Binocular cues in the perception of distance of a point source of light

The ability to make egocentric distance estimates of a single point source of light, seen in darkness and without the cues of changing size and luminance, was investigated in sixteen observers. The attenuation required to maintain constant luminance, when the target was viewed from different distances, was shown to follow the inverse square law providing the angle subtended by the light was less than 20 s arc. Distance changes were also simulated by means of a split mirror which produced vergence cues, or by test lenses to provide accommodation cues. Over the range 0.5 to 9.2 m distance estimates were surprisingly accurate, although there was some overestimation of near and underestimation of far distances. Most observers made good judgements when only convergence cues were varied, whereas no observers made consistently good judgements when only accommodation cues were varied. The difficulties are discussed in terms of the accommodation-convergence link. When distance was simulated by changing convergence and accommodation cues, estimates were not as good as when real distance was changed. Since good estimates were made with brief target exposures, these judgements were not based on subsequent convergence or accommodation changes. It is suggested that the metric or reference against which the apparently absolute judgements were made was the efferent demand signal associated with a 'resting' position of convergence in darkness.     

Predicting diagnosis performance with measures of cognitive style

This study examines the relationship between performance on a context-independent fault diagnosis task and two dimensions of cognitive style: field dependence/independence (D-I) and focusing/scanning (F-S). The effects on diagnosis performance of training and the ability of both dimensions of style jointly to predict fault-finding ability were considered. The results showed that field independents and focusers were superior fault diagnosticians. Training, in the form of verbal feedback messages, was uniformly effective for the D-I dimension although field independents maintained a superior level of performance, over field dependents. In general, for the F-S dimension, training had little effect on either the focusers or scanners. A combination of scores on the F-S and D-I dimensions significantly enhanced the proportion of the variance in testing efficiency that could be accounted for during fault-finding. Finally it is argued that the F-S and D-I dimensions should be recognized as measures of ability, not style. Future research should be directed at identifying between subject differences on fault diagnosis tasks with reference to theories of information processing.     

On estimating processing variance: commentary and reanalysis of Kail's "Developmental functions for speeds of cognitive processes".

A recent paper by Kail (1988) in this journal appears to contain a significant error in the data analysis. The "goodness-of-fit" coefficients reported which suggest that overall about 94% of the variance can be accounted for by the model seem to be a substantial overestimation as a result of inappropriate procedures for statistical modeling. Using the data made available to us by Kail, we have reanalyzed these results. The corrected values range from 0.9 to 92.1% for the individual tasks with an overall average between 40 and 60%. We suggest that the support for the original conclusions is considerably weaker than reported.     

Cardiovascular reactivity and interpersonal influence: active coping in a social context

Previous studies have demonstrated that effortful attempts to secure positive outcomes or avoid negative outcomes produce significant increases in systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR). Although these effects of active coping on cardiovascular reactivity are central in current psychosomatic theories, virtually all of the research to date has used impersonal, asocial tasks. Our two studies examined the cardiovascular effects of effortful attempts to influence other people. In Study 1, male subjects attempting to influence the opinions of their discussion partner to improve their own chances of winning money displayed significantly greater SBP, DBP, and HR reactivity. In Study 2, we obtained similar effects on SBP and DBP reactivity in men and women, while both preparing an influence attempt and making that attempt. Furthermore, reactivity levels were larger as the magnitude of incentive for successful persuasion increased. Implications of this interpersonal equivalent of active coping for the development of cardiovascular disease are discussed.     

Predicting Contraceptive Efficacy: A Discriminant Analysis of Three Groups of Adolescent Women1

The relationship of knowledge and attitudes to adolescent contraceptive efficacy was investigated in a multivariate study, with demographic and sexual history variables covaried. Subjects were unmarried, sexually active 15- to 19-year-old women. Two studies were conducted: one using a large and representative sample and the second using a smaller, high socioeconomic status sample that is more typical of samples generally used in earlier research. Subjects were classified as effective, ineffective, or nonusers of contraception, based on both frequency of use and effectiveness of the method(s) they used. Two discriminant function analyses were performed to determine (a) whether knowledge and attitudes contributed to discrimination among the groups over and above discrimination attributable to demographic and sexual history variables, and (b) which variables distinguished ineffective users from both other groups. The results of both studies indicate that attitudes, particularly attitudes toward contraception, are strong predictors of patterns of contraceptive use. Ineffective users were distinguished from nonusers by their greater knowledge of contraception, and from both other groups by their greater sexual activity and more positive attitudes toward intercourse. The discussion focuses on the theoretical implications of the results, the usefulness of the effective/ineffective/nonuser categorization, and applications of these findings to design of interventions.     

Counting On Blood Donors: Increasing the Impact of Reminder Calls

Two experiments were conducted to see if blood drive attendance could be increased by altering the content of reminder calls. In Experiment 1 college students received either a standard reminder (the place, time, and necessity of eating beforehand) or a commitment-enhancing reminder in which they agreed to be "counted on". Those in the latter condition were significantly more likely (p <.007) to attend a blood drive. Experiment 2 demonstrated that an alternate wording for the commitment-enhancing message was possible; that a verbal response was necessary to ensure the commitment; and that a message enhancing altruism was not as effective. The studies suggest that asking for an additional commitment during a reminder call can appreciably increase blood drive participation rates.     

Teaching social skills to emotionally disturbed adolescent inpatients

A social skills training program was evaluated with emotionally disturbed adolescent inpatients. The targeted social skills required an action or reaction within six skill areas. The program was adapted from a commercially available social skills training game that features the use of response specific feedback, self-monitoring, individualized reinforcers, and individualized performance criteria. A peer conducted the baseline and posttraining sessions while the training was conducted by an adult who had no previous interactive history with the subjects. A multiple baseline design across groups demonstrated that the program increased appropriate responding in all skill areas and that these effects generalized during the posttraining peer conducted sessions. A generalization test indicated that the subjects used their newly learned skills with a novel adult outside the training setting. The program appears quite applicable to emotionally disturbed adolescents since it targets skills in a variety of areas and employs standardized procedures to enhance replicability.     

The ABCs of categorical perception

Studies of speech perception first revealed a surprising discontinuity in the way in which stimulus values on a physical continuum are perceived. Data which demonstrate the effect in nonspeech modes have challenged the contention that categorical perception is a hallmark of the speech mode, but the psychophysical models that have been proposed have not resolved the issues raised by empirical findings. This study provides data from judgments of four sensory continua, two visual and two tactual-kinesthetic, which show that the adaptation level for a set of stimuli serves as a category boundary whether stimuli on the continuum differ by linear or logarithmic increments. For all sensory continua studied, discrimination of stimuli belonging to different perceptual categories was more accurate than discrimination of stimuli belonging to the same perceptual category. Moreover, shifts in the adaptation level produced shifts in the location of the category boundary. The concept of Adaptation-level Based Categorization (ABC) provides a unified account of judgmental processes in categorical perception without recourse to post hoc constructs such as implicit anchors or external referents.     

An assessment of decision-making as a possible factor in the age-related loss of contrast sensitivity

The possibility that changes in decision-making may contribute to the age-related decline in contrast sensitivity has been investigated in nineteen young subjects (ages 21-38 years) and twenty-seven old subjects (ages 55-92 years). A signal detection paradigm was employed in which the detection of stationary sinusoidal grating patterns was measured at 3 and 15 cycles deg-1 for a range of contrasts which were psychophysically equivalent for each subject. A decline in contrast sensitivity with age at the spatial frequencies studied was confirmed for contrast thresholds obtained both by the ascending method and from the 50% hit rate for detection of the grating pattern. The criterion adopted for decision-making, expressed as both beta and percentage bias, did not change significantly between young and old subjects at 15 cycles deg-1. At 3 cycles deg-1, criterion beta did not change significantly at X0.8, X1.0, or X1.2 contrast threshold, but at contrast giving 50% hit rate there was a significant increase with age. The percentage bias increased significantly at contrast threshold but not at 50% hit rate. It is inferred from the results that the loss of contrast sensitivity was not accountable in terms of the adoption of a more conservative criterion by older subjects. Hence visual loss in ageing is attributed to changes within the visual pathway rather than within higher decision-making centres.