Can skilled performers readily change technique? An example, conventional to wave action breaststroke

There has been a paucity of research that has investigated whether skilled performers of a complex sports skill can readily change their technique. This study was designed to investigate whether swimmers skilled in the conventional breaststroke technique could adjust readily to the wave action technique. Nine masters swimmers with well established and stable movement patterns for the conventional technique were coached in the wave action breaststroke technique. The swimmers were videotaped from the side during maximum speed trials of the conventional breaststroke technique before coaching and the wave action technique after ten 45-minute coaching sessions. The amplitude and phase of the waveforms comprising the vertical displacements of the body parts were determined by Fourier analysis. In response to the coaching, the amplitude of the fundamental frequency of the vertex of the head, shoulders, hips, and knees increased significantly (p < 0.01). The percentage of power contained in the fundamental frequency of the shoulder and hip vertical displacements also increased significantly (p < 0.01). All subjects changed the relative phase of the fundamental frequencies of the vertex, shoulder, and hip vertical displacements. It was concluded that in this complex skill, major changes to the low frequency waveforms comprising the motion were achieved readily.     

Use of a computer-controlled firearms training simulator in perception response time experiments

This paper describes the use of a custom-configured computer-controlled firearms training simulator to measure perception response (reaction) time (RT) to a stimulus in which the degree of threat presented is a manipulable variable across trials. The computer records the number of frames of videotape traversed between the point of presentation of the threat in the video stimulus and the point at which the subject responds by drawing the firearm. For the purposes of data analysis, these frame-count measures are converted to RT measurements. Example data are presented that capture perception RT at both thedraw-stimulus and thefire-stimulus points in situations for which either only one threat or more than one threat exists. Other elements, such as degree of threat and accuracy of response, provide additional data.     

Television distraction and the performance of introverts and extroverts

An experiment was run to test the effect on reading comprehension of distraction by a television programme, which was presented while reading took place. Respondents, classified in terms of extroversion or introversion, carried out two reading comprehension tests in silence and in the presence of a television drama programme. As predicted, extroverts and introverts both performed better in silence, but there was a significant interaction that showed that extroverts performed better than introverts in the presence of television distraction. The findings are discussed in relation to previous research on this subject.     

Discrimination of auditory temporal patterns

Two same-different discrimination experiments were performed for click patterns having a total duration of about 4 sec and interclick intervals ofn × 250 msec, withn a random integer. In Experiment 1, the influence of the physical click group structure on discrimination performance was investigated. In Experiment 2, the effect of the strength of an induced internal clock on discrimination performance was measured. Performance was poor if the group structure of clicks was maintained during a change in click pattern and also if the induced infernal clack strength was low. The performance of about 70% of the subjects improved significantly if either a change in click grouping structure occurred or a strong internal clock could be induced. These results cannot be accounted for with simple models based an single-interval duration discrimination or between-pattern correlation statistics.     

Relevant implication and the case for a weaker logic

We collect together some misgivings about the logic R of relevant inplication, and then give support to a weak entailment logic DJ^d. The misgivings centre on some recent negative results concerning R, the conceptual vacuousness of relevant implication, and the treatment of classical logic. We then rectify this situation by introducing an entailment logic based on meaning containment, rather than meaning connection, which has a better relationship with classical logic. Soundness and completeness results are proved for DJ^d with respect to a content semantics, which embraces the concept of meaning containment.Dedicated to Robert K. Meyer on the occasion of his 60th birthdayThis paper was presented to the Australasian Association for Logic Conference, A.N.U., Canberra, in July, 1992. This Conference commemorated the 60th birthday of Robert K. Meyer, in recognition of the enormous contribution he has made to Logic, especially to Relevant Logic, and of the general lift he has given to the field in his adopted country, Australia. This paper owes its inspiration to Robert Meyer's Farewell to Entailment [37] and his earlier Why I am not a Relevantist [35]. This paper also owes a great deal to Richard Sylvan who has consistently supported weaker relevant logics at a time when stronger relevant logics were in vogue (see especially [47], Chapter 3). In writing this paper, I have also benefited from conversations with Nuel Belnap, Michael Dunn, Kit Fine and Alasdair Urquhart during a period of study leave in 1991. I also thank Robert Meyer, Michael Dunn, Martin Bunder and John Slaney for useful comments on my conference paper. I would also like to thank the referees of this Journal for their helpful comments, which led me to make substantial improvements to this paper.     

Prevalence of ADHD and comorbid disorders among elementary school children screened for disruptive behavior

In the context of a school-based prevention of conduct disorder program, 7,231 first- through fourth-grade children were screened for cross-setting disruptive behavior. Frequencies of DSM-III-R psychiatric disorders and patterns of comorbidity were assessed. We also examined the association of psychiatric diagnosis with child and parent characteristics to determine differential risk based on diagnostic subgroups. Attention deficit hyperactivity disorder (ADHD) and oppositional-defiant disorder (ODD) were the most frequent diagnoses. Mood and anxiety disorders were infrequent as single diagnoses. Patterns of comorbidity demonstrated that both externalizing and internalizing disorders commonly cooccurred with ADHD. More severe degrees of psychopathology and psychosocial risk accrued to the subgroup of youths with ADHD plus a comorbid externalizing disorder.This study was supported by grant MN-46584 from the National Institute of Mental Health.     

Active and passive avoidance following the administration of systemic DSP4, xylamine, or p-chloroamphetamine

Groups of rats were administered either DSP4 (50 mg/kg, ip), xylamine (50 mg/kg, ip), or p-chloroamphetamine (2 X 10 mg/kg, ip), either 2 weeks or 1 week before the testing of two-way active avoidance. DSP4 and xylamine, the selective noradrenaline (NA) neurotoxins, caused a two-way avoidance impairment but p-chloroamphetamine, the selective 5-hydroxytryptamine (5-HT) neurotoxin, did not do so. Pretreatment with desipramine (20 mg/kg, ip) blocked the avoidance impairment caused by DSP4 and xylamine treatment. Neither DSP4 nor xylamine caused any alteration of passive avoidance retention. The biochemical analyses indicated severe NA, but not 5-HT, depletions in the DSP4 and xylamine conditions and drastic 5-HT, but not NA, depletions in the p-chloroamphetamine conditions. These results confirm and extend earlier findings concerning the role of NA in avoidance behavior.     

Saccade latency and warning signals: Effects of auditory and visual stimulus onset and offset

Previous studies have found that a nonspecific visual event occurring at the fovea 50–150 msec after the onset of a peripheral target delayed the initiation of the saccade to that target. The present studies replicated and extended this finding by studying the effects of both visual and auditory warning signals, by examining the effects of onset and offset warning on manual response latency, and by investigating the effects of presenting the warning events in the periphery of the visual field. The results indicated that the interfering effects occur with visual but not auditory stimuli, with saccades but not motor responses, and when the visual warning event occurs either foveally or in the subject’s periphery. Implications for the processes involved are discussed.