Renewing the respect for similarity

In psychology, the concept of similarity has traditionally evoked a mixture of respect, stemming from its ubiquity and intuitive appeal, and concern, due to its dependence on the framing of the problem at hand and on its context. We argue for a renewed focus on similarity as an explanatory concept, by surveying established results and new developments in the theory and methods of similarity-preserving associative lookup and dimensionality reduction—critical components of many cognitive functions, as well as of intelligent data management in computer vision. We focus in particular on the growing family of algorithms that support associative memory by performing hashing that respects local similarity, and on the uses of similarity in representing structured objects and scenes. Insofar as these similarity-based ideas and methods are useful in cognitive modeling and in AI applications, they should be included in the core conceptual toolkit of computational neuroscience. In support of this stance, the present paper (1) offers a discussion of conceptual, mathematical, computational, and empirical aspects of similarity, as applied to the problems of visual object and scene representation, recognition, and interpretation, (2) mentions some key computational problems arising in attempts to put similarity to use, along with their possible solutions, (3) briefly states a previously developed similarity-based framework for visual object representation, the Chorus of Prototypes, along with the empirical support it enjoys, (4) presents new mathematical insights into the effectiveness of this framework, derived from its relationship to locality-sensitive hashing (LSH) and to concomitant statistics, (5) introduces a new model, the Chorus of Relational Descriptors (ChoRD), that extends this framework to scene representation and interpretation, (6) describes its implementation and testing, and finally (7) suggests possible directions in which the present research program can be extended in the future

Ventral-stream-like shape representation : from pixel intensity values to trainable object-selective COSFIRE models

Keywords: hierarchical representation, object recognition, shape, ventral stream, vision and scene understanding, robotics, handwriting analysisThe remarkable abilities of the primate visual system have inspired the construction of computational models of some visual neurons. We propose a trainable hierarchical object recognition model, which we call S-COSFIRE (S stands for Shape and COSFIRE stands for Combination Of Shifted FIlter REsponses) and use it to localize and recognize objects of interests embedded in complex scenes. It is inspired by the visual processing in the ventral stream (V1/V2 → V4 → TEO). Recognition and localization of objects embedded in complex scenes is important for many computer vision applications. Most existing methods require prior segmentation of the objects from the background which on its turn requires recognition. An S-COSFIRE filter is automatically configured to be selective for an arrangement of contour-based features that belong to a prototype shape specified by an example. The configuration comprises selecting relevant vertex detectors and determining certain blur and shift parameters. The response is computed as the weighted geometric mean of the blurred and shifted responses of the selected vertex detectors. S-COSFIRE filters share similar properties with some neurons in inferotemporal cortex, which provided inspiration for this work. We demonstrate the effectiveness of S-COSFIRE filters in two applications: letter and keyword spotting in handwritten manuscripts and object spotting in complex scenes for the computer vision system of a domestic robot. S-COSFIRE filters are effective to recognize and localize (deformable) objects in images of complex scenes without requiring prior segmentation. They are versatile trainable shape detectors, conceptually simple and easy to implement. The presented hierarchical shape representation contributes to a better understanding of the brain and to more robust computer vision algorithms.peer-reviewe

Zmiany w percepcji architektury i sztuki wobec działań awangardy

The Change in the Perception of Art and Architecture as a Result of Avant-garde MovementThe paper’s aim is to draw attention to perception of art and architecture in history. The quoted publications show the biological evolution and social development as the cause of change in the „visual awareness”. Th e most important stages in the development of artistic activity in the past and now highlight a departure from the classical notion of art and architectural object. Consequently, besides vision, other senses had to be involved in reading space. Selected examples of buildings represent an innovative approach of their authors, who try to aff ect the senses of the recipient in various ways. Th e paper also refers to the issue of creating descriptive models of perception for architecture, regarding the changes occurring in the latter

Evidence for holistic representations of ignored images and analytic representations of attended images

According to the hybrid theory of object recognition (Hummel, 2001), ignored object images are represented holistically, and attended images both holistically and analytically. This account correctly predicts patterns of visual priming as a function of translation, scale (Stankiewicz & Hummel, 2000) and left-right reflection (Stankiewicz, Hummel & Cooper, 1998). The model also predicts that priming for attended images will generalize over configural distortions (split images) whereas priming for ignored images will not. Three experiments tested and confirmed this prediction. Split images visually primed their intact and split counterparts when they were attended but not when they were ignored, whereas intact images primed themselves whether they were attended or not. The data contribute to the growing body of evidence that one function of visual attention is to permit the generation of explicitly relational representations of object shape

Shared features and similarity : implications for category specificity and normal recognition

Patients with category-specific visual agnosia (CSVA) often exhibit a disproportionate difficulty recognizing objects from biological categories due (in part) to the fact that exemplars from biological categories tend to be visually and conceptually more similar. Similarity is often conceived of as a pairwise property (i.e., in terms of distance in a psychological space matrix), but may be more accurately conceived of as a setwise property (i.e., in terms of shared features). The purpose of this study is to examine the effect of shared features on similarity in normal observers, while controlling for distance in structural space. Behavioral and electrophysiological results are presented that indicate that feature integration is necessary across a variety of tasks and that setwise properties (i.e., shared features) influence similarity. As such, it is suggested that future studies conceptualize similarity in terms of setwise (and not pairwise) object properties

Event-Related Potential Effects of Object Recognition depend on Attention and Part-Whole Configuration

The effects of spatial attention and part-whole configuration on recognition of repeated objects were investigated with behavioral and event-related potential (ERP) measures. Short-term repetition effects were measured for probe objects as a function of whether a preceding prime object was shown as an intact image or coarsely scrambled (split into two halves) and whether or not it had been attended during the prime display. In line with previous behavioral experiments, priming effects were observed from both intact and split primes for attended objects, but only from intact (repeated sameview) objects when they were unattended. These behavioral results were reflected in ERP waveforms at occipital–temporal locations as more negative-going deflections for repeated items in the time window between 220 and 300 ms after probe onset (N250r).Attended intact images showed generally more enhanced repetition effects than split ones. Unattended images showed repetition effects only when presented in an intact configuration, and this finding was limited to the right-hemisphere electrodes. Repetition effects in earlier (before 200 ms) time windows were limited to attended conditions at occipito-temporal sites during the N1, a component linked to the encoding of object structure, while repetition effects at central locations during the same time window (P150) were found for attended and unattended probes but only when repeated in the same intact configuration. The data indicate that view-generalization is mediated by a combination of analytic (part-based) representations and automatic view-dependent representations

Object representations in ventral and dorsal visual streams: fMRI repetition effects depend on attention and part–whole configuration

The effects of attention and object configuration on the neural responses to short-lag visual image repetition were investigated with fMRI. Attention to one of two object images in a prime display was cued spatially. The images were either intact or split vertically; a manipulation that negates the influence of view-based representations. A subsequent single intact probe image was named covertly. Behavioural priming observed as faster button presses was found for attended primes in both intact and split configurations, but only for uncued primes in the intact configuration. In a voxel-wise analysis, fMRI repetition suppression (RS) was observed in a left mid-fusiform region for attended primes, both intact and split, whilst a right intraparietal region showed repetition enhancement (RE) for intact primes, regardless of attention. In a factorial analysis across regions of interest (ROIs) defined from independent localiser contrasts, RS for attended objects in the ventral stream was significantly left-lateralised, whilst repetition effects in ventral and dorsal ROIs correlated with the amount of priming in specific conditions. These fMRI results extend hybrid theories of object recognition, implicating left ventral stream regions in analytic processing (requiring attention), consistent with prior hypotheses about hemispheric specialisation, and implicating dorsal stream regions in holistic processing (independent of attention)