Ambiguous figures and representationalism

Ambiguous figures pose a problem for representationalists, particularly for representationalists who believe that the content of perceptual experience is non-conceptual (MacPherson in Nous 40(1):82–117, 2006). This is because, in viewing ambiguous figures, subjects have perceptual experiences that differ in phenomenal properties without differing in non-conceptual content. In this paper, I argue that ambiguous figures pose no problem for non-conceptual representationalists. I argue that aspect shifts do not presuppose or require the possession of sophisticated conceptual resources and that, although viewing ambiguous figures often causes a change in phenomenal properties, this change is accompanied by a change in non-conceptual content. I illustrate the case by considering specific examples.     

Ambiguous figures and representationalism

Macpherson (Nous 40(1):82–117, 2006) argues that the square/regular diamond figure threatens representationalism, construed as the theory which holds that the phenomenal character is explained by the nonconceptual content of experience. Her argument is the claim that representationalism is committed to the thesis that differences in the experience of ambiguous figures, the gestalt switch, should be explained by differences in the NCC of perception of these figures. However, with respect to the square/regular diamond and some other ambiguous figure representationalism fails to offer a unified account of how representational content makes them ambiguous. In this paper, I aim, first, to offer a representationalist account of ambiguous figures and, second, to examine and rebut Macpherson’s arguments. My main point is that in each ambiguous figure Macpherson discusses there are differences in representational content that can explain differences in phenomenal character or content. The representational differences are due to the ways the Cartesian frame of reference in which perceptual content is always cast cuts the figure, underlying different properties of the figure with respect to the axes of the Cartesian frame of reference.     

Ambiguous figures, attention, and perceptual content: reply to Jagnow

I argued in Nanay 2010 that we cannot characterize perceptual content without reference to attention. Here, I defend this account from three objections raised by Jagnow 2011. This mainly takes the form of clarifying some details not sufficiently elaborated in the original article and dispelling some potential misunderstandings.     

Ambiguous figures: living versus nonliving objects

Eleven series of figures were studied, each series ranging from one extreme interpretation via five ambiguous intermediates to a second extreme interpretation. Triplets consisting of an ambiguous exemplar in the middle flanked on the left and right by its two extreme interpretations were presented to large groups of subjects. The initial aim was to establish the levels of perceptual ambiguity of each exemplar in a series, and normative data on the ambiguous figures are provided for future reference and use. However, several biases were encountered and these were examined in more detail. In experiment 1 the subject's task was to compare the middle figure with the flankers and draw an arrow from the middle figure towards the flanking extreme they judged the most similar. Here, an overall preference for the left extreme was found. Therefore the instructions were reversed in experiment 2; flankers had to be compared with the middle figure. The preference for the left extreme remained for figures of living objects, but for nonliving objects the preference switched to the right extreme. To do away with any effect of the arrows, in experiment 3 subjects were divided into two groups each receiving different instructions and were asked to circle one of the extremes. However, the pattern of biases remained the same. The bias found with figures of living objects may be explained on the basis of top-down processes. For nonliving figures, an hypothesis based on bottom-up processes like neural fatigue was considered but rejected.     

Ambiguous musical figures and auditory streaming

Three experiments with musicians and nonmusicians (N=338) explored variations of Deutsch’s musical scale illusion. Conditions under which the illusion occurs were elucidated and data obtained which supported Bregman’s suggestion that auditory streaming results from a competition among alternative perceptual organizations. In nExperiment 1, a series of studies showed that it is more difficult to induce the scale illusion than might be expected if it is accepted that an illusion will be present for most observers despite minor changes in stimuli and experimental conditions, The stimulus sequence seems better described as an ambiguous figure. Having discovered conditions under which the scale illusion could be reliably induced, Experiments 2 and 3 manipulated additional properties of the stimulus (timbre, loudness, and tune) to provide cues to streaming other than pitch and location. The data showed that streaming of this sequence can be altered by these properties, supporting the notion of a general parsing mechanism which follows general gestalt principles and allows streaming by many stimulus dimensions. Finally, suggestions are made as to how this mechanism might operate.     

Ambiguous figures: role of context and critical features

Context and attention to critical features as factors in determining the perceptual organization of ambiguous figures were investigated in the present two studies. In the first study, a fixation point directed attention to a critical or to a neutral feature of an ambiguous figure. Placement of the fixation point on different features of an ambiguous figure did not affect the figure-ground organization of the figure, but it did influence the speed of the identification response. In the second study, presentation of an ambiguous figure was preceded by a biased figure or by features of the figure. Results indicated that the interpretation of the ambiguous figure was overwhelmingly influenced by the advanced presentation of a biased drawing but only slightly influenced by the advanced presentation of a critical feature. These findings support analysis-by-synthesis (Neisser, 1967) as an explanation of the perception of ambiguous figures over other contemporary attention theories.     

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.     

Late influences on perceptual grouping: illusory figures

Two experiments demonstrate that grouping can be strongly influenced by the presence of figures defined by illusory contours. Rectangular arrays were constructed in which a central column of figures could group either with those on one side, on the basis of perception of figures defined by illusory contours, or with those on the other side, on the basis of physically present inducing elements. In all displays, subjects grouped according to the illusory figures significantly more often than for control displays that contained the same inducing elements, but rearranged so that illusory contours were degraded or eliminated. A second experiment showed that in objectively defined grouping tasks, subjects grouped faster by illusory figures than by inducing elements. These results indicate that grouping can occur after illusory contours have been perceived.     

Autism and the experience of a perceptual object

Sewards and Sewards (2002) argue that while computations necessary for object recognition occur throughout the ventral visual stream, object recognition awareness involves the anterior temporal lobe and the medial orbital prefrontal cortex. The present paper suggests, however, that the medial orbital prefrontal cortex has a unique contribution, namely that of producing a basic experience of a perceptual object. It is further argued that the mechanisms that produce this experience also result in making the object more important than its subparts and features. Finally, it is argued that a reduction in this importance may account for some perceptual difficulties in high-functioning autism. This view is consistent with evidence for early selective abnormalities in other systems involving the medial prefrontal cortex in autism.