Assessing item-feature effects with item response tree models

Recent applications of item response tree models demonstrate that this model class is well suited to detect midpoint and extremity response style effects in both attitudinal and personality measurements. This paper proposes an extension of this approach that goes beyond measuring response styles and allows us to examine item-feature effects. In a reanalysis of three published data sets, it is shown that the proposed extension captures item-feature effects across affirmative and reverse-worded items in a psychological test. These effects are found to affect directional responses but not midpoint and extremity preferences. Moreover, accounting for item-feature effects substantially improves model fit and interpretation of the construct measurement. The proposed extension can be implemented readily with current software programs that facilitate maximum likelihood estimation of item response models with missing data.     

Toward a dimensional and psychometrically-informed approach to conceptualizing psychopathology

Most modern research on psychopathology is framed by the categorical model of mental disorders embodied in the Diagnostic and statistical manual of mental disorders, 4th edition (DSM-IV; American Psychiatric Association, 1994). Nevertheless, the categorical model of the DSM is incompatible with robust empirical observations about psychopathological variation, such as the tendency for multiple, putatively distinct mental disorders to occur in the same persons. The goal of this invited essay is to outline a potential alternative to the DSM's categorical approach: a dimensional and psychometrically-informed approach to conceptualizing and studying psychopathology. We discuss the advantages of the dimensional approach, some modern statistical technologies that can be recruited in the service of the dimensional approach, and ways of integrating the dimensional approach with a behavioral approach to psychopathology assessment and research.     

The living legacy of the Harvard Pigeon Lab: quantitative analysis in the wide world

From the Harvard Pigeon Lab of the 1960s arose a behavior-analytic approach that was quantitative and rigorous, rooted in Herrnstein's matching law. Researchers modified the matching law to describe choice behavior in a variety of different settings and examined its relations with other quantitative models. Beginning in the early 1970s, researchers began using the Harvard Pigeon Lab's quantitative framework to study in the laboratory specific aspects of the world outside the laboratory. Much of this work concerned investigations of self-control-choice of a larger, more delayed reinforcer over a smaller, less delayed reinforcer. Experiments using a quantitative framework derived from the matching law have also been conducted outside the laboratory; however, these have been far less frequent. Current and future researchers will benefit the field by devising new, creative ways to investigate the matching law and related quantitative models outside the laboratory. Such research can help to demonstrate the validity of these models as basic principles of behavior, can enhance public opinion of and rewards for such research, and can stimulate further development of the Harvard Pigeon Lab's quantitative approach by using that approach with new variables.     

The Children of Mothers with Eating Disorders

There is good evidence that children of parents with psychological disorders are themselves at increased risk of disturbances in their development. Although there has been considerable research on a variety of disorders such as depression and alcohol, research on the children of parents with eating disorders has been relatively recent. This paper aims to review the evidence and covers a number of areas, including genetic factors, pregnancy, the perinatal and postpartum period, infancy, and the early years of life, focusing on feeding and mealtimes, general parenting functions, and growth. This is followed by a consideration of psychopathology in the children, parental attitudes to children's weight and shape, and adolescence. What is clear is that although there are numerous case reports and case series, the number of systematic controlled studies is relatively small, and almost nothing has been written about the children of fathers with eating disorders. What is evident from the available evidence is that children of mothers with eating disorders are at increased risk of disturbance, but that the risk depends on a variety of factors, and that difficulties in the children are far from invariable. The paper concludes by summarizing five broad categories of putative mechanisms, based on the evidence to date, by which eating disturbance in parents can influence child development.     

Shifts in the psychometric function and their implications for models of timing

This study examined how two models of timing, scalar expectancy theory (SET) and learning to time (LeT), conceptualize the learning process in temporal tasks, and then reports two experiments to test these conceptualizations. Pigeons responded on a two-alternative free-operant psychophysical procedure in which responses on the left key were reinforceable during the first two, but not the last two, quarters of a 60-s trial, and responses on the right key were reinforceable during the last two, but not the first two, quarters of the trial. In Experiment 1 three groups of birds experienced a difference in reinforcement rates between the two keys only at the end segments of the trial (i.e., between the first and fourth quarters), only around the middle segments of the trial (i.e., between the second and third quarters), or in both end and middle segments. In Condition 1 the difference in reinforcement rate favored the left key; in Condition 2 it favored the right key. When the reinforcement rates differed in the end segments of the trial, the psychometric function--the proportion of right responses across the trial--did not shift across conditions; when it occurred around the middle of the trial or in both end and middle segments, the psychometric function shifted across conditions. Experiment 2 showed that the psychometric function shifts even when the overall reinforcement rate for the two keys is equal, provided the rates differ around the middle of the trial. This pattern of shifts of the psychometric function is inconsistent with SET. In contrast, LeT provided a good quantitative fit to the data.