Ecological relevance of stereopsis in one-handed ball-catching

The aim of this study was to compare one-handed catching performance between catchers with high (n = 10) and low (n = 10) binocular depth vision or stereopsis. In two sessions of 90 trials, tennis balls were projected at three different velocities towards the subject's shoulder region. Participants with good stereopsis were more successful, although the difference in number of correct catches fell short of significance. More specifically, catchers with low stereopsis made more temporal errors, but no differences in spatial errors. As the velocity of the ball increased, the initiation of the catch was delayed and catching performance decreased. The finding that stereopsis affected timing of the catch challenges the 'monocular tau hypothesis' in the control of interceptive timing, while the velocity effect shows that the act of catching a ball is not initiated at a constant time-to-contact.     

Cost–benefit and distributional analyses of accessory stimuli

Accessory stimuli (AS) are task-irrelevant events (typically an auditory tone) that speed reaction time (RT). With two conditions (AS-present, AS-absent) it is unclear whether AS-presence causes benefits or AS-absence causes costs, possibly due to the expectancy violations. The current study added a third condition where AS were absent in blocks and not expected (pure blocks); in other blocks, AS occurred with a probability of 0.5 (mixed blocks), allowing cost-benefit analysis comparing AS-absent RTs in pure and mixed blocks. Results demonstrated RTs were slower when AS were absent, regardless of whether the absence occurred in a mixed block or a pure block, suggesting AS do provide a benefit to RT. Additionally, AS-facilitation across the RT distribution was analysed using cumulative distribution frequencies and ex-Gaussian parameter estimation. Both provided converging evidence that AS-facilitation increases towards the slower end of the RT distribution. The implications for the utility of AS paradigms are discussed.     

<Literal>flankr</Literal>: An R package implementing computational models of attentional selectivity

The Eriksen flanker task (Eriksen and Eriksen, Perception & Psychophysics, 16, 143–149, 1974) is a classic test in cognitive psychology of visual selective attention. Two recent computational models have formalised the dynamics of the apparent increasing attentional selectivity during stimulus processing, but with very different theoretical underpinnings: The shrinking spotlight (SSP) model (White et al., Cognitive Psychology, 210–238, 2011) assumes attentional selectivity improves in a gradual, continuous manner; the dual stage two phase (DSTP) model (Hübner et al., Psychological Review, 759–784, 2010) assumes attentional selectivity changes from a low- to a high-mode of selectivity at a discrete time-point. This paper presents an R package—flankr—that instantiates both computational models. flankr allows the user to simulate data from both models, and to fit each model to human data. flankr provides statistics of the goodness-of-fit to human data, allowing users to engage in competitive model comparison of the DSTP and the SSP models on their own data. It is hoped that the utility of flankr lies in allowing more researchers to engage in the important issue of the dynamics of attentional selectivity.     

Effects of peripheral immune activation on social behavior and adrenocortical activity in aggressive mice: Genotype-environment interactions

To explore genetic-developmental differences in the biobehavioral effects of induced illness, males from two lines of mice selectively bred for high or low levels of aggressive behavior were injected with endotoxin (Escherichia coli, LPS: 0.25 mg/kg, 1.25 mg/kg, or 2.5 mg, i.p.) or saline. Body temperature, weight, and locomotor activity were monitored immediately before and 8 and 24 hr after injection. Twenty-four hours after injection, social behaviors were assessed in a 10-min dyadic test, and hypothalamus, spleen, and serum were collected. In both lines, endotoxin treatment increased behavioral immobility ("freezing") and decreased social exploration. Other effects showed line differences: Males from the high-aggressive line had a lower threshold to endotoxin-induced effects on body temperature, weight loss, spleen weight, and corticosterone. Social reactivity (startle response to mild social investigation) increased in the high-aggressive line and decreased in the low-aggressive line after treatment. In the high-aggressive line only, endotoxin decreased attack frequency and increased latency to attack. The interactions between selected line (genotype) and endotoxin treatment (environment) demonstrate that genetic-developmental differences in social and aggressive behavior may indicate the extent to which immune stimuli (e.g., bacteria, viruses, cytokines) function as "biobehavioral stressors." Aggr. Behav. 23:93–105, 1997.© 1997 Wiley-Liss, Inc.     

CDF-XL: computing cumulative distribution functions of reaction time data in Excel

In experimental psychology, central tendencies of reaction time (RT) distributions are used to compare different experimental conditions. This emphasis on the central tendency ignores additional information that may be derived from the RT distribution itself. One method for analysing RT distributions is to construct cumulative distribution frequency plots (CDFs; Ratcliff, Psychological Bulletin 86:446–461, 1979). However, this method is difficult to implement in widely available software, severely restricting its use. In this report, we present an Excel-based program, CDF-XL, for constructing and analysing CDFs, with the aim of making such techniques more readily accessible to researchers, including students (CDF-XL can be downloaded free of charge from the Psychonomic Society’s online archive). CDF-XL functions as an Excel workbook and starts from the raw experimental data, organised into three columns (Subject, Condition, and RT) on an Input Data worksheet (a point-and-click utility is provided for achieving this format from a broader data set). No further preprocessing or sorting of the data is required. With one click of a button, CDF-XL will generate two forms of cumulative analysis: (1) “standard” CDFs, based on percentiles of participant RT distributions (by condition), and (2) a related analysis employing the participant means of rank-ordered RT bins. Both analyses involve partitioning the data in similar ways, but the first uses a “median”-type measure at the participant level, while the latter uses the mean. The results are presented in three formats: (i) by participants, suitable for entry into further statistical analysis; (ii) grand means by condition; and (iii) completed CDF plots in Excel charts.     

Subtyping adolescents with bulimia nervosa

Cluster analyses of eating disorder patients have yielded a "dietary-depressive" subtype, typified by greater negative affect, and a "dietary" subtype, typified by dietary restraint. This study aimed to replicate these findings in an adolescent sample with bulimia nervosa (BN) from a randomized controlled trial and to examine the validity and reliability of this methodology. In the sample of BN adolescents (N=80), cluster analysis revealed a "dietary-depressive" subtype (37.5%) and a "dietary" subtype (62.5%) using the Beck Depression Inventory, Rosenberg Self-Esteem Scale and Eating Disorder Examination Restraint subscale. The "dietary-depressive" subtype compared to the "dietary" subtype was significantly more likely to: (1) report co-occurring disorders, (2) greater eating and weight concerns, and (3) less vomiting abstinence at post-treatment (all p's<.05). The cluster analysis based on "dietary" and "dietary-depressive" subtypes appeared to have concurrent validity, yielding more distinct groups than subtyping by vomiting frequency. In order to assess the reliability of the subtyping scheme, a larger sample of adolescents with mixed eating and weight disorders in an outpatient eating disorder clinic (N=149) was subtyped, yielding similar subtypes. These results support the validity and reliability of the subtyping strategy in two adolescent samples.     

Family criticism and self-starvation: a study of expressed emotion

The measure Expressed Emotion (EE) has been established as an exceptionally useful indicator of relapse in people with schizophrenia and depression. EE is now also being applied more broadly for the investigation of other disorders. EE is usually rated by conducting the Camberwell Family Interview, i.e. in the course of separate individual interviews with the relatives of the symptomatic individuals. This paper reports the rating of EE in adolescents with eating disorders within a semi-structured family schedule - the Standardized Clinical Family Interview. Consecutive referrals for eating disorders were assessed prior to family therapy and again at regular intervals during therapy. EE ratings for this sample, the prognostic value of EE, and the changes in EE that took place during the course of therapy are presented and their clinical implications discussed. The findings suggest that even low levels of Critical Comments from the parents to the anorexic adolescent are associated with continuing symptoms.     

Subtypes of Adaptive and Maladaptive Perfectionism in Anorexia Nervosa: Associations with Eating Disorder and Affective Symptoms

Perfectionism is hypothesized to contribute to the etiology of anorexia nervosa (AN). However, there is little research regarding whether individuals with AN can be classified according to maladaptive (e.g., evaluative concerns) and adaptive (e.g., high personal standards) facets of perfectionism that predict distinct outcomes and might warrant different intervention approaches. In this study, a latent profile analysis was conducted using data from adults with AN (n?=?118). Frost Multidimensional Perfectionism Scale (Frost et al. Cognitive Therapy and Research, 14(5), 449–46, 1990) subscales were used to identify subgroups differing according to endorsed perfectionism features (e.g., adaptive and maladaptive perfectionism). Generalized linear models were used to compare subgroups on eating disorder and affective symptoms measured through questionnaire and ecological momentary assessment. Four subgroups were identified: (a) Low Perfectionism; (b) High Adaptive and Maladaptive Perfectionism; (c) Moderate Maladaptive Perfectionism; and (d) High Maladaptive Perfectionism. Subgroups differed on overall eating disorder symptoms (p?<?.001), purging (p?=?.005), restrictive eating (p?<?.001), and body checking (p?<?.001) frequency, depressive (p?<?.001) and anxiety (p?<?.001) symptoms, and negative (p?=?.001) and positive (p?<?.001) affect. The Low Perfectionism group displayed the most adaptive scores and the Moderate and High Maladaptive Perfectionism groups demonstrated the most elevated clinical symptoms. The High Adaptive and Maladaptive Perfectionism group demonstrated low affective disturbances, but elevated eating disorder symptoms. Results support the clinical significance of subtyping according to perfectionism dimensions in AN. Research is needed to determine if perfectionism subtyping can enhance individualized treatment targeting in AN.