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.     

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 teacher attention on digit-reversal behavior in an elementary school child

Teacher attention was systematically manipulated to modify digit-reversal behavior in an elementary school child. Almost invariably, the child reversed the order of digits (e.g., writing 21 as the sum of 5 + 7) when adding numbers yielding a two-digit sum. The child, along with classmates, was given 20 addition problems a day for the duration of the study, and the number of reversals was recorded. During an initial baseline period, the teacher responded to digit reversals by marking them as incorrect and then giving the child "extra help" until all sums were correctly ordered. The child's present and previous teacher had both responded to reversals in this manner for approximately one year before the present study began. An experimental period followed during which the rate of reversals decreased sharply. During this period, all sums were marked as correct (whether reversed or not); "extra help" with reversals was discontinued; and correct, i.e., non-reversed, response forms were responded to with a smile, a pat on the back, and a brief comment. A reversal period followed, during which the teacher responded to reversals as she had in the first baseline period. An increase in the rate of reversals to baseline level occurred within three days. A final period, replicating the first experimental period followed, and was characterized by a sharp decrease in the rate of reversals.     

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).     

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.     

Ambiguous figure perception and theory of mind understanding in children with autistic spectrum disorders

Researchers in early social‐cognition have found that the ability to reverse an ambiguous figure is correlated with success on theory of mind tasks (e.g. Gopnik & Rosati, 2001 ). The present experiment examined children with autistic spectrum disorders (ASD) without mental delay to see whether a similar relationship existed. Ropar, Mitchell, and Ackroyd (2003) demonstrated that children with ASD with mental delay were impaired on theory of mind tasks, but were as likely as mentally delayed controls to generate both interpretations of an ambiguous figure when informed of its ambiguity. The present study replicated this finding on children with ASD without mental delay. However, overall perception of ambiguous figures was different. These children were less likely to spontaneously generate both interpretations of the figure, and more likely to perseverate on a single interpretation than the comparison children. Like Ropar et al., we found no correlation between theory of mind and informed reversals, but spontaneous reversals were correlated with performance on an advanced theory of mind task. These data suggest that reversals of ambiguous figures are linked to higher‐level representational abilities, which might also be involved in social functioning, and impaired in children with ASD.     

An investigation of reversal learning in octopus vulgaris lamarck

Eighteen octopuses were trained by a method of successive discrimination training to discriminate between a vertical and a horizontal rectangle. They were then overtrained for either 20 or 60 trials, after which they learnt the reverse discrimination. At the beginning of each reversal they were given 20 trials pretraining on the new positive stimulus. The subjects completed from two to nine reversals.

It was found that the amount of overtraining had no effect on the rate of learning the subsequent reversal. The first four reversals all took significantly longer to learn than the original problem, but did not differ significantly from one another. However, examination of the raw data suggests that later reversals do take longer to learn. The performance when learnt (i.e. on the first day of overtraining) was as good after reversal learning as after the learning of the original problem.

The results do not show definite signs that could be interpreted as an exhaustion of a limited supply of neurones available for learning.     

Occurrence of theoretically correct responses during rotation of the Ames window

It has been hypothesized (Graham, 1963) that reversals in the Ames window are the outcome of a resolution of ambiguous differential angular velocity cues by linear perspective cues. This theory was tested. A parallel projection of the window on an opal glass screen was used as the stimulus. Ss almost always reported two apparent reversals per rotation. The long vertical side of the figure was always apparently in front of the short vertical side. These results were interpreted to be in line with theoretical expectations.     

The relationship of target and response complexity in coincident timing performance

This paper reports two experiments concerned with the interaction of response and target factors in a coincident timing situation. Coincident timing involves executing a response to intercept a moving target. The target response relationship was manipulated in the first experiment by providing some targets with no structure (linear path) and others containing 1 and 2 bounce points. In the second experiment, responses required 0, 1, or 2 reversals in direction. The results provide tentative support for the notion that structure in the target path could be linked to the key temporal response dynamics for improved performance consistency, and that subjects may alter their response structure to incorporate this linkage. This can be further extended to the advantage of simply moving while perceiving movement. This paper stresses the importance of examining the perceptual and motor requirements of the coincident timing skill in unison.     

The Relationship of Target and Response Complexity in Coincident Timing Performance

This paper reports two experiments concerned with the interaction of response and target factors in a coincident timing situation. Coincident timing involves executing a response to intercept a moving target. The target response relationship was manipulated in the first experiment by providing some targets with no structure (linear path) and others containing 1 and 2 bounce points. In the second experiment, responses required 0, 1, or 2 reversals in direction. The results provide tentative support for the notion that structure in the target path could be linked to the key temporal response dynamics for improved performance consistency, and that subjects may alter their response structure to incorporate this linkage. This can be further extended to the advantage of simply moving while perceiving movement. This paper stresses the importance of examining the perceptual and motor requirements of the coincident timing skill in unison.     

The effect of reduced spatial cues on the learning of successive visual reversals

The performance of rats over 12 brightness discrimination reversals was studied under two experimental conditions. Under one condition all visual cues external to the apparatus were eliminated so that only the relative positions of the discriminanda could serve as a visual cue to spatial position. Under the other condition all visual cues to position were eliminated. Under the former condition performance deteriorated with successive reversals but under the latter condition performance improved. Implications of these results for theories of successive reversal improvement were discussed and two possible explanations were suggested.     

Multistable perception: when bottom-up and top-down coincide

During prolonged observation of an ambiguous figure sudden perceptual reversals occur, while the stimulus itself stays unchanged. There is a vivid debate about whether bottom-up or top-down mechanisms underlie this phenomenon. In the present study, we investigated the interrelation of two experimental factors: volitional control and discontinuous stimulus presentation. Both factors strongly modulate the rate of perceptual reversals and each is attributed either as top-down or bottom-up. We found that participants can apply specific strategies to volitionally increase and/or decrease the stability duration of each of the possible percepts according to the experimental instructions. When attempts of volitional control are combined with discontinuous stimulus presentation the effects are fully additive. Our results indicate that perceptual reversals can originate from different neural mechanisms on different time scales.     

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.     

Orientation selectivity in infancy: behavioural evidence for temporal sensitivity.

One-month-old infants were tested with a habituation-recovery paradigm to determine whether they could discriminate phase-shifting grating patterns that switched between two orientations, three or eight times a second, from grating patterns that only shifted in phase. The infants were found to discriminate patterns switching orientation at the lower temporal rate of 3 reversals s-1, but not 8 reversals s-1. This finding supports the idea that orientation-selective mechanisms improve in their temporal sensitivity during early infancy. Where they can be compared, the results from behavioural and electrophysiological studies agree as to the course of this development.     

Parallel processing in visual same-different decisions

Two to 13 geometrical shapes were exposed simultaneously to S who decided whether all shapes were the same or whether one was different from the rest. Correct different decisions were usually faster than correct same decisions, but latency was independent of the number of shapes presented. We conclude that input from all the shapes was simultaneously processed into either one or two shape categories, and that a decision-theory choice was made between “same” (one shape category) and “different” (two shape categories) independent of the total number of shapes. This parallel processing is thought to be a characteristic of codable stimuli. Some observed same-different latency reversals were probably caused by a shift in the same-different criterion on the continuum for one- vs two-category decisions.     

To reverse or not to reverse: when is an ambiguous figure not ambiguous?

The role of bottom-up processes in our perception of reversible figures was examined. In Experiment 1 the overlapping squares figure and nonsense reversible figures were used. The effects of adapting subjects for differing durations to an unambiguous version of the figure before presentation of the traditional reversible figure were determined under conditions of varying precision of fixation. In Experiment 2 the research was expanded to other examples of reversible figures. In both experiments, results with two dependent measures (the subject's first percept and the number of reversals reported) were generally consistent with the interpretation of bottom-up processes underlying the adaptation effects. However, the crucial role of stimulus and procedural variables and the differential sensitivity of the two dependent measures was demonstrated.     

Analyzing nonverbal listener responses using parallel recordings of multiple listeners

In this paper, we study nonverbal listener responses on a corpus with multiple parallel recorded listeners. These listeners were meant to believe that they were the sole listener, while in fact there were three persons listening to the same speaker. The speaker could only see one of the listeners. We analyze the impact of the particular setup of the corpus on the behavior and perception of the two types of listeners: the listeners that could be seen by the speaker and the listeners that could not be seen. Furthermore, we compare the nonverbal listening behaviors of these three listeners to each other with regard to timing and form. We correlate these behaviors with behaviors of the speaker, like pauses and whether the speaker is looking at the listeners or not.