Some tests of the interactive-activation model for word identification

Summary The interactive-activation model postulates (a) that activation at the letter level leads automatically to activation at the word level, (b) that the word-superiority effect reflects reactivation of letters by the word they spell, and (c) that subjects identify words on the basis of information obtained from separate letter-position channels. In the first two experiments, we showed words in upper, lower, or mixed case: the word-superiority effect was reduced when words were presented in mixed-case letters, presumably because extra-letter information is lost with mixed-case presentation; i.e., postulate (c) is wrong. The third experiment showed that when the letters of a word are rotated 180° subjects can identify the letters without producing a word-superiority effect; i.e., one of postulates (a) and (b) is wrong. In Experiments 4 and 5, we trained subjects to name words presented in inverted letters; training was more effective when subjects could exploit bigram information in addition to letter-channel information; i.e., reading inverted text is based on extra-letter-feature information, not on a general skill in rotating letters. Taken together, our data deny three of the interactive-activation model's major postulates. We offer some suggestions for future versions of the model. Electronic mail: Userid: MEWHORTD; Nodeid: QUCDN; Domain: BITNET     

The application of probit analysis to the results of mental tests

The application of the Müller-Urban constant process to item selection, as considered in a recent paper in this journal, is shown to be closely analogous to a method now in general use for the analysis of insecticidal and other toxicological tests. This method ofprobit analysis gives the maximum likelihood estimates of the unknown parameters and, with the aid of published tables, the necessary computations can be rapidly performed. The present paper contains an outline of the method and an illustration of the most convenient form of computations for use in analyses of psychometric data.     

The stochastic model of mental testing theory and an application

An axiomatization of mental test theory is presented. The presentation deals explicitly with the following concepts: true score, parallel forms, reliability, validity, and combined test score.This project was supported by the Office of Naval Research under Contract N6onr 270-(20) and by the National Science Foundation, Grant NSF G-642. Work now continued under Nonr 1858-(150) and NSF G-22889.     

A stochastic growth model applied to repeated tests of academic knowledge

In the course of the medical program at the University of Limburg, students complete a total of 24 progress tests, consisting of items drawn from a constant itembank. A model is presented for the growth of knowledge reflected by these results. The Rasch model is used as a starting point, but both ability and difficulty parameters are taken to be random, and moreover the logistic distribution is replaced by the normal. Both individual and group abilities are estimated and explained through simple linear regression. Application to real data shows that the model fits very well.     

Distribution-free tests of stochastic dominance for small samples

One variable is said to “stochastically dominate” another if the probability of observations smaller than x is greater for one variable than the other, for all x. Inferring stochastic dominance from data samples is important for many applications of econometrics and experimental psychology, but little is known about the performance of existing inferential methods. Through simulation, we show that three of the most widely used inferential methods are inadequate for use in small samples of the size commonly encountered in many applications (up to 400 observations from each distribution). We develop two new inferential methods that perform very well in a limited, but practically important, case where the two variables are guaranteed not to be equal in distribution. We also show that extensions of these new methods, and an improved version of an existing method, perform quite well in the original, unlimited case.     

Some tests of the Marr-Ullman model of movement detection

Several psychophysical experiments are described which test and uphold predictions derived from the Marr-Ullman model of movement detection. First, we demonstrate the existence of adaptation which is specific not merely to the direction of movement of an edge, but also to its contrast polarity. Second, it is shown that adaptation to a spatially homogeneous field whose luminance is modulated according to a temporal sawtooth waveform produces predictable changes in sensitivity to the movement of an edge; these changes, too, are specific to particular conjunctions of direction and edge polarity. Third, similar changes in sensitivity are demonstrated to occur when the luminance of an edge is physically perturbed at the moment of its displacement. Finally, it is shown that, as predicted, the sudden onset of an edge can itself give rise to a momentary impression of movement, the apparent direction of which depends upon the change in luminance that accompanies the onset of the edge.     

An accumulator model for responses and response times in tests based on the proportional hazards model

Latent trait models for responses and response times in tests often lack a substantial interpretation in terms of a cognitive process model. This is a drawback because process models are helpful in clarifying the meaning of the latent traits. In the present paper, a new model for responses and response times in tests is presented. The model is based on the proportional hazards model for competing risks. Two processes are assumed, one reflecting the increase in knowledge and the second the tendency to discontinue. The processes can be characterized by two proportional hazards models whose baseline hazard functions correspond to the temporary increase in knowledge and discouragement. The model can be calibrated with marginal maximum likelihood estimation and an application of the ECM algorithm. Two tests of model fit are proposed. The amenability of the proposed approaches to model calibration and model evaluation is demonstrated in a simulation study. Finally, the model is used for the analysis of two empirical data sets.     

Monte Carlo tests of the Rasch model based on scalability coefficients

For item responses fitting the Rasch model, the assumptions underlying the Mokken model of double monotonicity are met. This makes non‐parametric item response theory a natural starting‐point for Rasch item analysis. This paper studies scalability coefficients based on Loevinger's H coefficient that summarizes the number of Guttman errors in the data matrix. These coefficients are shown to yield efficient tests of the Rasch model using p‐values computed using Markov chain Monte Carlo methods. The power of the tests of unequal item discrimination, and their ability to distinguish between local dependence and unequal item discrimination, are discussed. The methods are illustrated and motivated using a simulation study and a real data example.     

A stochastic model for inter-keypress times in a typing task

A mathematical model for the inter-keypress times (IKT) in a typing task is proposed. The model, which includes a diffusion process terminated by a single response threshold, was evaluated using data obtained from typists. The differences in performance for successive cross-hand and within-hand keypresses were examined using IKT distributions and hazard functions, and it was shown that the empirical hazard functions could be fit by the theoretical hazard function derived from the convolution of normal and inverse Gaussian random variables. Some possible applications of the model for the evaluation of fatigue and strategic effects in typing are suggested.     

A stochastic model for free recall

A statistical model for verbal learning is presented and tested against experimental data. The model describes a Markov process with a realizable absorbing state, allowing complete learning on some finite trial as well as imperfect retention prior to this trial.This work was carried out while the author was at Lincoln Laboratory, Massachusetts Institute of Technology.Operated with support from the U. S. Army, Navy, and Air Force.     

Normative data for eight neuropsychological tests based on a Danish sample

Normative neuropsychological data have been provided using a sample of 101 persons aged 20 to 54 years. Eighty-seven of the subjects were recruited among patients who had undergone minor surgery, and 14 subjects were volunteers from the staff at the hospital laundry. The measures consisted of seven subjects from the WAIS-R, the trail-making test, symbol digit modalities test, auditory-verbal learning test, story recall test, visual gestalt test, recurring figures test, verbal fluency, and Purdue pegboard test. These measures were selected because of suitability in regard to time taken for testing each subject and their sensitivity to subtle changes in neuropsychological functioning. The sample was arbitrarily divided into three age groups, and for each of the three samples, mean, standard deviation, and range were calculated for each test. The results of the Information and Vocabulary subtests from the WAIS-R, education, and social status were applied as independent variables in linear regression analyses where each of the neuropsychological tests, in turn, was the dependent variable. For the oldest age group, age in addition was used as an independent variable. Significant linear relationships, which accounted for an optimal part of the variance, were selected for clinical application.     

A stochastic model for test-retest correlations

A simple stochastic model is formulated in order to determine the optimal time between the first test and the second test when the test-retest method of assessing reliability is used. A forgetting process and a change in true score process are postulated. The optimal time between tests is derived by maximizing the probability that the respondent has not remembered the response on the first test and has not had a change in true score. The resulting test-retest correlation is then found to be a linear function of the true reliability of the test, where the slope of this function is the key probability of not remembering and having no change in true score. Some numerical examples and suggestions for using the results in empirical studies are given. Specific recommendations are presented for improved design and analysis of intentions data.This research was made possible by a grant from the Center for Food Policy Research, Graduate School of Business, Columbia University, New York, New York, 10027.     

Some approximate tests for repeated measurement designs

Four approximate tests are considered for repeated measurement designs in which observations are multivariate normal with arbitrary covariance matrices. In these tests traditional within-subject mean square ratios are compared with critical values derived fromF distributions with adjusted degrees of freedom. Two of them—the approximate and the improved general approximate (IGA) tests—behave adequately in terms of Type I error. Generally, the IGA test functions better than the approximate test, however the latter involves less computations. In regards to power, the IGA test may compete with one multivariate procedure when the assumptions of the latter are tenable.The author wishes to thank Garrett K. Mandeville for his careful reading of the final version of the paper.     

Activity measures in stress-attenuated novelty tests as possible analogues for extraversion in rats: Some experimental results

In an attempt to extend and validate Garcia-Sevilla's (1974) hypothesis proposing ambulation in a non-stressful open field (OF) as an animal analogue of human extraversion, ambulatory behaviour and rearing behaviour were studied and compared in several experiments with genetically-unselected rats. The effects of variation of OF auditory stimulation level, the correlation with a two-way avoidance-learning situation and the effects of a stimulant dose of d-amphetamine and an anxiolytic one of diazepam upon rearing and ambulatory behaviours were studied. All in all, our results support some of the requirements of the hypothesis, but also generate some additional problems. The results show that the number of rearings could be a better and more sensitive measure of variations in the level of arousal and a better predictor of shuttle-avoidance conditioning than ambulation. However, all activity measures are at least moderately intercorrelated, and they become grouped when results are factor analysed. All the results are discussed with reference to Eysenck's personality theory and Gray's anxiety theory, and it is concluded that these measures are too multidetermined and too poorly controlled to represent correctly and in a direct form a personality dimension such as Extraversion. Anyway, this attempt could be a good point of departure for discovering more efficient animal behavioural measures of arousability.     

Some uniqueness results for PARAFAC2

Whereas the unique axes properties of PARAFAC1 have been examined extensively, little is known about uniqueness properties for the PARAFAC2 model for covariance matrices. This paper is concerned with uniqueness in the rank two case of PARAFAC2. For this case, Harshman and Lundy have recently shown, subject to mild assumptions, that PARAFAC2 is unique when five (covariance) matrices are analyzed. In the present paper, this result is sharpened. PARAFAC2 is shown to be usually unique with four matrices. With three matrices it is not unique unless a certain additional assumption is introduced. If, for instance, the diagonal matrices of weights are constrained to be non-negative, three matrices are enough to have uniqueness in the rank two case of PARAFAC2. The authors are obliged to Richard Harshman for stimulating this research, and to the Associate Editor and reviewers for suggesting major improvements in the presentation.     

A stochastic model for rote serial learning

A model for the acquisition of responses in an anticipatory rote serial learning situation is presented. The model is developed in detail for the case of a long intertrial interval and employed to fit data where the list length is varied from 8 to 18 words. Application of the model to the case of a short intertrial interval is considered; some predictions are derived and checked against experimental data.The author wishes to thank Professors C. J. Burke and W. K. Estes for advice and assistance in carrying out this research.