Magnitude of luminance modulation specifies amplitude of perceived movement

A compelling impression of movement, which is perceptually indistinguishable from a real displacement, can be elicited by patterns containing no spatially displaced elements. An apparent oscillation, w-movement, was generated by a stationary pattern containing a large number of horizontal pairs of spatially adjacent dots modulated in brightness. The observer’s task was to adjust the perceived amplitude of the w-motion to match the amplitude of a real oscillation. All of the data can be accounted for by a simple rule: If the relative change in the luminance,W = αL/L, between two adjacent stationary dots is kept constant, the distance over which these dots appeared to travel in space comprises a fixed fraction of the total distance by which they are separated. The apparent amplitude of the w-motion increases strictly in proportion with luminance contrast, provided that the contrast is represented in the motion-encoding system by a rapidly saturating compressive Weibull transformation. These findings can be explained in terms of bilocal motion encoders comparing two luminance modulations occurring at two different locations.     

Contextual effects in difference judgments

Manipulating stimulus spacing, stimulus frequency, or stimulus range usually affects intensity judgments. In six experiments, I investigated the locus of analogues of these contextual effects in a “difference” estimation task. When all stimuli elicited the same taste quality, stimulus distribution affected the scale values only when water was included in the stimulus set (Experiments 1–3). When the subjective ranges of two taste qualities were manipulated, different scale values were obtained for the separate qualities in the two conditions (Experiment 4). Manipulation of the expected response distribution did not affect the scale values or the responses (Experiments 5–6). It is concluded that shifts in stimulus distributions or stimulus ranges result in shifts in subjective scale values. The contextual effects can be interpreted as relative shifts of a number of gustatory continua, with water lying on a separate continuum. Proposed is a model for context-dependent judgments, consisting of four stages: stimulus classification, stimulus placement, continuum placement, and continuum projection.     

A behavioral link between the oculomotor and cardiovascular systems

Although the eyes and the heart serve very different purposes, each receives autonomic innervation. Capitalizing on recent theoretical and technological innovations in the understanding and assessment of oculomotor and cardiovascular behavior, three experiments measured behavioral covariation between the oculomotor and cardiovascular systems. Measures of dark focus and dark vergence indexed oculomotor tone, and the spectral decomposition of variations in heart rate indexed cardiovascular control mechanisms. In Experiment 1, individual differences in cardiovascular parameters could predict individuals’ dark vergence (R²=.806) but not their dark focus (R²=.404). In Experiment 2, the same parameters were measured from subjects who experience either panic attacks (n=11) or blood phobia (n=9). Heart rate was positively correlated with dark vergence and the two subject groups were separable based on both oculomotor and cardiovascular variables. Using a within-subjects approach, Experiment 3 found that both dark vergence and dark focus tended to be nearer during sympathetic dominance of the heart than during parasympathetic dominance, within-subjects variations in cardiovascular parameters could predict dark focus, and between-subjects variations in interbeat intervals could predict dark vergence. Shared patterns of autonomic activation may be responsible for this eye-heart link.     

Book reviews

Integrative Psychological and Behavioral Science -     

The assessment of cortisol using salivary ultrafiltrate

Cortisol can be used to indicate stress level as well as to monitor certain disease states. Although cortisol can be sampled from blood and urine, saliva sampling has decided advantages. Unfortunately, whole saliva contains a number of substances that can metabolize or bind with cortisol, potentially confounding analysis and quantitation. We introduce a semipermeable pouch that accumulates a contaminant-free salivary ultrafiltrate, thereby overcoming a number of the problems encountered with whole saliva. In three studies, we demonstrate accuracy and utility of the device for cortisol determination: (1) in an artificial medium, 60%–77% of the cortisol was recovered in the ultrafiltrate; (2) in vivo, ultrafiltrate cortisol correlated highly with whole-saliva cortisol collected under ideal conditions; and (3) ultrafiltrate cortisol evinced positive relationships with depression and cigarette use, consistent with studies in the literature. We conclude that this device and saliva-filtering technologies in general are useful in applications requiring quantitation of cortisol.     

The Fire Chief microworld generating program: An illustration of computer-simulated microworlds as an experimental paradigm for studying complex decision-making behavior

Computer-simulated microworlds bridge the gap between the complexity of field investigations and the rigor of laboratory studies. The purpose of this paper is to draw attention to the major methodological issues involved in developing and using computer-simulated microworlds for the psychological study of complex decision-making behavior. These issues comprise flexibility and generality in the microworlds that can be created, adequate psychological validity, automatic trial administration and data logging, capacity to interface simulations of psychological processes, and adequate testing and documentation. Each of these issues is illustrated by indicating how it has been addressed in Fire Chief, a microworld generating program specifically designed for creating realistic, yet controllable, decision-making task environments in the psychology laboratory. Fire Chief (Omodei & Wearing, 1993a) is introduced as both fully portable to other research teams and suitable for use in many different contexts requiring a complex task situation.     

Three- and four-year-olds’ perceptual confusions for spoken words

Although infants have the ability to discriminate a variety of speech contrasts, young children cannot always use this ability in the service of spoken-word recognition. The research reported here asked whether the reason young children sometimes fail to discriminate minimal word pairs is that they are less efficient at word recognition than adults, or whether it is that they employ different lexical representations. In particular, the research evaluated the proposal that young children’s lexical representations are more “holistic” than those of adults, and are based on overall acoustic-phonetic properties, as opposed to phonetic segments. Three- and four-year-olds were exposed initially to an invariant target word and were subsequently asked to determine whether a series of auditory stimuli matched or did not match the target. The critical test stimuli were nonwords that varied in their degree of phonetic featural overlap with the target, as well as in terms of the position(s) within the stimuli at which they differed from the target, and whether they differed from the target on one or two segments. Data from four experiments demonstrated that the frequency with which children mistook a nonword stimulus for the target was influenced by extent of featural overlap, but not by word position. The data also showed that, contrary to the predictions of the holistic hypothesis, stimuli differing from the target by two features on a single segment were confused with the target more often than were stimuli differing by a single feature on each of two segments. This finding suggests that children use both phonetic features and segments in accessing their mental lexicons, and that they are therefore much more similar to adults than is suggested by the holistic hypothesis.     

Prenatal gender preference of mothers of feminine and masculine boys: Relation to sibling sex composition and birth order

A mother's (prenatal) wish for a girl has, at times, been implicated as an etiological factor for boyhood femininity or its DSM-III-R diagnostic equivalent, the Gender Identity Disorder of Childhood. In one sample of 52 feminine and 52 nonclinical control boys from Los Angeles, the proportion of mothers who recalled a wish for a girl during the pregnancy did not differ significantly between groups (26.9% vs. 19.2%, respectively); however, in both groups, the maternal wish for a girl was significantly more common in sibships in which all of the proband's older siblings were male. In a second sample of 103 feminine boys from Toronto, the maternal wish for a girl was significantly higher than that found in the Los Angeles sample (43.7% vs. 26.9%), but a control group was not available; as in the Los Angeles sample, the maternal wish for a girl was significantly more common in sibships in which all of the proband's older siblings were male. Implications of these findings for further study of maternal influences on boyhood femininity are discussed.     

Child dissociation and the family context

Forty boys and their parents completed measures of dissociation, state anxiety, and perceptions of parental behaviors. Mothers completed a behavior problems checklist about their sons. The results indicated a correspondence between fathers' and sons' dissociation scores. In addition, links were found between parental dissociation, parental inconsistency and rejection, and child dissociation. The findings are discussed in the context of several recently proposed models of the etiology of child dissociative disorders.