Additional rules for the transformed up-down method in psychophysics

In a classic paper, Levitt (1971) described an adaptive procedure for estimating points on the psychometric function known as thetransformed up-down method. Levitt discussed the assumptions of the method and presented a brief table with simple rules that converge to a few different points on the psychometric function. Levitt’s original table contains only the simplest rules, and sparsely covers the range of the psychometric function. This paper provides a table with previously unpublished rules which cover the range of the psychometric function at 5% intervals. There is a brief review of the major issues in adaptive testing. Technical issues such as the mean length and logical construction of the new rules are discussed.     

The importance of being upright: Use of environmental and viewer-centered reference frames in shape discriminations of novel three-dimensional objects

We investigated the frame of reference that people use to make shape discriminations when their heads are either upright or tilted. Observers madesame-different judgments of pairs of novel threedimensional objects that were aligned along their length within the frontal-parallel plane and rotated in depth around an axis parallel to their own axes of elongation. The aligned objects were displayed vertically, tilted 45°, or horizontally with respect to the environmental upright, but the distance of each pair from the upright was irrelevant to resolving the angular disparity between the stimuli for thesame-different judgment. Nevertheless, when observers’ heads were upright, the time to encode the stimuli was a linear function of the distance of the stimuli from the environmental upright, whereas when observers’ heads were tilted 45°, encoding times for tilted and vertical stimuli did not differ and were faster than the times to encode horizontal stimuli. We interpreted these data to mean that observers either rotate or reference the top of an object to the environmental upright, and they can use either a gravitational or retinal reference frame to do so when either they or the objects are not upright.     

The impact of the transition to high school on the self-system and perceived social context of poor urban youth

Examined the effects of the normative school transition to senior high school (n=330) on the self-system and perceived school and peer social contexts of poor, black (n=83), European American (n=115), Latino (n=105), and Asian American (n=27) youth in the public school systems of three Eastern urban cities. The only negative effect of the school transition on the self-system was a decline in grade point average (GPA). Concurrently, the school transition was perceived to be associated with changes in the school and peer contexts. Across the transition, students reported increased disengagement from school (i.e., increased social support and extracurricular involvement) and increased engagement with peers (i.e., decreased daily hassles and increased involvement). These changes in the school and peer microsystems, like the changes in the self-system, were also common across race/ethnicity and gender. In addition, transition-associated school changes, and in particular changes in daily academic demands/hassles and involvement in school activities, were associated with changes in the academic dimensions of the self-system (i.e., academic efficacy expectations and GPA). Results and implications for preventive intervention are discussed within a developmental mismatch framework. This research was supported in part by grants from the National Institute of Mental Health (MH43084) and the Carnegie Corporation (B4850) awarded to Edward Seidman, J. Lawrence Aber, LaRue Allen, and Christina Mitchell. We express our appreciation to the children and schools whose cooperation made this study possible.     

Intensity resolution and subjective magnitude in psychophysical scaling

Several successful theories of psychophysical judgment imply that exponents of power functions in scaling tasks should covary with measures of intensity resolution such asd’ in the same tasks, whereas the prevailing metatheory of ideal psychophysical scaling asserts the independence of the two. In a direct test of this relationship, three prominent psychophysical scaling paradigms were studied: category judgment without an identification function, absolute magnitude estimation, and cross-modality matching with light intensity as the response continuum. Separate groups of subjects for each scaling paradigm made repeated judgments of the loudnesses of the pure tones that constituted each of two stimulus ensembles. The narrow- and wide-range ensembles shared six identical stimulus intensities in the middle of each set. Intensity resolution, as measured byd’-like distances, of these physically identical stimuli was significantly worse for the wide-range set for all three methods. Exponents of power functions fitted to geometric mean responses, and in magnitude estimation and cross-modality matching the geometric mean responses themselves, were also significantly smaller in the wide-range condition. The variation of power function exponents, and of psychophysical scale values, for stimulus intensities that were identical in the two stimulus sets with the intensities of other members of the ensembles is inconsistent with the metatheory on which modern psychophysical scaling practice is based, although it is consistent with other useful approaches to measurement of psychological magnitudes.     

A self-contained,regulated, burst-firing constant-current ac shock generator

A line- and load-regulated constant-current ac shock generator has been designed for animal behavior experiments. The self-contained unit has four operating modes, amplitude adjustment, and a leakage current detection circuit. A unique feature of this generator is that the good load regulation achieved by using a high-voltage source is preserved without such problems as arcing and high current density effects. Circuit schematics, along with a discussion of selected circuits, are included. Experimental data are presented to demonstrate the utility of the device.     

An IC up-down counter controller for a programmable attenuator

A simple up-down counter is used to control a programmable attenuator. This controller reduces the load on a minicomputer or other solid state circuitry when the attenuator is used for adaptive testing in psychoacoustics. Circuit diagrams for the controller and an auxiliary display driver are given, and some applications are discussed.     

Videotape as a replacement for the human observer in studies of nonhuman primate behavior

Bucknell University, Lewisburg, Pennsylvania 17837 For both field and laboratory studies of animal behavior, the availability of portable videotape recorders permits both improved techniques of observation and a means for permanent storage and rapid retrieval of observations. In some circumstances, videotape may be used to replace a human O. Evidence is presented that the behavior of at least one nonhuman primate commonly used in behavioral research, the squirrel monkey, differs when a human 0 is present from when behavior is recorded solely by videotape, even after 3 years of daily contact with human beings.     

Spatial summation and the dynamics of warmth sensation

Various areal extents of the forehead and back were thermally irradiated at various levels of intensity. For any areal extent, the degree of apparent warmth grows approximately as a power function of intensity level; the larger the area, the smaller the exponent of the power function. Two families of psychophysical functions, one for the forehead, the other for the back, both show that the power functions extrapolate to a point of convergence in the neighborhood of the threshold for pain and tissue impairment. The rules that govern spatial summation of warmth reveal themselvesin the two families. Intensity and area trade one for the other to preserve the same level of warmth. At faint sensation levels, reciprocity is the rule of trading; but with increasing sensation level, area makes a weaker and weaker relative contribution to warmth, and, as a result, it takes a larger and larger percentage change in area to offset a given percentage change in intensity.