Binocular brightness combinations: Additive and nonadditive aspects

A conjoint measurement procedure is used for the measurement of binocular brightness as a function of left and right luminance inputs. For nonzero stimulation, the data confirm earlier findings: the system can be described as additive with a scale exponent of 1. If zero stimulation is included, however, no additive solution can be found (due to Fechner’s paradox). This fact, combined with various critical remarks in the literature with respect to the existence of a real luminance-averaging system, has led us to propose a model which takes account of Fechner’s paradox, and incorporates “realistic” exponents without requiring a multistage processing mechanism where different levels are characterized by different sensory scales. The proposed model makes the weighting coefficients for the two eyes dependent in a continuous way on the strength of stimulation in the two eyes, especially on the amount of contrast of the monocular stimuli. For zero background stimulation, contrast can be expressed in terms of luminance of the stimulus. In this way, the model is reduced to a simple testable form. While it much simpler than Engel’s (1969) model, the experimental results indicate that it might also work for the more general case.     

A COMPARISON OF NORTH-AMERICAN AND BRAZILIAN COLLEGE STUDENTs' PERSONALITY PROFILES ON THE 16 PF QUESTIONNAIRE

Le questionnaire de personnalité 16 PF (Forme A) a été traduit en portugais et soumis à un échantillon représentatif des étudiants de Sao Paulo (Brésil), comprenant 770 H et 555 F. Pour chaque facteur, les résultats ont été comparés à ceux d'un échantillon standardisé d'étudiants américains: les étudiants brésiliens sont, en général, moins sociables (A —) et moins enthousiastes (F —), plus soupçonneux (L +) et plus imaginatifs (M +); ils sont également moins conservateurs (Qi +) et plus indépendants (Q2 +). l'analyse de second ordre fait apparaître les Brésiliens comme plus anxieux et plus introvertis, montrant également plus de spontanéité et de créativité que les sujets américains. On constate enfin l'existence de différences entre hommes et femmes, tant à l'intérieur de chaque groupe qu'entre les deux échantillons.     

Effects of grouping on the pupillary response in a short-term memory task

Subjects heard strings of nine digits for immediate recall, either at a monotone 1/sec. rate or in groups of three digits separated by pauses. Concurrent measurements of pupil size show a steady dilation in the monotone condition, and brief dilation-constriction waves during the pauses of grouped presentation. The results are consistent with hypotheses concerning rehearsal in the two modes of presentation. Pupillary dilations apparently accompany episodes of covert rehearsal.     

A Survey of Undergraduate Women's Social Regulations

Data concerning women undergraduates' social regulations in a selected number of coeducational colleges and universities were collected in order to identify liberal regulations in use or under consideration in these institutions grouped according to size, control, and regional location. The collected information supported considerable liberalization in the areas of room and apartment visiting, off-campus living, clothing, sign-out, curfew hours, and coeducational residence halls. Larger respondent institutions' regulations and those of Western institutions evidenced the most liberalization, while regulations of public-control and private-control institutions were considered equally liberal.     

USING INTERMITTENT REINFORCEMENT TO PROGRAM MAINTENANCE OF VERBAL/NONVERBAL CORRESPONDENCE

We investigated the effects of an intermittent reinforcement procedure on maintenance of verbal/nonverbal correspondence with nutritious snack choices in a day-care setting. Nutritious snack choices were first established using correspondence training procedures in a multiple baseline across three children. Withdrawal of the procedures with one subject led to loss of appropriate responding, suggesting the need for a maintenance strategy. The intermittent reinforcement procedure was implemented in a multiple baseline across subjects. Nutritious snack choices were observed consistently during the intermittent reinforcement condition and the subsequent extinction condition.     

Effects of visual-field and matching instruction on event-related potentials and reaction time

Vertical letter pairs were presented randomly in the left and right visual hemifields in a physical identity match and name identity match condition. The reaction times showed a right visual field superiority for name matches, and a left visual field superiority for physical matches. Event-related potentials to letter pairs showed a sequence of three waves: a negative wave (N2, around 270 msec), a positive wave (P3, around 500 msec), and a broad positive slow wave (SW, around 600-700 msec), respectively. P3 and SW amplitudes were consistently larger at the left hemisphere than at the right hemisphere, regardless of the field of stimulation. At both hemispheres, N2 waves were always larger to stimuli presented in the visual field contralateral to a hemisphere than stimuli presented in the visual field ipsilateral to a hemisphere. The positive waves (P3, SW) showed the opposite pattern: smaller amplitudes to stimuli that were presented contralaterally than stimuli that were presented ipsilaterally to a given hemisphere. These results were attributed to a shift in sustained negativity on the directly stimulated hemisphere, relative to the indirectly stimulated hemisphere, reflecting either sensory at attentional processes in the posterior cerebral hemispheres.     

Characteristics of Suicidality Among Adolescents

The identification of high-risk adolescent suicide attempters in a population of depressed and suicidal adolescents is of crucial importance. This retrospective study examined characteristics of suicidality (recent and lifetime, active and passive) and psychopathology (depression, aggression, impulsivity, stressful life events, SCL-90 dimensions) among four groups of depressed adolescent outpatients: (1) suicide attempters who required medical treatment (n = 84), (2) suicide attempters who did not require medical treatment (n = 57), (3) suicidal ideators who had never made a suicide attempt (n = 40), and (4) nonsuicidal patients (n = 44). Results indicate that the nonsuicidal group could be differentiated from the three suicidal groups on the basis of suicidality and psychopathology, and that the three suicidal groups could be differentiated from one another on the basis of suicidality but not psychopathology. These findings are discussed in terms of the usefulness of certain self-report measures of suicidality for identifying suicidal adolescents and for differentiating among them. Furthermore, the findings suggest that psychopathological factors do not determine which suicidal adolescents make a medically dangerous suicide attempt and which do not.