Simultaneous perception of both interpretations of ambiguous figures

When viewing ambiguous figures like the classic duck/rabbit, people alternately perceive one interpretation and then the other, but not both interpretations at once. When two identical ambiguous figures appear together, the majority of observers perceive them as identical, and they typically alternate in unison. Just as most observers cannot see a single figure as both a duck and a rabbit, most cannot see one figure in a pair as a duck and the other as a rabbit even though the two figures and their features are spatially distinct. Is this inability to see both interpretations an inherent limitation of the visual system or is it just due to differences in top-down processing? We show that a simple prompt immediately allows people to see both interpretations, to their own surprise.     

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.     

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.     

Priming effects with ambiguous figures

We varied the format and semantic content of primes to determine the degree to which they would influence the interpretation of ambiguous figures. The primes were objects or object names that were related in some way to one of the two organizations of the ambiguous figures. In Experiment 1, we provided some normative data regarding the stimulus materials, whereas in Experiment 2, an orienting question was used to focus attention on the semantic relationship between the prime and the figure. In Experiment 3, we used the orienting question to divert attention away from the relationship by asking about physical features of the figures. Recognition responses to biased versions of the figures and to new figures were measured. Primes that were loosely and indirectly associated with one of the two interpretations of an ambiguous figure were found to be effective at biasing the interpretation of an ambiguous figure in the direction of the primed alternative but only if attention was focused on the semantic relationship between the two stimuli. Attention to the physical characteristics of the stimuli during encoding eliminated the prime's influence on complex object perception. These findings are consistent with the conceptual priming literature and extend those of some recent studies (Balcetis & Dale, 2007; Feist & Gentner, 2007), which show that the interpretation of complex figures can be biased by the advanced presentation of related verbal information.     

Disambiguating ambiguous figures by selective attention

The present study was designed to investigate the hypothesis that the formation of a given percept of an ambiguous figure results from focusing attention on a focal area that contains features significant for this percept but not for the alternative one. Two such focal areas were designated for the two competing interpretations of the bird/plane and duck/rabbit ambiguous figures. Detecting a letter following the figure was faster when the letter appeared in the focal area of the perceived interpretation than in the focal area of the alternative one. Furthermore, directing attention to a given focal area shortly before the presentation of the figure increased the likelihood of forming the corresponding interpretation rather than the alternative one. Results suggest that maintaining different interpretations of the same ambiguous figure is mediated by focusing attention on different parts of the figure.     

The long-term recency effect in recognition memory

Three classes of theories explain the recency effect: the modal model, single-store models, and the composite view, which integrates the two positions. None could explain the absence of a long-term recency effect in recognition memory in previous studies. We suggest that prior work did not obtain a recency effect because testing used a multiple-probe rather than a single-probe recognition procedure. Here we tested memory using a single-probe recognition procedure. Experimental conditions included an immediate test, a delayed test after a filled interval, and a continuous-distractor paradigm in which the same filled delay preceded the first word and followed every study word. The long-term recency effect in continuous-distractor recognition was equivalent to the recency effect in immediate recognition. Its absence in the delayed recognition condition demonstrated that it was not attributed to the use of a putative short-term memory store. Single-store models and the composite view can account for this novel finding.     

The first glimpse determines the perception of an ambiguous figure

The ambiguous rat-man figure was tachistoscopically presented to 36 subjects in successive segments to test the hypothesis that the starting segment would determine the perception of the figure. Starting segments were selected which were expected to produce the perception of a rat, a man, or either a rat or man. The remaining segments came from figures evaluated in a preliminary study. The selected figures differed in drawn bias and tended to be seen as a rat, a man, or either a rat or a man. The three starting segments were combined factorially with the three levels of drawn bias of the remaining segments. The effect of the starting segment was significant; the effect of drawn bias was not. A further experiment showed that presentation of the rat vs. man starting segments by themselves did not produce a reliable difference. The results support a constructive model of form perception in which the stimulus material first presented establishes a hypothesis which is used to interpret the remaining material.     

The role of discontinuities in the perception of subjective figures

Recently we proposed a theory of visual interpolation (Kellman & Shipley, in press) that addresses a variety of unit formation phenomena, including the perception of partly occluded objects and subjective figures. A basic notion of the theory is that discontinuities in the first derivative of projected edges are the initiating conditions for interpolation of boundaries that are not physically specified. In this paper, we report four experiments in which this claim was tested in the domain of subjective figures. Experiments 1 and 2 demonstrate that discontinuities in the first derivative of the edges of inducing elements have a clear effect on the frequency of report and the perceived clarity of simple subjective figures. Similar effects are found when unfamiliar subjective figures and inducing elements are used (Experiment 3). Experiment 4 rules out the possibility that the discontinuities in the first derivative merely add to the clarity of subjective figures. These experiments suggest that first-order discontinuities play a central role in unit formation.     

Children with autism's perception and understanding of ambiguous figures: Evidence for pictorial metarepresentation,a research note

A large body of autism research over the last 20 years has shown that people with autism have difficulties understanding mental states. This has been conceived of as a metarepresentational deficit. An open question is whether people with autism's metarepresentational deficit is limited to the mental domain. This research explores individuals with autism's understanding of the representational nature of pictures. With the use of ambiguous figures, where a single stimulus is capable of representing two distinct referents, we compared metarepresentational abilities in the pictorial and mental domains and the perception of pictorial ambiguity. Our findings indicate that individuals with autism are impaired in mental metarepresentation but not in pictorial metarepresentation. These findings suggest that children with autism understand the representational nature of pictures. We conclude that children with autism's understanding of the representational nature of pictures is in advance of their metarepresentational understanding of mind. Their perception of figure ambiguity is comparable to the typical population.     

Children's understanding that ambiguous figures have multiple interpretations

In three experiments we compared 5- and 6-year-old children's understanding of multiple interpretations arising from an ambiguous figure (e.g., the duck/rabbit) and other ambiguous partial input. Children found it equally easy to switch between alternative interpretations of ambiguous figures and partial views (Experiment 1, N = 19) and more difficult to accept two characters' conflicting interpretations of ambiguous figures, than partial views (Experiment 2, N = 29). Children found it more difficult to accept explicitly that one stimulus could simultaneously give rise to two interpretations, than to switch between them (Experiment 3, N = 40). Children's handling of multiple interpretations was not primarily affected by the type of input, but results suggest that there are two distinct stages in children's handling of multiple interpretations.     

Inertia and memory in ambiguous visual perception

Perceptual multistability during ambiguous visual perception is an important clue to neural dynamics. We examined perceptual switching during ambiguous depth perception using a Necker cube stimulus, and also during binocular rivalry. Analysis of perceptual switching time series using variance–sample size analysis, spectral analysis and time series shuffling shows that switching times behave as a 1/f noise and possess very long range correlations. The long memory feature contrasts sharply with the traditional satiation models of multistability, where the memory is not incorporated, as well as with recently published models of multistability and neural processing, where memory is excluded. On the other hand, the long memory feature favors the concept of “dynamic core” or coalition of neurons, where neurons form transient coalitions. Perceptual switching then corresponds to replacement of one coalition of neurons by another. The inertia and memory measures the stability of a coalition: a strong and stable coalition has to be won over by another similarly strong and stable coalition, resulting in long switching times. The complicated transient dynamics of competing coalitions of neurons may be addressable using a combination of functional imaging, measurement of frequency-tagged magnetoencephalography and frequency-tagged encephalography, simultaneous recordings of groups of neurons in many areas of the brain, and concepts from statistical mechanics and nonlinear dynamics theory.     

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.     

Area perception in simple geometrical figures

The results of experiments on visual perception of area of circles and squares are reported. Pairs of geometrical figures were presented simultaneously on an oscilloscope screen. While one of them was fixed, the other one was controlled by an experimental subject. The task of the subject was to match the area of the variable figure to the area of the fixed one. The obtained data show underestimation of the area of circle when compared with square. A mathematical model designed to explain this phenomenon is proposed here. The image function defined as a low-pass filtered (blurred) version of the figure is employed for this purpose. Then, instead of the position of the image function maxima, the position of a threshold value is used for area computation.