Observers can voluntarily shift their psychometric functions without losing sensitivity

Psychometric sensory discrimination functions are usually modeled by cumulative Gaussian functions with just two parameters, their central tendency (μ) and their slope (1/σ). These correspond to Fechner's "constant" and "variable" errors, respectively. Fechner pointed out that even the constant error could vary over space and time and could masquerade as variable error. We wondered whether observers could deliberately introduce a constant error into their performance without loss of precision. In three-dot vernier and bisection tasks with the method of single stimuli, observers were instructed to favour one of the two responses when unsure of their answer. The slope of the resulting psychometric function was not significantly changed, despite a significant change in central tendency. Similar results were obtained when altered feedback was used to induce bias. We inferred that observers can adopt artificial response criteria without any significant increase in criterion fluctuation. These findings have implications for some studies that have measured perceptual "illusions" by shifts in the psychometric functions of sophisticated observers.     

Elevated suicide rates at high altitude: sociodemographic and health issues may be to blame

Suicide rates are higher at high altitudes; some hypothesize that hypoxia is the cause. We examined 8,871 suicides recorded in 2006 in 15 states by the National Violent Death Reporting System, with the victim's home county altitude determined from the National Elevation Dataset through FIPS code matching. We grouped cases by altitude (low<1000m; middle=1000-1999m; high≥2000m). Of reported suicides, 5% were at high and 83% at low altitude, but unadjusted suicide rates per 100,000 population were higher at high (17.7) than at low (5.7) altitude. High and low altitude victims differed with respect to race, ethnicity, rural residence, intoxication, depressed mood preceding the suicide, firearm use and recent financial, job, legal, or interpersonal problems. Even after multivariate adjustment, there were significant differences in personal, mental health, and suicide characteristics among altitude groups. Compared to low altitude victims, high altitude victims had higher odds of having family or friends report of a depressed mood preceding the suicide (OR 1.78; 95%CI:1.46-2.17) and having a crisis within 2weeks before death (OR 2.00; 95%CI:1.63-1.46). Suicide victims at high and low altitudes differ significantly by multiple demographic, psychiatric, and suicide characteristics; these factors, rather than hypoxia or altitude itself, may explain increased suicide rates at high altitude.     

Examining classification criteria: a comparison of three cut score methods

This study compared 3 different methods of creating cut scores for a screening instrument, T scores, receiver operating characteristic curve (ROC) analysis, and the Rasch rating scale method (RSM), for use with the Behavioral and Emotional Screening System (BESS) Teacher Rating Scale for Children and Adolescents (Kamphaus & Reynolds, 2007). Using the BESS norm data set, we compared the methods across 7 classification indices. Additional information about accuracy was used with a subset of children who had been given a prior diagnosis for selected disorders. The results showed that the methods were generally in concordance, with similarities identified across methods. RSM and ROC analysis methods performed similarly, with both methods identifying the same optimal cut-point. The method based on T scores appeared to be more conservative, identifying a lower cut score as optimal.     

The neural substrates associated with inattentional blindness

Inattentional blindness is the failure to perceive salient stimuli presented at unattended locations. Whereas the behavioral manifestation of inattentional blindness has been investigated, the neural basis of this phenomenon has remained elusive. In the current study, event-related fMRI was used to identify the neural substrates associated with inattentional blindness. During central fixation, participants named colored digits presented at a peripheral location. On a subset of trials, an unexpected checkerboard circle (the critical stimulus) was presented at the same eccentricity along with the colored digits (a post-scan questionnaire assessed participants’ awareness of the critical stimulus). Neural activity during inattentional blindness was observed in the prefrontal cortex. Together with previous findings, these results call into question the widespread view that activity in the prefrontal cortex reflects conscious processing.     

Cognitive culture: theoretical and empirical insights into social learning strategies

Research into social learning (learning from others) has expanded significantly in recent years, not least because of productive interactions between theoretical and empirical approaches. This has been coupled with a new emphasis on learning strategies, which places social learning within a cognitive decision-making framework. Understanding when, how and why individuals learn from others is a significant challenge, but one that is critical to numerous fields in multiple academic disciplines, including the study of social cognition.     

Visual threat detection during moderate- and high-intensity exercise

The aim of the study was to assess performance on a visual threat-detection task during concurrently performed vigorous exercise on a cycle ergometer. Thirty (15 female) participants completed a baseline condition of seated rest and then moderate- and high-intensity exercise. Moderate- and high-intensity exercise conditions were completed on the 2nd day in a counterbalanced order. During each exercise condition, participants responded to 3 × 3 picture matrices (256 trials in each condition) that contained discrepant fear-relevant and discrepant fear-irrelevant pictures (?hman, Flykt, & Esteves, 2001). Response accuracy was significantly greater, and reaction time was significantly faster, during moderate- and high-intensity exercise compared with the rest condition (ps < .001). The discrepant fear-relevant matrix type was detected significantly more accurately than a discrepant fear-irrelevant matrix (p < .001). The discrepant fear-relevant matrix was detected significantly faster than all other matrix types (p < .001). These results suggest that exercise at a moderate and high intensity may enhance the efficiency of visual detection of both threatening and nonthreatening targets.     

Pulling the finger off disrupts agency, embodiment and peripersonal space

For this experiment a visual illusion was created in which the participant's finger looked and felt as though it was being stretched to twice its normal length until it snapped and the tip came off. It was then stabbed with virtual weapons while skin conductance was measured. Sometimes the fingertip moved under the participant's own control and sometimes it moved independently. Curiously, detaching the tip of the finger destroyed the underlying ownership for the remaining stump as well as for the tip itself, even when the tip was under participants' control. These results have implications for theories of agency, embodiment, and tool-use.     

An inductive exploration of the social effectiveness construct space

ABSTRACT There is no agreement regarding the nature or number of dimensions that make up the social effectiveness domain. We inductively explore the relationships between a set of social effectiveness measures with the intention of identifying an initial set of dimensions. An exploratory factor analysis of the Social Competence Inventory (SCI, Schneider, 2001 ) resulted in the identification of four factors: Social Potency, Social Appropriateness, Social Emotional Expression, and Social Reputation. A joint factor analysis between the SCI and a set of extant measures resulted in the identification of the same four factors. A fifth factor emerged when a set of scales from an emotional intelligence measure was included in the analysis, suggesting that emotional intelligence is not captured within the common factor space defined by measures of social effectiveness. This study represents a first step in the establishment of a set of common social effectiveness dimensions.     

Diagnostic accuracy of the MMPI-2 Malingering Discriminant Function Index in the detection of malingering among inmates

The MMPI-2 Malingering Discriminant Function Index (M-DFI) was designed to detect malingerers educated about MMPI-2 validity indicators. However, given current attorney practices, the clinical utility of the M-DFI lies in its ability to detect examinees who are cautioned about the indicators. In this study, we compared 45 inmate simulators cautioned to avoid detection on the MMPI-2 with 46 psychiatric inmates who completed the MMPI-2 under standard instructions. Logistic regression analyses indicated that although the M-DFI performed better than several individual indicators, results were mixed for combinations of indicators, and the M-DFI did not outperform different sets of existing indicators. These findings support existing strategies to detect malingering on the MMPI-2. We discuss considerations concerning the clinical applicability of M-DFI.