Second-order reversed phi.

In a first-order reversed-phi motion stimulus (Anstis, 1970), the black-white contrast of successive frames is reversed, and the direction of apparent motion may, under some conditions, appear to be reversed. It is demonstrated here that, for many classes of stimuli, this reversal is a mathematical property of the stimuli themselves, and the real problem is in perceiving forward motion, which involves the second- or third-order motion systems or both. Three classes of novel second-order reversed-phi stimuli (contrast, spatial frequency, and flicker modulation) that are invisible to first-order motion analysis were constructed. In these stimuli, the salient stimulus features move in the forward (feature displacement) direction, but the second-order motion energy model predicts motion in the reversed direction. In peripheral vision, for all stimulus types and all temporal frequencies, all the observers saw only the reversed-phi direction of motion. In central vision, the observers also perceived reversed motion at temporal frequencies above about 4 Hz, but they perceived movement in the forward direction at lower temporal frequencies. Since all of these stimuli are invisible to first-order motion, these results indicate that the second-order reversed-phi stimuli activate two subsequent competing motion mechanisms, both of which involve an initial stage of texture grabbing (spatiotemporal filtering, followed by fullwave rectification). The second-order motion system then applies a Reichardt detector (or equivalently, motion energy analysis) directly to this signal and arrives at the reversed-phi direction. The third-order system marks the location of features that differ from the background (the figure) in a salience map and computes motion in the forward direction from the changes in the spatiotemporal location of these marks. The second-order system's report of reversed movement dominates in peripheral vision and in central vision at higher temporal frequencies, because it has better spatial and temporal resolution than the third-order system, which has a cutoff frequency of 3-4 Hz (Lu & Sperling, 1995b). In central vision, below 3-4 Hz, the third-order system's report of resolvable forward movement of something salient (the figure) dominates the second-order system's report of texture contrast movement.     

Shape constancy from novel views

Prior experiments on shape constancy from novel views are inconclusive: Some show that shapes of objects can be recognized reliably from novel views, whereas others show just the opposite. Our analysis of prior results suggests that shape constancy from novel views is reliable when the object has properties that constrain its shape: The object has volumetric primitives, it has surfaces, it is symmetrical, it is composed of geons, its contours are planar, and its images provide useful topological information about its three-dimensional structure. To test the role of some of these constraints, we performed a set of experiments. Solid shapes (polyhedra) were shown on a computer monitor by means of kinetic depth effect. Experiment 1 showed that shape constancy can be reliably achieved when a polyhedron is represented by its contours (most of the constraints are present), but not when it is represented by vertices or by a polygonal line connecting the vertices in a random order (all the constraints are absent). Experiments 2 and 3 tested the role of individual constraints. Results of these experiments show that shape constancy from novel views is reliable when the object has planar contours and when the shapes of the contours together with topological information about the relations among the contours constrain the possible interpretations of the shape. Symmetry of the object and the topological stability of its image also contribute to shape constancy.     

Role of the serotonin transporter gene in temperament and character

The biosocial model postulates that personality is comprised of two broad domains: temperament, which is largely due to inherited variations in specific monoamine neurotransmitter systems; and character, which arises from socioculturally learned differences in values, goals, and self-concepts and is the strongest predictor of personality disorders. The model also proposes that serotonin modulates the temperament trait of harm avoidance. We analyzed the association of temperament and character traits with the 5-HTTLPR, an inherited variation that modulates serotonin transporter gene expression, in 634 volunteer subjects. Contrary to theory, the 5-HTTLPR was most strongly associated with the character traits of cooperativeness and self-directedness. Associations with the temperament traits of reward dependence and harm avoidance were weaker and could be attributable largely to cross-correlations with the character traits and demographic variables. Psychometric analysis indicated that the serotonin transporter influences two broad areas of personality, negative affect and social disaffiliation, that are consistent across inventories but are more concisely described by the 5-factor model of personality than by the biosocial model. These results suggest that there is no fundamental mechanistic distinction between character and temperament in regard to the serotonin transporter gene, and that a single neurotransmitter can influence multiple personality traits.     

Horsefeathers: a commentary on "evolutionary versus prototype analyses of the concept of disorder".

J. C. Wakefield's (1999) article further develops his harmful dysfunction (HD) model for disorder concepts. This commentary focuses on three areas. The first notes the imbalance in the debate between the Lilienfeld and Marino (1995) Roschian model and the HD model for disorder concepts. The second claims that Wakefield's purposes for the HD model have changed over the years and progressed toward irrelevance to psychopathology in general and toward irrelevance to actual nosologic, reimbursement, and sociopolitical controversies about disorder status. Further discussion is on how certain structural elements in Wakefield's arguments and current limitations of evolutionary theory permit a superficially attractive model for psychopathology. These arguments and limitations, however, harbor serious problems when confronted with actual disputes about disorders. The conclusion notes some virtues to Wakefield's inquiry, in style and substance.     

Perceptual organization of apparent motion in the Ternus display

A typical Ternus display has three sequentially presented frames, in which frame 1 consists of three motion tokens, frame 2 (blank) defines the interstimulus interval, and frame 3 has similar motion tokens with their relative positions shifted to the right. Interestingly, what appears to be a seemingly simple arrangement of stimuli can induce one of two distinct apparent-motion percepts in the observer. The first is an element-motion perception where the left-end token is seen to jump over its two neighboring tokens (inner tokens) to the right end of the display. The second is a group-motion perception where the entire display of the three tokens is seen to move to the right. How does the visual system choose between these two apparent-motion perceptions? It is hypothesized that the choice of motion perception is determined in part by the perceptual organization of the motion tokens. Specifically, a group-motion perception is experienced when a strong grouping tendency exists among the motion tokens belonging to the same frame. Conversely, an element-motion perception is experienced when a strong grouping tendency exists between the inner motion tokens in frames 1 and 3 (i.e. the two tokens that overlap in space between frames). We tested this hypothesis by varying the perceptual organization of the motion tokens. Both spatial (form similarity, 3-D proximity, common surface/common region, and occlusion) and temporal (motion priming) factors of perceptual organization were tested. We found that the apparent-motion perception of the Ternus display can be predictably affected, in a manner consistent with the perceptual organization hypothesis.     

Morphological errors in casual conversation.

Occasionally, listeners' strategies for dealing with casual speech lead them into an erroneous perception of the intended message-a slip of the ear. When such errors occur, listeners report hearing, as clearly and distinctly as any correctly perceived stretch of speech, something that does not correspond to the speakers' utterance. From a collection of almost 1000 examples of misperceptions in English conversation, perceptual errors involving morphology suggest that listeners expect monomorphemic forms and treat phonological information as primary. Listeners are not particularly attentive to morphological information and may supply inflectional morphemes as needed by context.     

Rule selection versus rule execution in preschoolers: an error-detection approach.

In 2 experiments, an error-detection approach was used to determine whether 3-year-olds' perseverative errors on the postswitch phase of the Dimensional Change Card Sort (DCCS) are due to lack of response control or representational inflexibility. In Experiment 1, 3-, 4-, and 5-year-olds watched a puppet sort perseveratively on the postswitch phase and evaluated its responses. Most 4- and 5-year-olds detected the puppet's perseverative errors, whereas most 3-year-olds failed to do so despite detecting errors on a simpler card sort. Experiment 2 revealed that 3-year-olds who failed to correctly evaluate the puppet's behavior tended to fail their own DCCS. Results imply that perseveration on the DCCS cannot be attributed to difficulty inhibiting prepotent motor responses. Instead, changes in rule use between 3 and 5 years of age are interpreted in terms of the development of representational flexibility.     

Psychiatric emergency rates during the Christmas season in the years 1991 to 1997

We compared the number of psychiatric admissions from the emergency room during the Christmas season, defined as the rate for the month of December, with those in other months. The psychiatric emergency rates were recorded for each month over six consecutive years, 1991 to 1997. The average number of emergency patients in none of the 12 months differed significantly from any of the remaining months (ANOVA, p > .05). Our data and those of other authors do not support the clinical lore that Christmas season is associated with higher rate of psychiatric emergencies.     

Perceived competence, social anxiety about physique, and enjoyment in testing situations among groups of mixed sex and girls only.

The purpose of the present study was to assess whether there are differences in agility and coordination performance, anxiety about physique, perceived competence, and enjoyment between girls (n = 56) performing within mixed-sex versus all-female high school classes in physical education. A series of between-group comparisons yielded no significant differences between groups on measures of performance, perceived competence, and anxiety about physique; however, the mixed-sex group reported significantly greater enjoyment on both psychomotor tests than the all-female group (ps < or = .05). Results are discussed within other contexts such as sport motivation and Weiss and Chaumeton's (1992) theory of youth sport development.     

Treatment issues during pregnancy and lactation

The lifetime incidence of mood disorders is twice as great in women compared with men, with the highest risk occurring during the childbearing years. The management of mental illness during pregnancy and lactation is a particularly complex clinical situation. The cornerstone of such a clinical decision is a completion of an assessment of the risks of the illness vs the risks of treatment. The following article reviews the factors influencing infant outcome and outlines the essential elements of the process of determining risk for the use of psychotropics in women during pregnancy and lactation. As the available data rapidly change, the facets of the risk benefit assessment are consistent and often the issue of specific medication is decided by prior history and exposure.