Reaction time measures of backward masking

We employed both simple and choice reaction time (RT) paradigms in which the subjects were required to respond to 3.0 cycles per degree (c/d) square-wave gratings presented to one eye, while checkerboard masks were presented at various stimulus-onset asynchronies to the other eye. No masking was evident using the simple RT paradigm, but with the choice RT task, checkerboard masks presented to the contralateral eye of three subjects resulted in substantial decreases in response speed when the test preceded the mask by stimulus-onset asynchronies of 25 to 75 ms. Masks that contained lower fundamental spatial frequencies (1.0 c/d) than the target were more effective than masks containing fundamental spatial frequencies (6.0 c/d) higher than the target, while masks that contained fundamental components identical to those in the target (3.0 c/d) produced maximum masking. The results offer support for the sustained-transient theory of visual processing and validate RT as a technique for examining spatio-temporal factors in masking.     

Development of an automated performance test system for environmental and behavioral toxicology studies

In developing a menu of computerized performance tests for repeated-measures applications the metric properties of selected tests have been examined. Factors of chief concern have been stability and reliability, as well as the practical issue of the length of time it takes to achieve high levels of both. In this study, these factors, as well as predictive validity, are examined. 25 subjects were tested repeatedly (10 sessions) with 11 tests previously identified as "good" candidates for repeated-measures research in paper-and-pencil (marker test) versions. The 11 tests were administered concurrently in their traditional paper-and-pencil modes and newly implemented microcomputer-based versions, along with the Wechsler Adult Intelligence Scale (WAIS). Nine of the 11 microcomputer-based tests achieved stability. Reliabilities were generally high, with r greater than or equal to .77 for 3 min. of testing. Cross-correlations of microbased tests with traditional paper-and-pencil versions suggest equivalency between the test constructs in the different media. Correlations between six of the microbased subtests and the WAIS identified common variance, and these might comprise an efficient short (6 min.) battery of tests.     

Tonic immobility in the blue crab (Callinectes sapidus, Rathbun) its relation to threat of predation.

The tonic immobility. response in the blue crab (Callinectes sapidus, Rathbun) was investigated in a series of seven experiments. Although reported to be a powerful variable in other species, preinduction electric shock produced inconsistent increases in the duration of tonic immobility with the blue crab; Manipulations that were more directly relevant to the fear of predation had considerably greater effects than shock. Physical damage to the chelipeds, mirror image stimulation, and immobilization beneath artificial glass eyes all produced significant prolongation of the immobility episode; Crabs immobilized on a bed of sand rather than on a hard surface showed shorter immobility durations, suggesting that opportunity for escape is an important variable affecting the immobility reactionmthe present results support the contention that threat of predation is the organizing principle behind tonic immobility     

A computer program for determining optimal data transformations minimizing skew

A program is presented that solves for an optimal transformation of data that minimizes skew. Various possible transformations are represented by a function that depends upon a single parameter, λ. A process of iterative approximations is employed to find a value of λ that will transform the data so as to produce a third moment equal to zero. The transformation found by this process may be used as computed or used to indicate which of the commonly employed transformations will most adequately counteract skew. The use of this program in processing data before analysis of variance is discussed.     

PREFERRED CURRICULAR ACTIVITIES AND REDUCED PROBLEM BEHAVIORS IN STUDENTS WITH INTELLECTUAL DISABILITIES

This research examined the relation between students' preferences for curricular activities and the occurrence of problem and desirable behaviors in 3 students with moderate intellectual disabilities. Activity preference was determined with a systematic assessment procedure. Subsequently, the influence of activity preference on student behavior was evaluated using a reversal design. Results showed that preferred activities were associated with reduced levels of problem behavior and increased levels of desirable behaviors. The findings of this investigation contribute to the applied literature on activity preference and suggest directions for future research in the areas of curriculum design, preference, and curricular modifications as a viable behavior-management strategy.     

The conception of audience in Perelman and Isocrates: Locating the ideal in the real

The author compares two theoretical models which develop constructs of an ideal audience. Chaim Perelman's universal audience serves a methodological function within the New Rhetoric which provides for the examination of philosophical arguments on values. Implicit within the work of Isocrates is a competing image which asserts that the ideal audience is empowered by the conditions of argument to engage the advocate in discursive praxis to construct and embody a consensus on contingency-driven value debates. The author concludes that the concept of an ideal audience will be most valuable where interest in adherence to theses is less central than attendance to relationships born in and borne by discourse. Such a view has purchase within a constitutive view of rhetorical relations which asserts that the most useful role for argument is as an invitation to engagement. The situation of argumentation within a deontological ethics requires the partnership and participation of individuals in a mutually constructed discursive praxis.David Douglas Dunlap is a Doctoral Candidate in Speech Communication at Pennsylvania State University     

SAS procedures for approximate randomization tests

Approximate randomization tests are alternatives to conventional parametric statistical methods used when the normality and homoscedasticity assumptions are violated This article presents an SAS program that tests the equality of two means using an approximate randomization test This program can serve as a template for testing other hypotheses, which is illustrated by modifications to test the significance of a correlation coefficient or the equality of more than two means.     

Evaluation of prenatal androgen and ovarian secretions on receptivity in female and male rats

Offspring of rats infected daily from Day 16 through Day 20 of gestation with either 2 mg of testosterone propionate (TP) in .1 ml of sesame oil or oil alone were tested for sexual receptivity following injections of 3.3 microgram of estradiol benzoate (EB) and .5 mg of progesterone (P) beginning at 40, 80, or 120 days of age. At each age, neonatally gonadectomized males and females from TP-injected litters exhibited less receptivity than corresponding oil-injected controls. Prenatally androgenized females were similar to neonatally castrated oil-injected males at all ages. Ovarian implants from birth to 35 days of age significantly increased receptivity in neonatally castrated males and androgenized females. Increasing the age at which testing was initiated systematically reduced receptivity in all groups.     

Skew and internal consistency

The effects of skew on the standardized item alpha were examined with Monte Carlo techniques. Alphas computed from normal variables were compared with alphas from lognormal variables, ranks, and skewed versus normal Likert-type variables. The extent and direction of skew were varied, as was the size of the population interitem correlation (rho), the number of items, and the number of categories for Likert-type variables. Because the average interitem correlation affects alpha and skew affects the average interitem correlation, the effect of skew on the average interitem correlation also was examined. Results indicated that skew decreased the average interitem correlation and produced small decreases in alpha that were largest when skew was large, rho was small, items were skewed in opposite directions, and there were fewer items.     

Computing aspects of power for multiple regression.

Rules of thumb for power in multiple regression research abound. Most such rules dictate the necessary sample size, but they are based only upon the number of predictor variables, usually ignoring other critical factors necessary to compute power accurately. Other guides to power in multiple regression typically use approximate rather than precise equations for the underlying distribution; entail complex preparatory computations; require interpolation with tabular presentation formats; run only under software such as Mathmatica or SAS that may not be immediately available to the user; or are sold to the user as parts of power computation packages. In contrast, the program we offer herein is immediately downloadable at no charge, runs under Windows, is interactive, self-explanatory, flexible to fit the user's own regression problems, and is as accurate as single precision computation ordinarily permits.