The psychometric function: I. Fitting, sampling, and goodness of fit

The psychometric function relates an observer’s performance to an independent variable, usually some physical quantity of a stimulus in a psychophysical task. This paper, together with its companion paper (Wichmann & Hill, 2001), describes an integrated approach to (1) fitting psychometric functions, (2) assessing the goodness of fit, and (3) providing confidence intervals for the function’s parameters and other estimates derived from them, for the purposes of hypothesis testing. The present paper deals with the first two topics, describing a constrained maximum-likelihood method of parameter estimation and developing several goodness-of-fit tests. Using Monte Carlo simulations, we deal with two specific difficulties that arise when fitting functions to psychophysical data. First, we note that human observers are prone to stimulus-independent errors (orlapses). We show that failure to account for this can lead to serious biases in estimates of the psychometric function’s parameters and illustrate how the problem may be overcome. Second, we note that psychophysical data sets are usually rather small by the standards required by most of the commonly applied statistical tests. We demonstrate the potential errors of applying traditionalX ² methods to psychophysical data and advocate use of Monte Carlo resampling techniques that do not rely on asymptotic theory. We have made available the software to implement our methods.     

Delayed detection of tonal targets in background noise in dyslexia

Individuals with developmental dyslexia are often impaired in their ability to process certain linguistic and even basic non-linguistic auditory signals. Recent investigations report conflicting findings regarding impaired low-level binaural detection mechanisms associated with dyslexia. Binaural impairment has been hypothesized to stem from a general low-level processing disorder for temporally fine sensory stimuli. Here we use a new behavioral paradigm to address this issue. We compared the response times of dyslexic listeners and their matched controls in a tone-in-noise detection task. The tonal signals were either Huggins Pitch (HP), a stimulus requiring binaural processing to elicit a pitch percept, or a pure tone-perceptually similar but physically very different signals. The results showed no difference between the two groups specific to the processing of HP and thus no evidence for a binaural impairment in dyslexia. However, dyslexic subjects exhibited a general difficulty in extracting tonal objects from background noise, manifested by a globally delayed detection speed.     

Thinness and eating expectancies predict subsequent binge-eating and purging behavior among adolescent girls

One's expectancies for reinforcement from eating or from thinness are thought to represent summaries of one's eating-related learning history and to thus influence the development of binge-eating and purging behavior. In a 3-year longitudinal study, the authors tested this hypothesis and the hypothesis that binge eating also influences subsequent expectancy development. The authors used trajectory analysis to identify groups of middle school girls who followed different trajectories of binge eating, purging, eating expectancies, and thinness expectancies. Initial eating and thinness reinforcement expectancies identified girls whose binge eating and purging increased during middle school, and expectancies differentiated girls who began these problem behaviors from girls who did not. Initial binge-eating scores differentiated among eating expectancy developmental trajectories. The onset of most behaviors can be understood in terms of learned expectancies for reinforcement from these behaviors. The same model can be applied to the risk for eating disorders.     

Proactive, early screening to detect behaviorally at-risk students: Issues, approaches, emerging innovations, and professional practices

This article provides a review of current practices and tools used in the proactive screening of behaviorally at-risk students within the context of schooling. While there are many obstacles to the early detection of vulnerable students, some recent developments have helped make educators more receptive to early identification and prevention approaches. In addition to describing current best practices, this article reviews promising innovations in screening and early identification that the authors believe are worth considering and whose structural characteristics, required accommodations, and critical features may make them more acceptable to educational users. Implications for the training of school psychologists in the screening and early identification of high-risk students are reviewed and recommendations offered for future research.     

The role of frontal lobe functioning in the development of infant self-regulatory behavior.

In the last two decades, there has been tremendous growth in two fields of study related to human infant development: (1) the development of neural processes during the early postnatal years and (2) the development of self-regulatory behavior. In an attempt to stimulate research on the relation between early brain development and self-regulatory processes, several hypotheses pertaining to the role of frontal lobe functioning in the development of emotion regulation during infancy are proposed. The results of a study of the relation between frontal electroencephalographic (EEG) activity and emotional behavior of 21-month-old infants are reported. It was found that increases in frontal lobe activation were associated with increases in emotional arousal, while EEG activity recorded from the parietal region showed either a reciprocal pattern of activation or did not change as a function of level of emotional arousal. These results provide evidence for the specialized role of the frontal lobe in mediating emotional behavior during infancy.     

An Empirical Investigation of Critical Success Factors in the Personal Selling Process for Homogenous Goods

This study uses a Critical Success Factor approach to evaluate a representative set of 51 selling techniques with the intent of determining what techniques are more critical to sales success for salespeople who sell homogenous products than others and what techniques are associated with failure. A set of twelve techniques were identified that distinguished salespeople in the top decile from those in the bottom decile.     

A Quantitative Empirical Analysis of the Abstract/Concrete Distinction

This study presents original evidence that abstract and concrete concepts are organized and represented differently in the mind, based on analyses of thousands of concepts in publicly available data sets and computational resources. First, we show that abstract and concrete concepts have differing patterns of association with other concepts. Second, we test recent hypotheses that abstract concepts are organized according to association, whereas concrete concepts are organized according to (semantic) similarity. Third, we present evidence suggesting that concrete representations are more strongly feature‐based than abstract concepts. We argue that degree of feature‐based structure may fundamentally determine concreteness, and we discuss implications for cognitive and computational models of meaning.