Acceleration of Reversals of a Necker Cube

125

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.Ambiguous figures and the perceptual alternations which occur when viewing them are of interest because their explanation would appear to require central dynamic factors. Previous reports and theories have repeatedly stressed the spontaneous character of the reversals in which voluntary control neither causes nor prevents reversal. This apparent spontaneity of reversals has played an important role in the theoretical interpretation of the phenomena. The most widely investigated theory, the cortical satiation theory of Kohler and Wallach (1944), proposed that cortical' events produce their own resistance and bring about their automatic replacement by the opposing cortical events that then result in the perceptual reorganization. But all fatigue or satiation theories of reversal, including those based on contemporary neurophysiological constructs, posit an inexorable effect due to continuous passive stiniulation.This kind of theory of reversal implicitly defines ambiguity purely in stimulus terms. The stimulus can represent two (or more) possible objects, and when one such percept is satiated another automatically replaces it. Of course, this presupposes that the observer can identify these alternatives either because each is a familiar object (e.g., "cube," "face," "vase," etc.) or because each is a member of a different category or distinctive in some way in the observer's repertoire (e.g., "cube tipped up or on edge," "two-dimensional line pattern," etc.) But one might ask the further question of whether the meaning of ambiguity presupposes awareness by the observer that the figure is ambiguous. This is the issue with which we are concerned here. There is nothing in the literature to suggest that such awareness is part of 'the meaning of ambiguity and, in fact, it seems to be implicit that such knowledge is not a necessary part of the meaning. Certainly such an assumption is alien to the satiation model for the reasons 550 suggested above.Nonetheless, experiments on figure reversal are performed with informed subjects. The method typically employed in studying this problem seems necessarily to entail informing the subject about the possible alternative perceptions of a given figure, and that the figure reverses. It is understandable why investigators have believed that only in this way ...

Section: Discussionmentioning

confidence: 99%

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

Girgus

Rock

Egatz

1977

125

“…The influence of such processes has been demonstrated in the results of numerous studies. These include, to name just a few, findings that observers may fail to perceive reversals if they do not know that the stimuli are reversible (Girgus, Rock, & Egatz, 1977;Rock & Mitchener, 1992), that the rate at which reversals are perceived increases as a function of learning (Long, Toppino, & Kostenbauder, 1983), and that observers can exert intentional control over the perception of reversible figures (e.g., Liebert & Burk, 1985;Pelton & Solley, 1968).…”

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confidence: 99%

Reversible-figure perception: Mechanisms of intentional control

Toppino

2003

116

127

Observers can exert a degree of intentional control over the perception of reversible figures. Also, the portion of the stimulus that is selected for primary or enhanced processing (focal-feature processing) influences how observers perceive a reversible figure. Two experiments investigatedwhether voluntary control over perception of a Necker cube could be explained in terms of intentionally selecting appropriate focal features within the stimulus for primary processing. In Experiment 1, varying observers' intentions and the focus of primary processing produced additive effects on the percentage of time that one alternativewas perceived. In Experiment 2, the effect of varying the focus of primary processing was eliminated by the use of a small cube, but the effect of intention was unaltered. The results indicate that intentional control over perception can be exerted independently of focal-feature processing, perhaps by top-down activation or priming of perceptual representations. The results also reveal the limits of intentional control.

“…In fact, the two general classes of explanations of reversible figures have impressive empirical support that has taken several forms. For example, the role of cognitive processes would appear to be required by the findings that instructions to observers can significantly alter reversal rates of subsequently viewed figures (Hochberg & Peterson, 1987;Liebert & Burk, 1985;Pelton & Solley, 1968). The demonstrations that the presence of a distractor task slows the rate of perceived reversals (Reisberg, 1983;Reisberg & O'Shaughnessy, 1984) and that, unless observers know that the figures being viewed are reversible, they may fail to perceive any reversals at all (Girgus et al, 1977) are also difficult to…”

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confidence: 99%

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

Long

Toppino

Mondin

1992

115

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 ofthe preceding prime following briefpreexposure 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.