A behavioral frequency discrimination paradigm for use in adult primates

A psychophysical apparatus and procedure that can be used to define the performance and estimate the thresholds of frequency discrimination in adult primates is described. This protocol has been used to train adult owl monkeys to discriminate differences in the frequencies of successively presented sinusoidal tactile stimuli delivered to a restricted skin surface of a single digit, and to train a second set of adult owl monkeys to discriminate. differences in frequencies between paired auditory tonal stimuli. The thresholds estimated with this procedure are comparable to those measured in other primates. The advantages of using this procedure for combined behavioral and physiological studies are discussed.     

Successiveness discrimination: Two models

Two models for successiveness discrimination, an attention-switching model and a duration-discrimination model, are described. Data are reported from a forced-choice successiveness discrimination task in which the standard stimulus assumed one of three values during a session. Of major interest is the ability of the models to account for the absence of observed variation in performance with changes in value of the standard. Conventional signal detection-type models or discrete state models would be unable to account for the data.     

Two strategies in fricative discrimination

Synthetic noises from a [∫]-[s] continuum, followed by vocalic portions that influenced the location of the [∫]-[s] boundary in an identification test, were presented in AXB and fixed-standard AX discrimination tasks. The majority of naive subjects perceived these fricative-vowel syllables fairly categorically in both tasks; that is, discrimination functions followed the patterns predicted from identification scores and showed shifts contingent on the nature of the vocalic portion. However, two subjects achieved much better discrimination scores than the rest, and so did three experienced listeners and a group of less experienced subjects who had received some discrimination training in the AX task. These listeners, who (judging from their higher accuracy, pattern of responses, and subjective reports) successfully followed the nonphonetic strategy of restricting attention to the spectral properties of the fricative noise, were not influenced by different vocalic contexts. These results support the hypothesis that influences of vocalic context on fricative identification are tied to a phonetic mode of perception.     

Two interpretations of the discrimination parameter

In this paper we propose two interpretations for the discrimination parameter in the two-parameter logistic model (2PLM). The interpretations are based on the relation between the 2PLM and two stochastic models. In the first interpretation, the 2PLM is linked to a diffusion model so that the probability of absorption equals the 2PLM. The discrimination parameter is the distance between the two absorbing boundaries and therefore the amount of information that has to be collected before a response to an item can be given. For the second interpretation, the 2PLM is connected to a specific type of race model. In the race model, the discrimination parameter is inversely related to the dependency of the information used in the decision process. Extended versions of both models with person-to-person variability in the difficulty parameter are considered. When fitted to a data set, it is shown that a generalization of the race model that allows for dependency between choices and response times (RTs) is the best-fitting model.     

On the theory of test discrimination

This paper discusses the properties of distributions of test scores and advances the view that the properties of the distribution should depend on the function which the test is intended to perform. A theory of test discrimination is developed which defines discriminatory capacity in terms of the number of relations of difference established by the operation of administering a test ofk items to a sample ofn individuals. A simple proof is presented which indicates that maximum discrimination between individuals is achieved when tests are constructed to yield distributions of the rectangular form. A coefficient of test discrimination is developed. The problem of obtaining in practice distributions approximating to the rectangular form is briefly discussed.This paper was prepared under the auspices of the Defence Research Board, Ottawa, Canada.     

A test of two theories of shape discrimination

An experiment is reported which confirms a prediction from the writer's theory of shape recognition. The same experiment is held to refute an alternative theory, but this refutation is not conclusive, since the alternative theory has not been clearly stated and can be interpreted in several conflicting ways. It is shown that these possible interpretations of the alternative theory all yield predictions which are not confirmed by the present findings.     

Two new test statistics for the rasch model

It is shown that the presently available statistical tests for the Rasch model are insensitive to violation of the unidimensionality axiom. Two new test statistics are presented. The first one,Q ₁, is sensitive to the same effects as the presently available statistics, but has some desirable properties of a nonstatistical nature. The second statistic,Q ₂, is sensitive to violation of local stochastic independence and unidimensionality and thus fills an existing gap.     

Two types of behavioral contrast in discrimination learning

Two groups of pigeons received daily discrimination training at two values on a line-tilt continuum. S+ (VI 1) and S- (EXT) intervals alternated, and a 30-sec criterion of no responding to S- was required before S+ returned. Rates of responding to S+ showed two separate contrast effects: at an intermediate stage of training a high peak rate appeared which declined, later in training, to a stable level still in excess of the VI baseline rate. The peak rate was correlated with the total number of responses to S-, while the final rate was not; suggesting that the peak rate and final rate may not be functions of the same variable. These results were compared with performance on a red-green discrimination where the two stages were not so clear. A line-tilt discrimination was repeated with fixed length S- intervals terminated by TO, and showed the same contrast magnitude in the final rate without any peak. The peak rate was interpreted as an effect of the ;punishment' contingency where responding to S- prolongs S- for 30 sec, while the final rate was taken to be analogous to previous demonstrations of contrast.     

Behavioral engineering: two apparatuses for toilet training retarded children

Daytime incontinence is a major problem for retarded children. A training procedure for eliminating this problem should be facilitated by an apparatus that provided the trainer with an immediate signal when the child voided so that the trainer could react immediately. Two apparatuses were developed for this purpose: a toilet-chair apparatus to signal proper toileting and a portable pants-alarm apparatus to signal wetting of the pants. A reprimand was given when pants wetting occurred whereas positive reinforcement was given for proper toileting. Results with four profoundly retarded children indicated the reliability of the apparatuses in practice and the effectiveness of a toilet training program that used the two apparatuses.     

The effects of intradimensional and extradimensional shifts on visual discrimination learning in humans and non-human primates

Human subjects and non-human primates (the common marmoset) were trained on a series of reversals of both a simple (stimuli varying along one dimension) and compound (stimuli varying along two different dimensions) visual discrimination, using computer-generated stimuli. They were then shifted to a third series of reversals using completely novel compound stimuli. Those humans and marmosets for which the previously relevant dimension remained relevant, following the shift (shapes to shapes or lines to lines; intradimensional shift) made fewer errors than those for which the previously irrelevant dimension became relevant (shapes to lines or lines to shapes; extradimensional shift). These findings suggest that both humans and marmosets can learn to attend to the specific attributes or dimensions of a stimulus and use this information in visual discrimination learning.     

A test of the discrimination account in equivalence class formation

An equivalence class is typically established when a subject is taught a set of interrelated conditional discriminations with physically unrelated stimuli and additional, untaught, conditional discriminations are then demonstrated. Interestingly, and perhaps counter-intuitively, the relations among the stimuli within such a class are not necessarily equal. Rather, some members of the class are differentially related to other class members. There are two opposing theories of why relations among stimuli are unequal: nodal and discrimination accounts. The former suggests that delayed emergence is due to nodal distance (i.e. the number of intervening stimuli) while the latter suggests that delayed emergence is an artifact of the training procedure itself. The current paper reports on the first empirical study that directly compares these theories. Forty participants were given training designed to establish two 5-member equivalence classes. Participants’ response speed supported the nodal account, thus suggesting that unequal relations among equivalence class members is not an artifact of the training procedure.     

Wepman test of auditory discrimination: What does it discriminate

This study investigated auditory discrimination as a function of ethnic group membership within the same socioeconomic status (SES). Subjects were 126 randomly selected six-year-old students attending schools in the lower SES community of southeast San Diego. Only students with no known speech or hearing defects and of normal intelligence were included. They were assigned to one of three categories: Black, Chicano, or Anglo.Subjects were administered four tests in a counterbalanced design: the Wepman, the Gross, and the Ott. The latter two were developed for use with Black dialect and Spanish-speaking youngsters, respectively. The ANOVA results indicated a reliable difference between the main effects of the groups (F=40.34,p<.001) and tests (F=72.82, p<.001), with a significant interaction between tests and groups (F=44.91, p<.001). Interaction effects were evaluated with the Dunn theorem. Significant differences were found among Anglo, Black, and Chicano students on the discrimination list for Spanish sounds (Ott) and a significant Anglo/Black difference on the discrimination test for Black dialect (Gross). Contrary to previous findings, there were no differences between the groups on the Wepman Test of Auditory Discrimination (WTAD). However, there are significant differences between groups on separate items of this test.     

Inexpensive apparatuses for use with young children: A WGTA variant

This report details steps for constructing devices adapted from the WGTA and for use with young children in discrimination tasks. The devices are specially made Jack-in-the-boxes to which various discrimination forms can be attached. The units are both durable and reliable and meet the criteria of ease of construction, low cost, ease of operation, and strong reinforcing qualities. The units have been successfully used with normal and retarded children and with children with motor difficulties and/or muscle weaknesses from 15 to 60 months of age.     

Two short-term,cognitive interventions for the reduction of test anxiety

Abstract

Relative efficacy of Attentional Skills Training and Systematic Rational Restructuring as short-term (50 minutes each), cognitive interventions was determined on a sample of ninth-grade girls from India. Only Attentional Skills Training and not Systematic Rational Restructuring has been found to be effective for high test-anxious girls (regardless of intelligence), not only in the reduction of state test anxiety and its worry state component, but also in the reduction of anxiety interference and in the improvement of the estimated percent time spent on task. However, neither of the interventions improved the performance on the two difficult experimental tasks when compared to controls.