Perceptual ambiguity and stability of reversible figures

In this work, the results of two experiments on ambiguous patterns are reported, which have been obtained by presenting a series of stimuli designed, in both cases, to reduce gradually the ambiguity of the patterns. Such reduction has been performed by respectively increasing or decreasing the amount of graphic details in the experiments. Data of both experiments show a lengthening of mean reversal time. The increase in the stability of one percept can be regarded as associated with the increasing difficulties encountered by an observer in organizing and restating the alternative "hypothesis" through the perceptual mechanisms. The loss of balance in the durations of percepts is discussed in terms of their different informational contents. Finally, in Exp. 1 an analysis is made to evaluate to what extent an addition of perceptual cues, designed to reinforce a three-dimensional interpretation of a pattern, can influence its figure-ground alternation.     

Ambiguous benefits: the effect of bilingualism on reversing ambiguous figures

Two studies are reported in which monolingual and bilingual children, approximately 6 years old, attempted to identify the alternative image in a reversible figure. In both studies, bilingual children were more successful than monolinguals in seeing the other meaning in the images. In the first study, there was no relation between the ability to reverse the interpretation and performance on the children's embedded figures task, a task that superficially appeared to involve similar processes. The second study replicated this finding but showed that performance was strongly related to success in the post-switch phase of the dimensional change card sort task. In both cases, the meaning of an image must be reassigned, and bilinguals were better in both these tasks.     

The effect of knowledge of reversibility on the reversibility of ambiguous figures

The role of knowledge of the reversibility of reversible figures was tested in four experiments. Two ambiguous figures, the vase-face figure and a depth-reversing pyramid-hallway figure were shown to high school students. In the Uninformed condition, subjects were not told that the figures were reversible. A sampling procedure was used in which subjects reported what they perceived at 5-sec intervals. Viewing durations of up to 3 min were used, and approximately half of all subjects did not reverse at all during the uninformed condition, whereas virtually all subjects reversed quickly and frequently once they knew that the figures were reversible. These results are not consistent with neural fatigue models of perceptual reversal.     

Effects of sleep deprivation on voluntarily controlled reversal rate of ambiguous figures

Abstract.— The effects of sleep deprivation (SD) on the reversal rate of the Necker cube and Rubin's Vase-Faces were studied both with instructions to maximize and to minimize the rate. Three viewing conditions were used: Free eye movements, eyes on a fixation point and reversals of an after-image of the figure. SD was found to increase the rate under minimizing instructions and to decrease the rate under maximizing instructions. The results were interpreted in terms of an accelerated satiation process and an impairment of the attentional control.     

The relationship between bilingualism and selective attention in young adults: Evidence from an ambiguous figures task

Previous research has shown that bilinguals outperform monolinguals on a variety of tasks that have been described as involving executive functioning, but the precise mechanism for those effects or a clear definition for “executive function” is unknown. This uncertainty has led to a number of studies for which no performance difference between monolingual and bilingual adults has been detected. One approach to clarifying these issues comes from research with children showing that bilinguals were more able than their monolingual peers to perceive both interpretations of an ambiguous figure, an ability that is more tied to a conception of selective attention than to specific components of executive function. The present study extends this notion to adults by assessing their ability to see the alternative image in an ambiguous figure. Bilinguals performed this task more efficiently than monolinguals by requiring fewer cues to identify the second image. This finding has implications for the role of selective attention in performance differences between monolinguals and bilinguals.     

Behavioral,subjective, and electroencephalographic indices of sleep onset latency and sleep duration

Electrographic (EEG, EOG, EMG) indices have been used for some decades in the definition of the stages of sleep and more recently in the diagnosis of sleep-related disorders, e.g., insomnia, despite the lack of detailed information concerning the precise relationship between such electrographic indices and behavioral and subjective criteria of sleep. Evaluation of the relationship between EEG, behavioral, and self-report measures of sleep onset latency and sleep duration was conducted using 17 young normal sleepers. The behavioral measure was provided by an apparatus which records subjects' button-press responses to an auditory stimulus presented at various interstimulus intervals (2, 5, and random 1, 2, 5, 7, and 10 min). The behavioral and stage 2 EEG estimates of sleep onset latency (SOL) and sleep duration (SD) were almost identical. The stage 1 EEG provided the shortest estimate of SOL; the self-report measure, the longest. The SD measures were in reverse order. There were no significant differences among the three interstimulus interval conditions (2, 5, and random min). Average response rates to the 50-dB chime were 100% during wakefulness, 81% during EEG stage 1, and 8% during EEG stage 2. Almost all stage 2 responding occurred during the first 5 min of each stage 2 period. The validity of electrographic indices as sleep criteria and the implications of the findings for the formulation of an adequate definition of sleep and its clinical measurement are discussed.     

Ambiguity and structural information in the perception of reversible figures

The perspective reversals elicited by a set of drawings based on the Mach truncated pyramid are examined. We obtained each pattern of the set from the previous one by adding to it some graphic cues, which were easily integrated into one of the two competing interpretations, thus reducing step by step the ambiguity of the basic pattern. The phenomenological model, proposed to link the mean times of both alternative interpretations with their complexities, is in close agreement with our experimental data. Furthermore, different aspects of such data are well described by the model equations: The measure of the prevalence of the supported interpretation is well correlated with the difference in complexity between the two alternative interpretations; the two different trends of the mean time of the unfavored interpretation, found in the data obtained from different observers as a function of the various patterns of the set, are well fitted by the model without the need for any specific additional hypothesis.     

Comparisons of second-generation holocaust survivors, immigrants, and nonimmigrants on measures of mental health

To determine whether a "children-of-holocaust-survivors syndrome" could more parsimoniously be explained as an "immigration effect," we performed a comparative study on a sample of 25 children of holocaust survivors, 25 children of immigrants, and 25 children of American-born parents. Subjects were matched on age and educational level and were assessed with four measures of mental health. Contrary to the findings of some researchers whose data supported such a syndrome, our data indicate no significant differences between children of holocaust survivors and the children of other immigrants. These data are suggestive of an immigration effect that is common to the children of immigrants and not limited to the children of holocaust survivors, rather than a survivors syndrome. The children of American-born parents showed greater alienation, less religiosity, and a tendency toward feelings of less guilt than the other two groups. Our data underscore the need to control immigrant status in multiple samples and studies before definitive conclusions can be drawn in this area.     

The precision of latency measures on real-time computing systems

We derive expressions for the bounds on the precision of response latency measures made using a free-running digital clock and discuss other possible sources of measurement errors. In a multitask, real-time environment, there are three possible sources of large measurement errors: (1) the finite resolution of the digital clock, (2) unscheduled delays in recording the time of occurrence of an event, and (3) the uncertainty of the time of stimulus presentation for stimuli presented on a CRT terminal.     

Risk perception in novice drivers: the relationship between questionnaire measures and response latency

The extent to which questionnaire based measures of driving risk, driving ability and accident likelihood are associated with response latency based measures obtained on a hazard perception test was examined. In Experiment 1 questionnaire evaluations of driving in general were obtained and correlated with hazard perception performance. In Experiment 2 questionnaire evaluations and hazard perception performance were obtained when drivers viewed the same driving scenes. In neither experiment did questionnaire responses correlate significantly with hazard perception performance. Additionally while in both experiments no difference in hazard perception performance arose between males and females, females rated driving as more risky and their ability to be lower than males. The results indicate independence between questionnaire and response latency measures of hazard perception. However the possibility that both approaches should be adopted within a single framework is raised.     

Configural biases and reversible figures: evidence of multilevel grouping effects

Four experiments sought to identify the processes underlying 2 classes of grouping effects that are readily produced with a hierarchical figure type known as ambiguous triangles. Previous work has shown that aligning small equilateral triangles in particular configurations can both facilitate and interfere with observers' ability to report the pointing direction of the individual triangles. We determined that selectively adapting the observer to low-frequency gratings of the same orientation as the aligned triangles markedly altered the interfering and facilitative effects of the global configuration only when an accuracy measure of performance was used. When a response latency measure was used, no effect of the same adaptation condition was found. Results are discussed in terms of multiple levels of grouping effects in the visual system and the differential sensitivity of these levels to basic neural adaptation.