BAND AID: First steps toward an ICAI system

BANDAID is an intelligent computer-assisted instruction (ICAI) system designed for students learning to program in BASIC. The major thesis is that beginning students need a friendly environment, that is, one in which information about the language and the system are immediately available. The system accepts most commands without switching levels: BASIC lines are parsed on input with very specific error messages. An editor allows corrections of BASIC lines. The program can be traced while running, and an indefinite number of HELP comments can be written for the system. Without leaving the BASIC environment, the user can interact with the CMS monitor of the main machine running the program. Although no English language comments or questions are allowed, the system is modular so that additions of restrictive dialogue interaction and guided tutoring are possible. Illustrations are presented showing the capabilities of the system. The paper also presents some of the implementation details of BANDAID. A flexible system requires implementation in LISP, so examples of how the system programmer interacts with LISP during debugging are given. Although still incomplete, the system runs satisfactorily and can be used easily by beginning students and by psychologists interested in how people learn complex subjects.     

Fundamental frequency as a cue to postvocalic consonantal voicing: Some data from speech perception and production

Several recent studies by Lehiste have reported that changes in fundamental frequency (F0) can serve as a cue to perceived vowel length and, furthermore, that the perceived lengthening of the vowel can influence perception of the voicing feature of stop consonants in syllable-final position. In Experiment 1, we replicated Lehiste’s basic results for stop consonants in final position. Experiment 2 extended these results to postvocalic fricatives. The final consonant in syllables of intermediate vowel duration was more often perceived as voiced when F0 was falling than when F0 was monotone. In Experiment 3, we examined the F0 contours produced by eight talkers before postvocalic stop consonants and fricatives in natural speech for minimal pairs of words differing in voicing. The amount of change of F0 over the vowel was no greater before voiced than voiceless consonants, suggesting that the earlier perceptual effects cannot be explained by appealing to regularities observed in the production of F0 contours in vowels preceding postvocalic consonants.     

Strategies of rule discovery in an inference task

It has long been known that subjects in certain inference tasks will seek evidence which can confirm their present hypotheses, even in situations where disconfirmatory evidence could be more informative. We sought to alter this tendency in a series of experiments which employed a rule discovery task, the 2-4-6 problem first described by Wason. The first experiment instructionally modified subjects confirmatory tendencies. While a disconfirmatory strategy was easily induced, it did not lead to greater efficiency in discovering the rule. The second experiment introduced subjects to the possibility of disconfirmation only after they had developed a strongly held hypothesis through the use of confirmatory evidence. This manipulation also failed to alter the efficiency of rule discovery. In the third experiment, subjects were taught to use multiple hypotheses at each step, in the manner of Platt's “Strong Inference”. This operation actually worsened performance. Finally, in the fourth experiment, the structure of the problem was altered slightly by asking subjects to seek two interrelated rules. A dramatic increase in performance resulted, perhaps because information which in previous tasks was seen as merely erroneous could now be related to an alternative rule. The four studies have broad implications for the psychological study of inference processes in general, and for the study of scientific inference in particular.     

Interaction of genetics and separation in canine hyperkinesis and in differential responses to amphetamine

A model of childhood hyperkinesis, using the Telomian-beagle hybrid dog, is described, demonstrating the interactions of genetics and separation in the development of this syndrome and in the favorable responses of some of these dogs to amphetamine. This work represents the collaboration of three laboratories, utilizing chiefly methods of inhibitory training. Inducing separation distress enhanced the resistance to inhibitory training and the favorable responses to amphetamine.     

Sequential precession and diminishing returns in the acquisition of a motor skill

As students progress to higher and higher levels in the acquisition of a skill their number gets smaller and smaller. This article concerns the average length of time it takes the members of these successively smaller groups to complete earlier stages of skill acquisition. In the data presented, which concern Red Cross swimming, the more advanced a group is the less time its members take on the average to complete a preceding stage (sequential precession). The discussion section brings out a second relation in the same data: Namely, the further the same students advance in skill acquisition the smaller the advantage they enjoy over other students at the same level (diminishing returns).     

Statistical significance tests for binormal ROC curves

Statistical significance tests are derived and evaluated for measuring apparent differences between an obtained and an expected binormal ROC curve, between two independent binormal ROC curves, and among groups of independent binormal ROC curves. A binormal ROC curve is described by two parameters which represent the spread of the means and the ratio of the standard deviations of the two underlying Gaussian decision variable distributions. To test the significance of apparent differences between or among ROC curves, approximate χ² statistics for each of the three tests were constructed from maximum likelihood estimates of the two parameters defining the binormal ROC curve. The performance of each test statistic was evaluated by simulating five-category rating scale data with equal numbers of noise and signal-plus-noise trials (set at 50, 250, and 500) for each of three typical ROC curves. For the significance test involving only one ROC curve, rating scale data were generated from the chance diagonal of the ROC space also. Although test performance was found to be somewhat dependent on the number of trials and on the location of the ROC curve in the ROC space, comparisons of the obtained and expected fractions of (falsely) significant results at various α levels showed the proposed statistical significance tests to be reliable under practical experimental conditions.     

Positive conditioned suppression: Transfer of performance between contingent and noncontingent reinforcement situations

Five homing pigeons were trained on concurrent variable-interval schedules. A fixed-duration stimulus was occasionally presented on one key; and, in various conditions, this stimulus terminated (a) without reinforcement, (b) in noncontingent reinforcement, (c) with reinforcement contingent on a response on the key on which the stimulus was presented, and (d) with reinforcement contingent on a response on the key on which the stimulus was not presented. Initially, a stimulus terminating in noncontingent reinforcement generally produced decreased response rates on both keys during the stimulus. Contingencies, however, reliably produced increased rates during the stimulus on the key on which the contingency was arranged, relative to the rate on the concurrently available key. Contingency conditions were followed by noncontingency conditions in which the separation of rates caused by contingencies was maintained. When rates during the stimulus were compared with response rates on the same keys in the absence of the stimulus, contingency-caused rate increases and decreases were again found, but only the rate decreases were maintained in subsequent noncontingency conditions. Further data suggested that the contingency-caused rate changes were not maintained when the stimulus terminated without reinforcement, and that they were unaffected by a threefold decrease in the reinforcement rate provided by the baseline schedules. The results support the suggestion that performance in the positive conditioned suppression procedure results from concurrent and multiple schedule interactions. They further suggest that the production of either acceleration or suppression is dependent on adventitious and historical contingencies.     

Teacher reactions to school-based consultation services: A multivariate analysis

The impact of consultation services on teachers' preferences for consultation versus referral approaches and upon teachers' perceptions of severity for common acting out, withdrawal, and academic types of student problems were investigated. The subjects were 96 teachers whose public and parochial schools were matched and randomly assigned to treatment and control groups. Following a 14-week period during which advanced school psychology graduate students served as consultants in the treatment schools, the Pupil Problem Behavior Inventory (PPBI) was administered to all teachers. The results of a repeated measures MANOVA analysis indicated that the teachers in the treatment group rated the acting out and academic problems on the PPBI as significantly less severe than did teachers in the control group. The subjects in both the treatment and control groups indicated a significant preference for consultation rather than referral services for all types of student problems presented in the PPBI. There was a moderate, positive correlation between perceived problem severity and teacher preference for referral rather than consultation services. The study's results were interpreted as supportive of the consultation model.