Within-session Changes In Responding During Concurrent Variable-interval Schedules

Five rats and 4 pigeons responded for food delivered by several concurrent variable-interval schedules. The sum of the rates of reinforcement programmed for the two components varied from 15 to 480 reinforcers per hour in different conditions. Rates of responding usually changed within the experimental session in a similar manner for the two components of each concurrent schedule. The within-session changes were similar to previously reported changes during simple schedules that provided rates of reinforcement equal to the sum of all reinforcers obtained from the concurrent schedules. The number of changeovers also changed within sessions in a manner similar to the changes in instrumental responding. These results suggest that changeovers are governed by the same variables that govern instrumental responding. They also suggest that the within-session change in responding during each component of a concurrent schedule is determined by approximately the sum of the reinforcers obtained from both components when both components provide the same type of reinforcer.     

EFFECTS OF EXPLICIT TIMING ON MATHEMATICS PROBLEM COMPLETION RATES IN AFRICAN-AMERICAN THIRD-GRADE ELEMENTARY STUDENTS

A multiple baseline design was used to evaluate the effects of Van Houten and Thompson's (1976) explicit timing procedure on problem completion rates and accuracy levels in African-American third-grade students. During the explicit timing phase, students were told that they were being timed and were instructed to circle the last problem completed at each 1-min interval. Results showed that the explicit timing procedure increased problem completion rates. A decreasing trend in percentage of problems correct also occurred. Exploratory data analysis suggested that decreases in accuracy were not caused by the explicit timing procedure and did not occur in students who had attained high levels of preintervention accuracy. Discussion focuses on recommendations for educators who wish to use timing procedures to increase students' rates of accurate responding.     

Competing interests: The need to control conflict of interests in biomedical research

Individual and institutional conflict of interests in biomedical research have becomes matters of increasing concern in recent years. In the United States, the growth in relationships — sponsored research agreements, consultancies, memberships on boards, licensing agreements, and equity ownership — between for-profit corporations and research universities and their scientists has made the problem of conflicts, particularly financial conflicts, more acute. Conflicts can interfere with or compromise important principles and obligations of researchers and their institutions, e.g., adherence to accepted research norms, duty of care to patients, and open exchange of information. Disclosure is a key component of a successful conflict policy. Commitments which conflict with a faculty member's primary obligations to teaching, research, administrative responsibilities, or patient care also need attention. Institutional conflict of interests present different problems, some of which are discussed in an analysis of an actual problem posed by two proposed clinical trials. This paper is adapted from a lecture presented to a Symposium on Scientific Integrity, Warsaw, Poland, 23 November 1995. Daniel Steiner was Vice-President and General Counsel of Harvard University (1972–92) and in that capacity became familiar with conflict of interest issues. He is currently Counsel to the Boston law firm. Ropes and Gray, and is Adjunct Lecturer in Public Policy at the John F. Kennedy School of Government. Harvard University.     

A new measure for determining children's subjective organization of speech

A new technique for determining children's subjective organization of speech is described. The technique consists of teaching a child a sentence and then repeatedly (1) reading the sentence up to a selected point, (2) sounding a tone, and (3) having the child supply the next word. The time from the tone to the onset of the child's voice is the dependent variable. In the first study 6- and 8-year-old children memorized the following sentence: “John likes to feed the little puppies in the barn.” Their response times suggested that the dominant segmentation pattern consisted of four phrases: a subject phrase, a verb phrase, an object phrase and a modifier phrase. Within each phrase differences between reaction times were on the order of 30 msec. Across phrases they were on the order of 120 msec. The same trend emerged for subsamples of the children with various short-term memory sizes, and for adults. It also appeared for subsamples of the total scores (e.g., first six trials and last six trials). In order to provide further evidence of the technique's validity, different sentences of the same general type were presented to children with short-term memory spans of either 3, 4, or 5. As predicted, it was found that when children's spans corresponded to the number of hypothesized chunks (i.e., 4), they could repeat the sentences verbatim on the first exposure. They could not do so, however, when their spans were lower than that value or when the number of phrases was increased. It was concluded that the new technique is a promising one for assessing young children's patterns of speech segmentation.     

Effects of neutral and positive stimuli on stuttering: “Calling attention to stuttering” revisited

This study investigated the effects of presumably positive and neutral response-contingent stimuli on the occurence of stuttering. Eight adult stutterers spoke spontaneously during a 60-min experimental session, which was divided into three 20-min periods. During Condition I no stimuli were delivered. During Condition II a digital counter and a pair of yellow lights were activated each time the subject stuttered. During Condition III these same response-contingent stimuli were delivered, but with the additional factor that the subject would earn 5¢ each time the counter moved forward and the lights were illuminated. Conditions II and III were counterbalanced across subjects. The experimenter was unaware of which of the two contingencies were operative during Conditions II and III. Results showed no significant changes in occurence of stuttering due to either response-contingent stimulus. A discussion of theoretical and experimental implications is given.     

The use of averaged electroencephalic response techniques in the study of auditory processing related to speech and language

This paper reviews a number of studies done by the authors and others, who have utilized various averaged electroencephalic response (AER) techniques to study speech and language processing. Pertinent studies are described in detail. A relatively new AER technique, auditory brainstem responses (ABR), is described and its usefulness in studying auditory processing activity related to speech and language is outlined. In addition, a series of ABR studies, that have demonstrated significant male—female differences in ABR auditory processing abilities, is presented and the relevance of these data to already established differences in male—female language, hearing, and cognitive abilities is discussed.     

Are there constraints on childhood disfluency?

Analysis of the spontaneous speech of eight stuttering and eight normally fluent children reveals that (a) the location of both stuttering and normal disfluent moments is constrained by sentential constituent structure, and (b) stuttering children experience fluency breakdown with a particular type of constituent (verb phrase) not usually disfluently produced by normals. A view of early stuttering as a sentence planning and integration disorder is present.     

Stuttering and fluency: Exclusive events or points on a continuum?

In recent years, several studies have been conducted in which the fluency of stutterers was compared with that of normal speakers. These investigations have been of two basic types, some involving objective measures of physiologic, aerodynamic, or acoustic features of the subjects' fluent speech signal, and others involving experiments performed in which listeners attempted to distinguish the fluency produced by stutterers from that generated by normal speakers. The body of literature pertaining to each of these two types of investigations is reviewed and interpreted. The interpretations offered are then developed in an effort to shed further light on both fluency and stuttering. Implications for further research, as well as for the evaluation, treatment, and post-therapy assessment of stutterers are drawn.     

Concurrent validity of the WISC-R factor scores

This study investigated the efficacy of predicting academic achievement as measured by the Wide Range Achievement Test using the factor scores of the Wechsler Intelligence Scale for Children-Revised as potential predictors. Both instruments were administered to 200 school children referred for psychological evaluations. Factor scores for the WISC-R were computed according to equations provided by Gutkin (1978). These factor scores then were regressed in a stepwise manner on the Reading, Spelling, and Arithmetic standard scores from the Wide Range Achievement Test. Stepwise regressions also were performed using the traditional Verbal and Performance IQs as the potential predictors. A comparison was made between the results obtained by use of the factors or the more common scores. The results indicated that the Freedom From Distractibility factor score significantly aided in the prediction of Reading and Spelling achievement and was of primary importance in predicting Arithmetic achievement. When the stepwise results using the different scores were contrasted, the factor scores accounted for appreaciably more variance in Arithmetic than did the traditional Verbal and Performance IQs. Derived regression equations are reported along with a discussion of the interpretability of the Freedom From Distractibility factor.