Temporal control by signals of interval duration within variable-interval schedules

Rats' lever pressing produced sucrose reinforcers on a variable-interval schedule where, in different conditions, the duration of a stimulus presented immediately after reinforcement was either correlated or uncorrelated with the duration of the current interreinforcement interval. Under the baseline schedule, in which no stimulus was presented, the minimum interreinforcement interval was 8 s and the mean postreinforcement pause of each subject approximated this value. Response rates increased slowly over the first 10 to 15 s and then remained roughly constant throughout the remainder of the interval. In both the correlated and uncorrelated conditions, the added stimulus resulted in the postreinforcement pauses lengthening to values in excess of the duration of the preceding stimulus. This resulted in a poststimulus pause which was, in most cases, roughly constant irrespective of the duration of the preceding stimulus, or of the reinforcement contingencies prevailing immediately after stimulus offset. Local response-rate patterns in the uncorrelated conditions were similar to those obtained under the baseline schedule in which no stimulus was presented. However, in the correlated condition local response rates increased across the remainder of the interreinforcer interval. Further, the rate of acceleration was inversely related to the duration of the preceding stimulus. These results show that a correlation between stimulus duration and the ensuing time to reinforcement can control behavior—a type of temporal control not previously reported.     

Intelligence and age as predictors of motor performance

The Yule-Oseretsky test of motor performance was administered to 10 ‘undifferentiated’ mentally-retarded adults, 10 normal children and 10 normal adults. In accordance with Denny's (1964) 3-group design, the children were matched on mental age with the retardates, the normal adults were matched on chronological age with the retardates, and the children and normal adults were matched on intelligence quotient. The results showed that mental age predicted performance on both fine and gross motor tasks, with the children and retarded adults both obtaining similar relatively-low scores.     

Acquisition and retention of gestures by apraxic patients

The purpose of this study was to examine whether apraxic-aphasic patients with parietal lesions had difficulty learning lists of gestures and whether the performance deficits they displayed resulted from an inability either to consolidate this information in memory or to retrieve the information once stored. The findings indicate that apraxic-aphasic patients do have difficulty acquiring lists of gestures. This inability to reproduce gestural information was not associated with a retrieval disorder, but instead the apraxic-aphasic subjects could not consolidate the information in memory.     

Visual and verbal codes: Spatial information survives the icon

Three experiments are reported to demonstrate partial independence of identity and spatial position information concerning visually presented symbols. Experiment I shows that performance on these forms of information improves at different rates as a function of exposure duration. Experiment II shows that performance on one can be traded against the other. Experiment III demonstrates partial statistical independence of item and position responses and shows that increases in the duration and delay of the probe facilitate performance. Some implications of these experiments for theories involving mandatory verbal encoding of visual symbol-arrays are discussed. A model is proposed comprising visual and name stores with different acquisition rates and capacities. Both are indexed by identity but the visual code can also be interrogated by spatial cues.     

The concurrent validity of three self-report measures of borderline personality

The recent accumulation of self-report measures of borderline personality disorder (BPD) affords the opportunity to evaluate both the construct validity of the concept and the quality of these measures. This study examines the relationship among three recently developed self-report instruments for assessing BPD from the Personality Assessment Inventory (PAI; Morey, 1991), the MMPI Personality Disorders Scales (MPD; Morey, Waugh, & Blashfield, 1985), and the Bell Object Relations Inventory (BORI: Bell, Billington, & Becker, 1986). Data on the three measures were provided by 119 undergraduate subjects from a southeastern university. A correlational analysis addresses the convergence of these measures of BPD, their divergence from measures of different but related traits, and their independence from variance due to method. Application of the Campbell-Fiske (1959) criteria indicates adequate convergence for all the BPD measures but a lack of discriminant validity for the BORI scales. The fit of the data to a structural model of construct validity is tested using confirmatory factor analysis, and these results are consistent with the hypothesis of a latent borderline trait factor independent of measurement method factors. In sum, the construct validity of the borderline personality concept using self-report methodologies receives support, and a strong association between borderline personality and paranoid phenomena is also suggested.     

Why believe what people say?

The basic alternatives seem to be either a Humean reductionist view that any particular assertion needs backing with inductive evidence for its reliability before it can retionally be believed, or a Reidian criterial view that testimony is intrinscially, though defeasibly, credible, in the absence of evidence against its reliability.Some recent arguments from the constraints on interpreting any linguistic performances as assertions with propositional content have some force against the reductionist view. We thus have reason to accept the criterial view, at least as applied to eyewitness reports. But these considerations do not establish that any rational enquirer must have the concept of other minds or testimony. The logical possibility of the lone enquirer, who uses symbols and thereby expresses some knowledge of his world, remains open — but it is a question we have no need to pronounce upon.The practice of accepting observation-statements is in fact extended to chains of testimonies believed to start in perception or in some other kind of justification, but the arguments for doing this are not so clear.I am indebted for helpful discussions of earlier versions of this paper to audiences at Macquarie University (where I was kindly given research facilities), at the conference of the Australasian Association for Philosophy in Sydney in 1990, at St. Andrews, and also to a referee for this journal.