Ensemble-based segmentation in the perception of multiple feature conjunctions
Although objects around us vary in a number of continuous dimensions (color, size, orientation, etc.), we tend to perceive the objects using more discrete, categorical descriptions (e.g., berries and leaves). Previously, we described howcontinuous ensemblestatistics ofsimple featuresaretransformedinto categorical classes: Thevisual system tests whether the feature distribution has one or several peaks, each representing a likely “category”. Here, we tested the mechanism of segmentation for more complex conjunctions of features. Observers discriminated between two textures ﬁlled with lines of various lengths and orientations, which had same distributions between the textures, but opposite directions of correlations. Critically, feature distributions could be “segmentable” (only extreme feature values and a large gap between them) or “non-segmentable” (both extreme and middle values with smooth transition are present). Segmentable displays yielded steeper psychometric functions indicating better discrimination (Experiment 1). The eﬀect of segmentability arises early in visual processing (Experiment 2) and is likely to be provided by global sampling of the entire ﬁeld (Experiment 3). Also, rapid segmentation requires both feature dimensions having a “segmentable” distribution supporting division of the textures into categorical classes of conjunctions. We propose that observers select items from one side (peak) of one dimension and sample mean diﬀerences along a second dimension within the selected subset. In this scenario, subset selection is alimiting factor (Experiment 4) oftexture discrimination. Yet, segmentability provided by the sharp feature distributions seems to facilitate both subset selection and mean comparison.
The heterogeneity of our visual environment typically reduces the speed with which a singleton target can be found. Visual search theories explain this via nontarget similarities and dissimilarities that affect grouping, perceptual noise, etc. Here, we show that increasing the heterogeneity of a display can facilitate rather than inhibit visual search for size and orientation singletons when heterogeneous features smoothly fill the transition between highly distinguishable nontargets. We suggest that this smooth transition reduce the “segmentability” of dissimilar items to otherwise separate subsets making the visual system to treat them as a near-homogenous sets opposing to a singleton.
Ensemble summary statistics represent multiple objects on the high level of abstraction—that is, without representing individual features and ignoring spatial organization. This makes them especially useful for the rapid visual categorization of multiple objects of different types that are intermixed in space. Rapid categorization implies our ability to judge at one brief glance whether all visible objects represent different types or just variants of one type. A framework presented here states that processes resembling statistical tests can underlie that categorization. At an early stage (primary categorization), when independent ensemble properties are distributed along a single sensory dimension, the shape of that distribution is tested in order to establish whether all features can be represented by a single or multiple peaks. When primary categories are separated, the visual system either reiterates the shape test to recognize subcategories (indepth processing) or implements mean comparison tests to match several primary categories along a new dimension. Rapid categorization is not free from processing limitations; the role of selective attention in categorization is discussed in light of these limitations.
This article describes the expierence of studying factors influencing the social well-being of educational migrants as mesured by means of a psychological well-being scale (A. Perrudet-Badoux, G.A. Mendelsohn, J.Chiche, 1988) previously adapted for Russian by M.V. Sokolova. A statistical analysis of the scale's reliability is performed. Trends in dynamics of subjective well-being are indentified on the basis the correlations analysis between the condbtbions of adaptation and its success rate, and potential mechanisms for developing subjective well-being among student migrants living in student hostels are described. Particular attention is paid to commuting as a factor of adaptation.
The distractive effects on attentional task performance in different paradigms are analyzed in this paper. I demonstrate how distractors may negatively affect (interference effect), positively (redundancy effect) or neutrally (null effect). Distractor effects described in literature are classified in accordance with their hypothetical source. The general rule of the theory is also introduced. It contains the formal prediction of the particular distractor effect, based on entropy and redundancy measures from the mathematical theory of communication (Shannon, 1948). Single- vs dual-process frameworks are considered for hypothetical mechanisms which underpin the distractor effects. Distractor profiles (DPs) are also introduced for the formalization and simple visualization of experimental data concerning the distractor effects. Typical shapes of DPs and their interpretations are discussed with examples from three frequently cited experiments. Finally, the paper introduces hierarchical hypothesis that states the level-fashion modulating interrelations between distractor effects of different classes.