Transformation Direction Influences Shape-Similarity Judgments

Similarity and structured representation in human and nonhuman apes

How we judge the similarity between objects in the world is connected ultimately to how we represent those objects. It has been argued extensively that object representations in humans are 'structured' in nature, meaning that both individual features and the relations between them can influence similarity. In contrast, popular models within comparative psychology assume that nonhuman species appreciate only surface-level, featural similarities. By applying psychological models of structural and featural similarity (from conjunctive feature models to Tversky's Contrast Model) to visual similarity judgements from adult humans, chimpanzees, and gorillas, we demonstrate a cross-species sensitivity to complex structural information, particularly for stimuli that combine colour and shape. These results shed new light on the representational complexity of nonhuman apes, and the fundamental limits of featural coding in explaining object representation and similarity, which emerge strikingly across both human and nonhuman species.

Opposites in Reasoning Processes: Do We Use Them More Than We Think, but Less Than We Could?

Our aim in this paper is to contribute toward acknowledging the general role of opposites as an organizing principle in the human mind. We support this claim in relation to human reasoning by collecting evidence from various studies which shows that "thinking in opposites" is not only involved in formal logical thinking, but can also be applied in both deductive and inductive reasoning, as well as in problem solving. We also describe the results of a series of studies which, although they have been developed within a number of different theoretical frameworks based on various methodologies, all demonstrate that giving hints or training reasoners to think in terms of opposites improves their performance in tasks in which spontaneous thinking may lead to classic biases and impasses. Since we all possess an intuitive idea of what opposites are, prompting people to "think in opposites" is something which is undoubtedly within everyone's reach and in the final section, we discuss the potential of this strategy and suggest possible future research directions of systematic testing the benefits that might arise from the use of this technique in contexts beyond those tested thus far. Ascertaining the conditions in which reasoners might benefit will also help in terms of clarifying the underlying mechanisms from the point of view, for instance, of analytical, conscious processing vs. automatic, unconscious processing.

The role of semantics in the perceptual organization of shape

Establishing correspondence between objects is fundamental for object constancy, similarity perception and identifying transformations. Previous studies measured point-to-point correspondence between objects before and after rigid and non-rigid shape transformations. However, we can also identify 'similar parts' on extremely different objects, such as butterflies and owls or lizards and whales. We measured point-to-point correspondence between such object pairs. In each trial, a dot was placed on the contour of one object, and participants had to place a dot on 'the corresponding location' of the other object. Responses show correspondence is established based on similarities between semantic parts (such as head, wings, or legs). We then measured correspondence between ambiguous objects with different labels (e.g., between 'duck' and 'rabbit' interpretations of the classic ambiguous figure). Despite identical geometries, correspondences were different across the interpretations, based on semantics (e.g., matching 'Head' to 'Head', 'Tail' to 'Tail'). We present a zero-parameter model based on labeled semantic part data (obtained from a different group of participants) that well explains our data and outperforms an alternative model based on contour curvature. This demonstrates how we establish correspondence between very different objects by evaluating similarity between semantic parts, combining perceptual organization and cognitive processes.

Getting "fumpered": Classifying objects by what has been done to them

Every object acquires its shape from some kind of generative process, such as manufacture, biological growth, or self-organization, in response to external forces. Inferring such generative processes from an observed shape is computationally challenging because a given process can lead to radically different shapes, and similar shapes can result from different generative processes. Here, we suggest that in some cases, generative processes endow objects with distinctive statistical features that observers can use to classify objects according to what has been done to them. We found that from the very first trials in an eight-alternative forced-choice classification task, observers were extremely good at classifying unfamiliar objects by the transformations that had shaped them. Further experiments show that the shape features underlying this ability are distinct from Euclidean shape similarity and that observers can separate and voluntarily respond to both aspects of objects. Our findings suggest that perceptual organization processes allow us to identify salient statistical shape features that are diagnostic of generative processes. By so doing, we can classify objects we have never seen before according to the processes that shaped them.

Visual perception of shape altered by inferred causal history

One of the main functions of vision is to represent object shape. Most theories of shape perception focus exclusively on geometrical computations (e.g., curvatures, symmetries, axis structure). Here, however, we find that shape representations are also profoundly influenced by an object’s causal origins: the processes in its past that formed it. Observers placed dots on objects to report their perceived symmetry axes. When objects appeared ‘complete’—created entirely by a single generative process—responses closely approximated the object’s geometrical axes. However, when objects appeared ‘bitten’—as if parts had been removed by a distinct causal process—the responses deviated significantly from the geometrical axes, as if the bitten regions were suppressed from the computation of symmetry. This suppression of bitten regions was also found when observers were not asked about symmetry axes but about the perceived front and back of objects. The findings suggest that visual shape representations are more sophisticated than previously appreciated. Objects are not only parsed according to what features they have, but also to how or why they have those features.

Familiarity, Priming, and Perception in Similarity Judgments

We present a novel way of accounting for similarity judgments. Our approach posits that similarity stems from three main sources-familiarity, priming, and inherent perceptual likeness. Here, we explore each of these constructs and demonstrate their individual and combined effectiveness in explaining similarity judgments. Using these three measures, our account of similarity explains ratings of simple, color-based perceptual stimuli that display asymmetry effects, as well as more complicated perceptual stimuli with structural properties; more traditional approaches to similarity solve one or the other and have difficulty accounting for both. Overall, our work demonstrates the importance of each of these components of similarity in explaining similarity judgments, both individually and together, and suggests important implications for other similarity approaches.

Visual perception of complex shape-transforming processes

Morphogenesis-or the origin of complex natural form-has long fascinated researchers from practically every branch of science. However, we know practically nothing about how we perceive and understand such processes. Here, we measured how observers visually infer shape-transforming processes. Participants viewed pairs of objects ('before' and 'after' a transformation) and identified points that corresponded across the transformation. This allowed us to map out in spatial detail how perceived shape and space were affected by the transformations. Participants' responses were strikingly accurate and mutually consistent for a wide range of non-rigid transformations including complex growth-like processes. A zero-free-parameter model based on matching and interpolating/extrapolating the positions of high-salience contour features predicts the data surprisingly well, suggesting observers infer spatial correspondences relative to key landmarks. Together, our findings reveal the operation of specific perceptual organization processes that make us remarkably adept at identifying correspondences across complex shape-transforming processes by using salient object features. We suggest that these abilities, which allow us to parse and interpret the causally significant features of shapes, are invaluable for many tasks that involve 'making sense' of shape.

Exploring the Psychological Structure of Transformational Knowledge in Visual and Haptic Intramodal Conditions Using Multidimensional Scaling

The intramodal relation between perceptual similarity and categorization performance in a psychological space, as indicated by multidimensional scaling (MDS) analysis of similarity judgments, was explored. Participants learned to classify transformed object shapes into three categories either visually or haptically via different training procedures (either random or systematic), followed by a transfer test. Learning modulated the psychological spaces, but this effect was more prevalent with haptic than with visual tasks. A prototype model for similarity ratings was illustrated in MDS space. The prototypes were multidimensionally scaled at the center of a category, rather than mirroring the bidirectional paths of their origins. Although they converged at the apex of two transformational trajectories, the category prototypes anchored at the centroid of their respective categories and became more structured as a function of learning. The reduced tendency to make errors (i.e., higher accuracy) in recognizing and classifying the category prototypes suggested that prototypical representation of a category abstracted from exemplar averaging functioned more as novel, rather than familiar, information. Findings were discussed in terms of transformational knowledge, categorical representation in three-dimensional (3D) space, and intramodal visual and haptic similarity.

Similarity-based asymmetries in perceptual matching

Asymmetries, where response times differ depending on the order of two stimuli, have been widely used to explore fundamental aspects of perceptual processing. Given how much is made of asymmetries in the study of perception there has been surprisingly little research into the cognitive mechanisms that may underlie why comparing two objects in isolation depends on the order of presentation. In visual search, for example, asymmetries are typically attributed to fundamental processing characteristics as opposed to the inherent relation between two stimuli. However, one possible explanation for asymmetries found in perceptual processing is that similarity is important in the task and it is similarity itself that is asymmetric. In the current paper, we use a stimulus set for which the transformational account of similarity predicts asymmetries based on differences in transformational complexity. Using the fine-grained measure of reaction time we show that directional differences in transformation distance successfully predict asymmetries in the speed of matching two stimuli in sequence. The results are discussed in relation to the role of transformations in perceptual identification more generally, and how transformations could be revealing about how objects are compared in other experimental contexts where objects are compared directionally (e.g., visual search).