How to keep a reversible figure from reversing: teasing out top-down and bottom-up processes

The nature of processes underlying our perception of reversible figures was examined through two experiments investigating the effects of prior exposure conditions on an observer's report of figural reversal. In experiment 1, observers were adapted over several minutes to an unambiguous version of a rotating Necker cube prior to the presentation of the standard ambiguous figure. Results indicated that adaptation produced an immediate bias to perceive the ambiguous figure in the opposite configuration (ie reverse bias) and to reduce reports of reversal over the test period. The introduction of a brief delay between the adaptation and test periods revealed that this bias is a highly transient effect and is only clearly evident when the adaptation and test figures are matched in size. In experiment 2, observers were primed with an unambiguous figure for a few seconds prior to the presentation of the standard ambiguous figure. In this case, the obtained bias strongly favored the observer's reporting the ambiguous figure to be in the same configuration as the adapting figure (ie positive bias); and neither introducing a delay period nor changing figure size had any effect. We conclude that these experiments reveal the distinct roles of transient, retinally localized neural processes as well as more stable, global processes under specifiable conditions.     

Children's understanding of ambiguous figures: Which cognitive developments are necessary to experience reversal?

In two experiments involving one hundred and thirty-eight 3- to 5-year-olds we examined the claim that a complex understanding of ambiguity is required to experience reversal of ambiguous stimuli [Gopnik, A., & Rosati, A. (2001). Duck or rabbit? Reversing ambiguous figures and understanding ambiguous representations. Developmental Science, 4, 175–183]. In Experiment 1 a novel Production task measured the ability to acknowledge both interpretations of ambiguous figures. This was as easy as and significantly correlated with a False Belief task, and easier than a Droodle task. We replicated this finding in Experiment 2, and also found that perceiving reversal of ambiguous figures was harder than either the False Belief or Production tasks. In contrast to previous findings, the Reversal and Droodle tasks were not specifically related. We conclude that children only attempt reversal once they can understand the representational relationship between the figure and its two interpretations. The process resulting in reversal however is hard, probably requiring additional developments in executive functioning and imagery abilities.     

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.     

The eyeglass reversal

Some figures, such as the Necker cube, are spontaneously reversible between alternative percepts. Before learning those skilled reversals, how do people achieve reversals for the very first time? It has been known that, in the case of a first reversal, peoplecan be expected to see the reversal when given specific information about how the figuresareambiguous. This point was confirmed by using drawing versions of reversible figures. To demonstrate how intention plays a role in the initial reversal of a real object, a pair of regular eyeglasses, reversible in perspective, were presented to naïve observers in monocular vision. When the eyeglasses were viewed inwardly and the observers were given information that the eyeglasses could be ambiguous, they were able to easily see the reversal. When the eyeglasses were viewed outwardly, observers saw it only after they had been informed of exactly what the two alternative percepts were.Interestingly, many observers often mistakenly saw the inwardly viewed eyeglasses as placed outwardly from the beginning of the observation, while they saw the outwardly viewed eyeglasses correctly. Taking these results together, for the first reversal of a real object, the specificity of intention varies with the ambiguity of the object.     

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.     

Further evidence of failure of reversal of ambiguous figures by uninformed subjects.

In studying the reversal of ambiguous figures investigators understandably have always informed subjects of the reversibility of the figures and of how each version appears. However, such knowledge may be a cause of reversal and is therefore an undesirable aspect of the method used to study it. An experiment is described that is an improvement in some respects on a previously reported one in which subjects are not informed about reversal. The result was that only about a third of the subjects ever reversed. In a control condition the same subjects were informed in the traditional way and then not only did they always reverse but did so very frequently in the time period tested. Theoretical implications of these findings are discussed.     

Stochastic properties of binocular rivalry alternations

Previous researches have demonstrated that the successive phase durations in binocular rivalry are independent. These findings are confirmed and extended to chromatic stimuli. The nature of the function that is shown to describe the distribution of the dominance phase durations is consistent with the independence of successive phases and suggests that a parallel may exist between binocular rivalry and the perceptual reversal of ambiguous figures.

     

Multidimensional shape similarity in the development of visual object classification

The current work examined age differences in the classification of novel object images that vary in continuous dimensions of structural shape. The structural dimensions employed are two that share a privileged status in the visual analysis and representation of objects: the shape of discrete prominent parts and the attachment positions of those parts. Experiment 1 involved a triad classification task in which participants at each of three different ages (5 years, 8 years, and adult) classified object images from two distinct stimulus sets. Across both sets, the youngest children demonstrated a systematic bias toward the shape of discrete parts during their judgments. With increasing age, participants increasingly came to select both the shape and the position of parts when classifying the images. The findings from Experiment 2 indicate that the local shape bias observed in young children's classifications is not merely a consequence of a discrimination advantage for that dimension. Results are discussed in relation to corresponding age-related changes in other functional contexts of visual processing.     

Reversing how to think about ambiguous figure reversals: spontaneous alternating by uninformed observers

Ambiguous figures are a special class of images that can give rise to multiple interpretations. Traditionally, switching between the possible interpretations of an ambiguous figure, or reversing one's interpretation, has been attributed either to top-down or to bottom-up processes (e.g. attributed to having knowledge of the nature of the ambiguity, or to a form of neuronal fatigue). Here we present evidence that is incompatible with both forms of explanations. Observers aged 5-9 years can reverse ambiguous figures when uninformed about the ambiguity, negating purely top-down explanations. Further, those children who make these 'spontaneous' reversals are more likely to succeed on a high-order theory-of-mind task, negating purely bottom-up explanations.     

The role of shape recognition in figure/ground perception in infancy

In this study we sought to determine whether infants, like adults, utilize previous experience to guide figure/ground processing. After familiarization to a shape, 5-month-olds preferentially attended to the side of an ambiguous figure/ground test stimulus corresponding to that shape, suggesting that they were viewing that portion as the figure. Infants’ failure to exhibit this preference in a control condition in which both sides of the test stimulus were displayed as figures indicated that the results in the experimental condition were not due to a preference between two figure shapes. These findings demonstrate for the first time that figure/ground processing in infancy is sensitive to top-down influence. Thus, a critical aspect of figure/ground processing is functional early in life.     

On what is bound in figures and grounds

All else being equal, regions providing a quick, good match to object memories are likely to be seen as shaped figures rather than as shapeless grounds. Good matches to object memories occur only if the parts are properly bound spatially. If object memories are accessed in the course of perceptual organization even for regions ultimately seen as shapeless grounds, then binding of parts cannot require attention to figures. Novel silhouette primes were shown immediately before real or novel line drawings. The silhouette contours of half of the primes preceding real line drawings sketched a known shape on the outside, which nevertheless appeared to be a shapeless ground. At short prime-line drawing SOAs, observers took longer to categorize real line drawings following these experimental primes than control primes, suggesting that parts are properly bound spatially for regions perceived to be shapeless grounds, and further that object memories matching grounds are inhibited.     

The perceived structural shape of thin (wire-like) objects is different from that of silhouettes

Observers are faster at judging the position of convex vertices compared to concave vertices. This is believed to be due to an explicit representation of position for visual parts. The best evidence comes from comparing the same contours perceived as either figures or holes, because this is a pure figure ground reversal (Bertamini and Croucher, 2003 Cognition 87 33 - 54; Bertamini and Mosca, 2004 Perception 33 35-48). Specifically, an interaction is present between type of object (object or hole) and shape. One assumption is that the contour of a silhouette is perceived as the rim of a solid object. It follows that a different pattern should be found for thin (wire-like) objects compared to silhouettes. We confirm this difference in three experiments. We argue that this is due to the perceived parts when contours can be interpreted as self-occlusion rims.     

Duck or rabbit? Reversing ambiguous figures and understanding ambiguous representations

In two studies we investigated 3‐ to 5‐year‐old children’s ability to reverse ambiguous figures and the relation between this ability and the ability to understand multiple representations. Children never reversed before they were informed of the two alternative interpretations of the figures. Even when they were informed of the alternatives and understood that both were possible, 3‐year‐olds and most 4‐year‐olds did not reverse. In contrast, a majority of 5‐year‐olds did reverse. In general, children only reversed if they also passed a standard false belief task. However, there was a closer correlation between reversals and a ‘droodle’ task that involved an understanding of the ambiguity of perceptual representations. These results suggest that the immediate experience of reversal may depend on a more abstract understanding of ambiguous representations.     

Inhibition Accompanies Reference-Frame Selection

Spatial relational terms are ambiguous because they can be defined by different and sometimes conflicting frames of reference. Previous research has suggested that multiple reference frames are simultaneously active before a reference frame is selected. Two experiments examined the on-line selection of a reference frame to determine whether it is assisted by inhibition. These experiments used a negative-priming paradigm in which access to a reference frame was assessed on trial n when that reference frame was either available but not selected or not available on trial n – 1. Significant negative priming was observed; it operated along the axis of the reference frame, encompassing both endpoints. In addition, reference-frame selection seems to be independent of object selection. We cast these findings within the view of negative priming as an inhibitory mechanism, and discuss their implications for the use of spatial relations.     

Comparisons between 25 reversible and ambiguous figures on measures of latency,duration, and fluctuation

Data are presented for 16 reversible and 9 ambiguous figures on measures of latency and duration of the initial response and total number of fluctuations during a 30-sec interval by 42 Ss. Of particular interest are the magnitudes, correlations, and factor analysis of eight widely used figures (e.g., Necker cube). The methodological advantages, theoretical ambiguities, and further research possibilities of this information are discussed.     

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.     

Creativity and ease of ambiguous figural reversal

Two studies examined the relationships between self-rated and objectively measured creative ability and ease of perceiving alternative interpretations of the ambiguous Duck-Rabbit figure. The studies found empirical support for what has previously been a largely analogical connection between figural reversal and creativity, using both self-rated trait creativity and objectively scored creative productivity. We discuss the hypothesis that executive functioning is the likely common cognitive factor linking perception of ambiguous figures and creative ability.