Hypnotic susceptibility, interference, and alternation frequency to the Necker cube illusion

Two experiments (N = 60) were conducted to determine the effects of hypnotic susceptibility and interference on frequency of Necker cube apparent reversals (ARs). Interference was induced in Experiment 1 by having subjects respond to orally administered double-digit arithmetic (addition) problems while observing the Necker cube. In Experiment 2, counting backward by 3s served as interference. In both experiments, interference reduced ARs. Hypnotic susceptibility level also influenced ARs, with those scoring high on this attribute reporting more ARs than those scoring low. Attentional factors may have played a major role in producing the reported results.     

Hemispheric dominance inferred from Your Style of Learning and Thinking on reports of Necker cube reversals and maze learning

30 subjects volunteered from three sources: community adults (M age = 32.8, SD = 13.4), college adults (M age = 23.8, SD = 8.3), and children (M age = 9.5, SD = 1.7) and were categorized as 'left-' and 'right-dominant' by scores on Your Style of Thinking and Learning. They reported the number of Necker cube reversals perceived in 90 sec., attempted to locate four embedded figures, and blindly traversed a 16-choice point finger maze in that order. 'Right-dominant' subjects located more embedded figures and made fewer errors on the finger maze than did 'left-dominant' subjects. College adults reported more Necker cube reversals than did community adults and children, and community adults reported more reversals than did children. Confounds of performance measures with fatigue and/or practice require further research.     

Differences in top-down influences on the reversal rate of different categories of reversible figures

Understanding the mechanisms underlying the multistability of reversible figures may provide valuable insights into the normal functioning of our visual system. The proposed factors that control the perceptual alternations of reversible figures can be classified into bottom-up and top-down processes. In the present study, we report differences in top-down effects on the reversal rate depending on whether a structural perspective (Necker cube, Schr?der staircase) or a meaningful content (duck/rabbit figure, chef/dog figure) is subject to the reversal phenomenon. In order to activate top-down mechanisms explicitly the subjects had the instruction to bring the reversal rate under voluntary control. The results indicated that both slowing down and speeding up the rate of alternations was more effective for the content-reversal figures (duck/rabbit, chef/dog) than for the rather abstract perspective-reversal figures (Necker cube, Schr?der staircase). In order to investigate the effect of meaningfulness in figure/ground reversals, the effect of the same instructional variable was also determined for Rubin's vase/faces and the Maltese cross. The results showed a similar tendency as in the case of the comparison between perspective reversals and content reversals. Possible cognitive processes that may play a role in top-down influences on figure reversal and theoretical implications of these findings for the interaction of bottom-up and top-down processes are discussed.     

Assessing executive abilities following acute stroke with the trail making test and digit span

The Trail Making Test and Digit Span are neuropsychological tests widely used to assess executive abilities following stroke. The Trails B and Digits Backward conditions of these tests are thought to be more sensitive to executive impairment related to frontal lobe dysfunction than the Trails A and Digits Forward conditions. Trails B and Digits Backward are also thought to be more sensitive to brain damage in general. Data from the Stroke and Lesion Registry maintained by the Washington University Cognitive Rehabilitation Research Group were analyzed to compare the effects of frontal versus nonfrontal strokes and to assess the effects of stroke severity. Results showed that the performance of patients with frontal and nonfrontal strokes was comparable in each condition of both the Trail Making Test and Digit Span, providing no support for the widely held belief that Trails B and Digits Backward are more sensitive to frontal lobe damage. Further, Trails A was as strongly correlated with stroke severity as Trails B, whereas Digits Backward was more strongly correlated with stroke severity than Digits Forward. Overall, the Trail Making Test and Digit Span are sensitive to brain damage but do not differentiate between patients with frontal versus nonfrontal stroke.     

Perceptual exploration and intersensory merging in a visual–haptic Necker cube

Background

Perceiving the three-dimensional structure of an object often involves merging vision and haptics over extended periods of exploration. An interesting feature of this process is that as exploration progresses, new information may require changing how the two sensory signals are treated.

Aims

We tested whether (1) bimodal interactions during extended observation can adjust to changes in the quality of unimodal sensory signals; and (2) there are specific temporal constraints on these adjustments.

Methods

When viewing a three-dimensional Necker cube with one eye, participants experience illusory reversals even while they feel the cube with their hands. This surprising property makes the visual–haptic Necker cube an excellent model to investigate bimodal processes when previously consistent bimodal signals change in quality over time or begin to conflict. Our participants reported reversals while they viewed the cube and, at the same time, they either held it with two-finger grips, felt it with while their hands remained stationary, or actively explored it by moving one hand.

Results

Consistent with a multisensory approach to three-dimensional form perception, touch had a clear effect on both the number and the duration of illusory percepts. Additionally, when observers alternated between stationary and moving periods during exploration, transitions from stationary to moving-hand haptics played a crucial role in inhibiting illusory reversals. A temporal analysis of the probability of first reversals occurring after different types of motor transition revealed a “vetoing window” initiating approximately 2 s after the transition and lasting at least another 1–2 s.

Conclusions

These results suggest that intersensory merging is sensitive to changes in the quality of unimodal signals during exploration, and that adjustments caused by these changes are characterized by specific temporal dynamics.

     

EEG gamma-band response during the perception of Necker cube reversals

In two former studies our research group reported frontal gamma-band enhancement during multistable visual perception and reversal rate dependent differences in the gamma-band. In these studies, a dynamic reversible figure was used which was based on the phenomenon of apparent motion. The aim of this study was to examine whether the results obtained with a dynamic motion paradigm can be replicated with the static Necker cube. The results demonstrate a general frontal gamma-band enhancement and higher induced gamma activity for subjects with a relatively high reversal rate in comparison to subjects with a relatively low reversal rate. This pattern of results fits well to the findings obtained with the dynamic motion paradigm. Therefore, the important role of frontal gamma activity for figure reversals has received further evidence. The results support the involvement of attentional top-down processing of figure reversal that is not directly related to binding processes.     

Selective adaptation with reversible figures: Don’t change that channel

An adaptation-test paradigm was used in two experiments examining processes underlying the perceived reversals of a rotating Necker cube. Adaptation and test cubes were either the same or different with respect to their visual fields of presentation (Experiment 1) or their sizes (Experiment 2). Results of both experiments indicated that, following subjects’ adaptation to a different cube, reversal rate of the test cube did not differ from that obtained without prior adaptation experience. In contrast, reversal rate of the test cube was elevated following adaptation to the same cube. Additional findings of Experiment 1 were that a test cube presented to the same visual field as the adaptation cube yielded a higher reversal rate than did a simultaneously presented cube in the opposite visual field. Also, the reversal rate of one cube was not influenced by the simultaneous presentation of a second cube. Results of both experiments were interpreted in terms of the fatigue and recovery of multiple, largely independent, localized neural channels. Thus, the results tie reversible-figure illusions to other visual phenomena thought to involve similar fatigue processes within localized visual channels (e.g., tilt, motion, and size aftereffects).     

Prime time: fatigue and set effects in the perception of reversible figures.

Subjects viewed unambiguous versions of both stationary and rotating Necker cube illusions for varying durations prior to the presentation of the standard ambiguous figure. In each case, the subjects were more likely to report the ambiguous figure to be (1) in the same configuration as that of the preceding prime following brief preexposure periods and (2) in the opposite configuration from that of the preceding prime following long preexposure periods. In addition, the number of reversals of the figure during the test period was also strongly related to the duration of the preexposure period, with progressively fewer reversals reported following longer preexposure periods. The results are interpreted as revealing the concurrent roles of "set" effects in the brief preexposure conditions and neural fatigue effects in the long preexposure conditions. Furthermore, the ability of the proposed two-process model to integrate the myriad of empirical effects in the reversible-figure literature is emphasized.     

Prime time: Fatigue and set effects in the perception of reversible figures

Subjects viewed unambiguous versions of both stationary and rotating Necker cube illusions for varying durations prior to the presentation of the standard ambiguous figure. In each case, the subjects were more likely to report the ambiguous figure to be (1) in the same configuration as that of the preceding prime following brief preexposure periods and (2) in the opposite configuration from that of the preceding prime following long preexposure-periods. In addition, the number of reversals of the figure during the test period was also strongly related to the duration of the preexposure period, with progressively fewer reversals reported following longer preexposure periods. The results are interpreted as revealing the concurrent roles of “set” effects in the brief preexposure conditions and neural fatigue effects in the long preexposure conditions. Furthermore, the ability of the proposed two-process model to integrate the myriad of empirical effects in the reversible-figure literature is emphasized..     

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.     

As the cube turns: Evidence for two processes in the perception of a dynamic reversible figure

The reported reversals of a rotating Necker cube, which changes direction of rotation when a perspective reversal occurs, were examined under a number of conditions. These permitted comparisons of reversal rates within viewing periods, across successive viewing periods within an experimental session, and across successive weekly sessions. In addition, observers viewed either one or two rotating cubes simultaneously within each of the various viewing periods. Clear evidence for a learning effect was obtained in the form of significant savings across successive viewing periods and sessions. At the same time, results from the multiple-cube conditions and from the pattern of reversals within individual viewing periods appeared to be more consistent with a process of neural fatigue. A two-stage model of reversible-figure perception is proposed which is characterized by (1) fatiguing with extended viewing of the two sets of neural channels that underlie the two percepts of the reversible figure, and (2) learning, which helps to establish the organization of the cortical channels as well as moderate channel activity via such processes as attention and strategy.     

Hypnotic susceptibility, visual distraction, and reports of Necker cube apparent reversals

Subjects, either susceptible (n = 50) or resistant (n = 50) to hypnotic suggestion, were asked to report on frequency of apparent reversals (ARs) to the Necker cube illusion. Such reports were made in the presence or absence of various types of visual, geometric surrounds (squares, triangles, crosses, or parallelograms). In agreement with a number of previous experiments, susceptible subjects reported perceiving more ARs than did resistant subjects. This difference held whether visual surrounds were present or absent. The presence of surrounds did serve to reduce AR reports regardless of hypnotic susceptibility level. The results are examined in terms of the ability of subjects to selectively attend when confronted with potential visual distractors.     

Perceived depth inversion of smoothly curved surfaces due to image orientation

A relative depth judgement task was used to distinguish perceived reversals in depth due to image orientation from spontaneous reversals such as those observed with a Necker cube. Results demonstrate that inversion effects due to image orientation can occur for several different types of pictorial representation and that many of these effects are incompatible with traditional explanations involving a perceptual bias for overhead illumination. When this bias was neutralized by placing the light source at the point of observation, the effects of image orientation were just as large as with overhead illumination. Similar results were also obtained for surfaces depicted with texture or motion in which all relevant shading information was eliminated. These results can be explained by a perceptual bias for backward slanting surfaces, but additional evidence suggests that this bias can be attenuated by the presence of smooth occlusion contours.     

Lack of association between negative priming and Necker Cube reversals

50 undergraduates were tested on two tasks presented in a counterbalanced fashion: their ability to inhibit irrelevant information measured on a negative priming task involving letter case information and on the number of Necker Cube reversals produced in a specific time period. Since number of reversals presumably reflects a person's ability to see various interpretations of the Necker Cube, this assumes that multiple interpretations are available to a subject and no one interpretation dominates over another. If true, then more reversals could indicate an ability to inhibit irrelevant information. That is, observing one reversal at the expense of another reversal indicates a subject can adequately inhibit these various interpretations successfully, with more reversals indicating a higher ability to inhibit information successfully. Although it was predicted that negative priming performance would be related to the number of Necker Cube reversals, this was not the case (r = -.07).     

Normative data for a brief neuropsychological screening battery. Multicenter AIDS Cohort Study.

This study reports normative data for a group of 733 homosexual/bisexual men stratified by age (range 25 to 54 years) and by education on the following six neuropsychological tests: (1) Digit Span (WAIS-R), (2) Rey Auditory Verbal Learning Test, (3) Symbol Digit Modalities Test, (4) Controlled Oral Word Association Test, (5) Grooved Pegboard, and (6) The Trail Making Test. Analysis demonstrates that both age and education are important determinants of performance for several of these measures.     

Predictive factors of manual dexterity and cognitive performance at 17 years: a 10-year longitudinal study in a rural area of France

Studies of predictive factors of manual dexterity in adolescents and young adults are lacking. The present longitudinal study reports the relationship between cognitive and behavioural assessments at age 7 years and the schooling, cognitive performance, and manual dexterity at age 17 years. The participants were 65 schoolchildren, 30 boys and 35 girls, from a rural area in France. Assessment at age 7 years included the McCarthy scales and questionnaires measuring the behavior of the child, completed by the mother, the teacher, and the assessing psychologist. Assessment at age 17 years included schooling situation (whether they were in high school or not), cognitive testing (WAIS-R, Trail Making, Verbal Fluency, Cancel H, Stroop, Memory Assessment Scales), and manual dexterity testing (dynamometer, Finger Tapping, Santa Ana Test, Purdue Pegboard). After controlling for effects of parental education and IQ, a negative teachers' rating of children's behaviour and abilities in first-grade (7 years) was correlated with early cessation of schooling, but also, unexpectedly, with higher scores for manual dexterity at 17 years. Manual dexterity was not related to cognitive performance at 17 years. It is suggested that the relationship between manual and cognitive performance varies during development. Although manual exploratory behaviour is an important correlate of early cognitive development, manual dexterity is probably not related to later academic performance.     

Finger tapping: effects of trials and sessions

18 normal, self-reported dextral subjects (9 men, 9 women) were assessed with a Halstead Manual Finger Tapping device, with 10 trials per hand for 10 consecutive wk. The test-retest reliability of the 10-trial average between the 10 sessions averaged .94 for men and .86 for women, for both preferred and nonpreferred hands. There were no statistically significant effects of increases in performance over sessions or effects of fatigue over trials for either sex or hand. There were, however, significant increases over trials for men for both preferred and nonpreferred hands.     

Independent perceptual reversals for simultaneously presented ambiguous figures

In two successive experiments using the divided visual field paradigm with vertical or horizontal division, two ambiguous figures, the Rubin’s vase-face or the Necker cube, were projected to the right and left or to the upper and lower visual hemifields of 108 healthy volunteers. Stimulation time was 120 s. The main hypotheses were (a) that different percepts of the same ambiguous figure may be simultaneously experienced in the two hemifields and (b) that the type (vertical vs. horizontal) of visual field division influences the reversal frequency and the temporal interdependence of the percepts.Results from the first experiment showed that the temporal interdependence of reversals was very low for both ambiguous figures, suggesting that during part of the stimulation time the subjects could experience different percepts of the same figure (e.g. a vase in the right and face profiles in the left visual hemifields). The second experiment showed that this perceptual dissociation occurred on average during one third of the stimulation time. In both experiments the type of visual field division did not influence either frequency or temporal interdependence of the reversals. When one single ambiguous figure was presented in the centre of the screen, the number of reversals was approximately the sum of the reversals observed with two figures presented simultaneously each in one hemifield.     

Viewing direction and pictorial representation

During prolonged monocular observation from afar, an upright wire cube (Necker cube) or a drawing of such a cube inverts continuously so that the lower of the two frontal faces appears to be either in front (version A) or in back (version B). Version A is perceived as if it were viewed obliquely from above and version B as if seen from below. In our experiments, timing the durations of the versions showed that version A lasted longer than version B. When a wire cube was shifted upward so that it was actually viewed slightly from below, version B lasted longer than version A. The actual viewing direction was apparently taken into account by the subjects, which was not the case when the cube was replaced by a drawing showing the projection of the cube. In that case, version A always lasted longer, regardless of the actual viewing direction. This finding conforms with picture viewing in general, where a three-dimensional object’s orientation does not change when the observer’s viewing direction changes.     

Comparison of the Trail Making and Color Trails Tests in a Chinese context: a preliminary report

The Color Trails Test developed as a culturally fair analogue of the Trail Making Test, was used to examine the relationship between the two tests with 35 undergraduate Chinese in Hong Kong recruited as the subjects. The scores on these two tests of the 12 men and 23 women were significantly correlated .71. The equivalence of the Trail Making and Color Trails Tests when applied to Chinese in Hong Kong was discussed.