Using just noticeable differences to interpret test scores

This study explored the value of obtaining a just noticeable difference (JND) for a test--the difference in scores needed before observers detect a difference in examinees' behavior--as a means of interpreting the practical meaning of scores. Classical psychophysical methods were adapted and applied to the scores of foreign teaching assistants (TAs) on an achievement test, the Test of Spoken English (TSE), and the ratings for English proficiency that the TAs received from their students. The JND for the TSE scores was substantial, as large as the standard deviation of the scores and much larger than the standard error of measurement and guidelines for the d index of effect size for mean differences, suggesting that both sets of standards may highlight score differences that are not practically significant. This study demonstrates the applicability of JNDs for evaluating scores on educational and psychologists' tests.     

Subjective equality and just noticeable differences in body-size judgments by obese persons

Body-size estimates by obese and normal-weight subjects were compared using two different procedures with a TV-video methodology. In the continuous method subjects adjusted an image larger or smaller until they judged a correct TV-image had been achieved. In the second procedure the method of constant stimuli was used wherein values corresponding to the point of subjective equality (PSE) and difference threshold (DL) were determined. No differences between obese and normal-weight subjects were obtained with these procedures. On the continuous task subjects slightly underestimated body size and were more accurate on descending trials where they adjusted the size of the image downwards. With the second procedure, an average PSE of -.62% was obtained, with an average DL = 7.27%. Different PSE values were obtained when subjects were judging whether their image was distorted too wide or too thin. Data from the two procedures are compared and ramifications for the study of body size are discussed.     

Intentions in teasing: when "just kidding" just isn't good enough

Teasing is ambiguous. Although the literal content of a tease is, by definition, negative, seldom do teasers intend for their tease to be taken literally. Toward this aim, teasers often attempt to mitigate the negative surface content of the tease by communicating via gesture, facial expression, or tone of voice that they are "just kidding." The research presented here suggests that such attempts often fall on deaf ears. Despite teasers' attempts to mitigate the tease, targets are often unaware of--and unmoved by--the teaser's benign intentions. As a result, teasers and targets systematically differ in their perceptions of teasing: Although it is often seen as innocent and playful by the teaser, it tends to be construed as considerably more malicious by the target.     

The development of perceptual averaging: learning what to do,not just how to do it

The mature visual system condenses complex scenes into simple summary statistics (e.g., average size, location, orientation, etc.). However, children, often perform poorly on perceptual averaging tasks. Children's difficulties are typically thought to represent the suboptimal implementation of an adult‐like strategy. This paper examines another possibility: that children actually make decisions in a qualitatively different way to adults (optimal implementation of a non‐ideal strategy). Ninety children (6–7, 8–9, 10–11 years) and 30 adults were asked to locate the middle of randomly generated dot‐clouds. Nine plausible decision strategies were formulated, and each was fitted to observers' trial‐by‐trial response data (Reverse Correlation). When the number of visual elements was low (N < 6), children used a qualitatively different decision strategy from adults: appearing to “join up the dots” and locate the gravitational center of the enclosing shape. Given denser displays, both children and adults used an ideal strategy of arithmetically averaging individual points. Accounting for this difference in decision strategy explained 29% of children's lower precision. These findings suggest that children are not simply suboptimal at performing adult‐like computations, but may at times use sensible, but qualitatively different strategies to make perceptual judgments. Learning which strategy is best in which circumstance might be an important driving factor of perceptual development.     

Analytical methods in the theory of psychophysical discrimination I: Inequalities, convexity and integration of just noticeable differences

We re-examine the theoretical status of Fechner's Mathematical Auxiliary Principle [Fechner, G. T. (1889). Elemente der psychophysik. Leipzig: Breitkopf und Härtel] which underlies Fechner's method of constructing a sensory scale by integrating just noticeable differences (jnds). That “Principle” has been roundly criticized [Luce, R. D., & Edwards, W. (1958). The derivation of subjective scales from just noticeable differences. Psychological Review, 65, 227-237] as being inconsistent with the very basis of Fechner's psychophysical theory, and indeed this is the case. In important papers Pfanzagl [(1962). Über die stochastische Fundierung des psychophysischen Gesetzes (On the stochastic foundations of the psychophysical law). Biometrische Zeitschrift, 4, 1-14] and Krantz [(1971). Integration of just noticeable differences. Journal of Mathematical Psychology, 8, 591-599] resurrected Fechner's method; their analysis showed that the sensory scale could be written as the limit of a sequence of integrals, each of the form suggested by the auxiliary principle. In this work, we investigate the properties of a typical member of the Krantz-Pfanzagl sequence of integrals; we do so with the view to obtaining useful approximations to the true scale. Weber's inequality [Falmagne, J.-Cl. (1977). Note: Weber's inequality and Fechner's problem. Journal of Mathematical Psychology, 16, 267-271] plays an important role in our developments. That inequality, and other inequalities of a similar nature, allows us to place bounds on the error incurred by approximating a true scale u by an integral of jnds. Under appropriate conditions these bounds are sufficiently tight that the relative error is very small over the entire stimulus domain. We illustrate our theoretical results with a number of examples.     

To "do the right thing" or to "just do it": locomotion and assessment as distinct self-regulatory imperatives

An integrated series of studies investigated 2 functional dimensions of self-regulation referred to as assessment and locomotion (E. T. Higgins and A. W. Kruglanski, 1995). Assessment constitutes the comparative aspect of self-regulation that critically evaluates alternative goals or means to decide which are best to pursue and appraises performance. Locomotion constitutes the aspect of self-regulation concerned with movement from state to state, including commitment of psychological resources to initiate and maintain such movement. Two separate scales were developed to measure individual differences in these tendencies. Psychometric work attested to the scales' unidimensionality, internal consistency, and temporal stability. The authors found that (a) locomotion and assessment are relatively independent of each other, (b) both are needed for self-regulatory success, and (c) each relates to distinct task orientations and motivational emphases.     

Not "just" a coincidence: frontal-striatal interactions in working memory and interval timing

The frontal cortex and basal ganglia play central roles in working memory and in the ability to time brief intervals. We outline recent theoretical and empirical work to suggest that working memory and interval timing rely not only on the same anatomic structures, but also on the same neural representation of a specific stimulus. Specifically, cortical neurons may fire in an oscillatory fashion to form representations of stimuli, and the striatum (a basal ganglia structure) may detect those patterns of cortical firing that occur co-incident to important events. Information about stimulus identity can be extracted from which cortical neurons are involved in the representation, and information about duration can be extracted from their relative phase. The principles derived from these biologically based models also fit well with a family of behaviourally based models that emphasise the importance of time in many working memory phenomena.