development of lightness constancy.     

Semantic categorization in the human brain: spatiotemporal dynamics revealed by magnetoencephalography

We examined the cortical representation of semantic categorization using magnetic source imaging in a task that revealed both dissociations among superordinate categories and associations among different base-level concepts within these categories. Around 200 ms after stimulus onset, the spatiotemporal correlation of brain activity elicited by base-level concepts was greater within than across superordinate categories in the right temporal lobe. Unsupervised clustering of data showed similar categorization between 210 and 450 ms mainly in the left hemisphere. This pattern suggests that well-defined semantic categories are represented in spatially distinct, macroscopically separable neural networks, independent of physical stimulus properties. In contrast, a broader, task-required categorization (natural/man-made) was not evident in our data. The perceptual dynamics of the categorization process is initially evident in the extrastriate areas of the right hemisphere; this activation is followed by higher-level activity along the ventral processing stream, implicating primarily the left temporal lobe.     

The early origins of goal attribution in infancy

We contrast two positions concerning the initial domain of actions that infants interpret as goal-directed. The 'narrow scope' view holds that goal-attribution in 6- and 9-month-olds is restricted to highly familiar actions (such as grasping). The cue-based approach of the infant's 'teleological stance', however, predicts that if the cues of equifinal variation of action and a salient action effect are present, young infants can attribute goals to a 'wide scope' of entities including unfamiliar human actions and actions of novel objects lacking human features. It is argued that previous failures to show goal-attribution to unfamiliar actions were due to the absence of these cues. We report a modified replication of Woodward (1999) showing that when a salient action-effect is presented, even young infants can attribute a goal to an unfamiliar manual action. This study together with other recent experiments reviewed support the 'wide scope' approach indicating that if the cues of goal-directedness are present even 6-month-olds attribute goals to unfamiliar actions.     

Contemporary longitudinal methods for the study of trauma and posttraumatic stress disorder

Traditional methods for analyzing trends in longitudinal data have typically emphasized average group change over time. In this article, we propose multilevel, regression-based methods for examining inter-individual differences in intra-individual change and apply these methods to research in trauma and posttraumatic stress disorder (PTSD). The outcome or dependent variable of interest is reconceptualized as an index of dynamic change reflecting the trend or trajectory of an individual's PTSD symptom severity scores across time. A basic statistical model is presented, and analyses and findings are demonstrated with an existing database used in previously published studies. The methods offer promise for future study of the natural course of PTSD chronicity or recovery, risk and resilience factors that influence individual growth or decline, and critical timepoints for intervention.     

Genetics of posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is a prevalent anxiety disorder marked by behavioral, physiologic, and hormonal alterations. PTSD is disabling and commonly follows a chronic course. The etiology of PTSD is unknown, although exposure to a traumatic event constitutes a necessary, but not sufficient, factor. A twin study of Vietnam veterans has shown significant genetic contribution to PTSD. The fact that PTSD's underlying genotypic vulnerability is only expressed following trauma exposure limits the usefulness of family-based linkage approaches. In contrast to the other major psychiatric disorders, large studies for the search of underlying genes have not been described in PTSD to date. Complementary approaches for locating involved genes include association-based studies employing case-control or parental genotypes for transmission dysequilibrium analysis and quantitative trait loci studies in animal models. Identification of susceptibility genes will increase our understanding of traumatic stress disorders and help to elucidate their molecular basis. The current review provides an up-to-date outline of progress in the field of PTSD.     

Regulation of glutamate synapses by nicotinic acetylcholine receptors in auditory cortex

Acetylcholine plays an important role in regulating the processing of sensory stimuli, and understanding its specific cellular actions is critical to understanding how sensory cortex develops and functions in different behavioral states. Here we review recent work on the cellular effects of nicotinic receptor activation in auditory cortex and describe how these actions could affect systems-level auditory function. In particular, we describe a novel function of nicotinic acetylcholine receptors to regulate glutamate synapses containing N-methyl-D-aspartate receptors during early postnatal development. The transient regulation of developing glutamate synapses also defines a window of vulnerability during which exposure to exogenous nicotine disrupts synapse development. Thus, it appears that nicotinic regulation of glutamate synapses is a critical feature of auditory cortex development.     

Understanding mass allegations of satanist child abuse in early modern Sweden: demographic data relevant to the Rättvik outbreak of 1670-1671

Demographic characteristics of 79 women who were accused of satanist child abductions in the parish of R?ttvik, Sweden, in 1670-1671; 53 adults who promoted such accusations by bringing children to interrogations; and samples from the general population of R?ttvik were compared. Results indicate that men were more likely to promote allegations of satanism than women and that these men were more likely to be married than the average R?ttvik male. Promoters of allegations were older than average parishioners, and land-owning people who were involved in the panic owned more land than landowners who were not involved. People who were involved in the panic knew less about Luther's catechism than members of the general population. It is suggested that most of these findings may reflect a tendency of people who lived in the proximity of children to become involved in the panic.     

Teleological reasoning in infancy: the nai;ve theory of rational action

Converging evidence demonstrates that one-year-olds interpret and draw inferences about other's goal-directed actions. We contrast alternative theories about how this early competence relates to our ability to attribute mental states to others. We propose that one-year-olds apply a non-mentalistic interpretational system, the 'teleological stance' to represent actions by relating relevant aspects of reality (action, goal-state and situational constraints) through the principle of rational action, which assumes that actions function to realize goal-states by the most efficient means available. We argue that this early inferential principle is identical to the rationality principle of the mentalistic stance - a representational system that develops later to guide inferences about mental states.     

Memory bias for faces that are perceived as hostile by crime victims with acute post-traumatic stress disorder

The present study tested, and found support for, the hypotheses that crime victims with acute post-traumatic stress disorder have: (i) a general memory impairment for faces; and (ii) a memory bias for faces that they perceive as hostile, even when these faces are not arranged to show any hostile face expressions. It is suggested that crime victims with acute post-traumatic stress disorder perform worse on recognition memory due to impaired concentration, and that they allocate their limited attentional resources to the detection of hostility in others in order to avoid being victimized again. This produces a memory bias for perceived hostility even in relatively innocuous everyday interactions with others, which contributes to maintaining the sense of serious current threat that characterizes post-traumatic stress disorder.