Performance variability is related to change in cognition: evidence from the Victoria Longitudinal Study

Performance variability across repeated task administrations may be an important indicator of age-related cognitive functioning. In the present investigation, the authors examined whether age differences and change in inconsistency were related to 6-year (3 occasion) cognitive change. Inconsistency scores were computed from 4 reaction time tasks performed by 446 older adults (54-89 years). Replicating previous cross-sectional results, greater inconsistency was observed for older participants even after controlling for differences in response speed. New longitudinal results demonstrated (a) associations between inconsistency at baseline measurement and 6-year change in cognitive performance; (b) longitudinal change in inconsistency; and (c) intraindividual covariation between 6-year change in inconsistency and 6-year change in level of cognitive function. These findings support the view that performance variability serves as a marker of cognitive aging.     

Seeing big things: overestimation of heights is greater for real objects than for objects in pictures

In six experiments we demonstrate that the vertical-horizontal illusion that is evoked when viewing photographs and line drawings is relatively small, whereas the magnitude of this illusion when large objects are viewed is at least twice as great. Furthermore, we show that the illusion is due more to vertical overestimation than horizontal underestimation. The lack of a difference in vertical overestimation between pictures and line drawings suggests that vertical overestimation in pictures depends solely on the perceived physical size of the projection on the picture surface, rather than on what is apparent about an object's represented size. The vertical-horizontal illusion is influenced by perceived physical size. It is greater when viewing large objects than small pictures of these same objects, even when visual angles are equated.     

Stimulus Equivalence and The Blocking Effect

The Psychological Record - The purpose of this experiment was to examine the blocking effect within the context of a stimulus equivalence paradigm. Ten subjects were provided with a prior history...     

Association Between Employment and Sexual Risk-Taking Behaviors Among Public High School Adolescents

We examined the relationship between adolescent after school and weekend employment and sexual intercourse behavior in a cross-sectional sample of public high school students in South Carolina. The CDC Youth Risk Behavior Survey was used to secure usable data from 4,800 subjects. Thirty-nine percent of the sample worked at a job for pay during the academic year of the study. The majority of all race/gender groups reported having sexual intercourse in their lifetime and during the past 3 months prior, with the exception of Caucasian females. For Caucasian males employment ranging from 1-5 to 31+ hours per week was associated with sexual risk-taking. Caucasian female employment was associated with sexual risk-taking at 16-20 and 21-25 hours of work per week. For African American males, the relationship between employment and sexual risk-taking was evidenced at the 1-5 and 26-30 hours of work per week levels. Similar trends were determined for Caucasians (males and females) regarding sexual intercourse in the past 3 months prior and working for pay during the academic year. Youth working above 10 hours per week during high school may have an increased risk for unintended pregnancy and sexually transmitted infections, including HIV.     

Why scientists valuep values

According to almost any approach to statistical inference, attained significance levels, orp values, have little value. Despite this consensus among statistical experts,p values are usually reported extensively in research articles in a manner that invites misinterpretation. In the present article, I suggest that the reasonp values are so heavily used is because they provide information concerning the strength of the evidence provided by the experiment. In some typical hypothesis testing situations, researchers may be interested in the relative adequacy of two different theoretical accounts: one that predicts no difference across conditions, and another that predicts some difference. The appropriate statistic for this kind of comparison is the likelihood ratio,P(D|M ₀)/P(D|M ₁), whereM ₀ andM ₁ are the two theoretical accounts. Large values of the likelihood ratio provide evidence thatM ₀ is a better account, whereas small values indicate thatM1 is better. I demonstrate that, under some circumstances, thep value can be interpreted in the same manner as the likelihood ratio. In particular, forZ,t, and sign tests, the likelihood ratio is an approximately linear function of thep value, with a slope between 2 and 3. Thus, researchers may reportp values in scientific communications because they are a proxy for the likelihood ratio and provide the readers with information about the strength of the evidence that is not otherwise available.     

Temporal integration and segregation of brief visual stimuli: Patterns of correlation in time

Two brief sequential displays separated by a brief interstimulus interval (ISI) are often perceived as a temporally integrated unitary configuration. The probability of temporal integration can be decreased by increasing the ISI or (counterintuitively) by increasing stimulus duration. We tested three hypotheses of the relative contributions of stimulus duration and ISI to the breakdown of temporal integration (the storage, processing, and temporal correlation hypotheses). In the first of two experiments, stimulus duration and ISI were varied factorially, and estimates of temporal integration were obtained with a form-part integration task. The second experiment was a replication of the first at two levels of stimulus intensity. The outcomes were inconsistent with the storage and processing options, but confirmed predictions from the temporal correlation hypothesis. Whether two sequential stimuli are perceived as temporally integrated or disjoint depends not on the availability of visible persistence, but on the emergence of a neural code that is based on the temporal correlation between the two visual responses.     

The nature of standard control in children's matching-to-sample

In Experiment I, six preschool-aged children were given matching-to-sample training with two figures in which they were required to choose one of two comparison stimuli that was identical in shape to the standard stimulus. Following this training, they were given intermittent test trials in which a novel stimulus figure was substituted for the previously correct comparison stimulus. Five of the six subjects consistently chose the substituted stimulus during test trials. Experiment II replicated the findings of Experiment I with three other preschool-aged children. Experiment II also provided controls for the possibility that the subjects of Experiment I were selecting the substituted stimulus because of its novelty. The investigators concluded that eight of the nine subjects were exhibiting the type of control described by Berryman, Cumming, Cohen, and Johnson (1965) as S-delta responding.