Ensemble perception in depth: Correct size-distance rescaling of multiple objects before averaging
Previous studies have shown that people are good at rapidly estimating ensemble summary statistics, such as the mean size of multiple objects. In the present study, we tested whether these average estimates are based on “raw” retinal representations (proximal sizes) or on how items should appear based on context, such as the viewing distance (distal sizes). In our experiments, observers adjusted the mean size of multiple objects presented at various apparent distances through a stereoscope. In Experiment 1, all items were shifted in depth by the same amount while the adjustable probe stayed at the fixed middle position. We found that presenting ensembles in an apparently remote plane made observers overestimate the mean size, which is consistent with angular sizes being rescaled to distance. In Experiment 2, we presented individual sizes in different planes. While angular sizes and apparent distances were kept controlled across conditions, we only manipulated correlations between them. These manipulations affected the precision of size averaging in line with changes in the range of apparent rather than angular sizes. This pattern is possible only if the visual system rescales each individual size to its distance prior to averaging. Our finding demonstrates that ensemble summaries of basic features, such as size, can be based on quite elaborated representations of multiple objects. We also discuss important implications for size constancy. (PsycINFO Database Record (c) 2019 APA, all rights reserved)
While looking at multiple objects, observers are able to extract summary statistics of the set of these objects. At the same time, they still perceive individual items, rather than an abstract statistical feature of the whole set. Our study was aimed at investigating the way perception of an individual object is altered by the ensemble of surrounding objects under focused and distributed attention settings. Observers were presented with sets of 1 to 16 circles of different sizes and were subsequently asked to determine the size of a target circle using a two-alternative forced choice procedure. The target location was either pre-cued, resulting in attention focus on a particular item, or post-cued, resulting in the distribution of attention across the entire set. We found a strong effect of the context on the individual target size estimation under both focused and distributed attention settings. The effect was stronger in distributed attention condition. Observers tended to «compress» the size of the largest items in ensembles, and this effect was stronger under the distributed attention setting. We explain this effect by the mechanism of feature unification that increases object similarity and facilitates holistic perception of the ensemble. Unification is weaker under focused attention, which permits better processing of individual objects.
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.
Objects have a variety of different features that can be represented as probability distributions. Recent findings show that in addition to mean and variance, the visual system can also encode the shape of feature distributions for features like color or orientation. In an odd-one-out search task we investigated observers' ability to encode two feature distributions simultaneously. Our stimuli were defined by two distinct features (color and orientation) while only one was relevant to the search task. We investigated whether the irrelevant feature distribution influences learning of the task-relevant distribution and whether observers also encode the irrelevant distribution. Although considerable learning of feature distributions occurred, especially for color, our results also suggest that adding a second irrelevant feature distribution negatively affected the encoding of the relevant one and that little learning of the irrelevant distribution occurred. There was also an asymmetry between the two different features: Searching for the oddly oriented target was more difficult than searching for the oddly colored target, which was reflected in worse learning of the color distribution. Overall, the results demonstrate that it is possible to encode information about two feature distributions simultaneously but also reveal considerable limits to this encoding.
Feature binding is an essential aspect of sensory processing. Neurophysiological mechanisms of this phenomenon are still under debate. Two experiments were conducted – in the auditory and visual modalities. We found than mismatch negativity in response to feature conjunctions was evident only in conditions of attention. Thus, we obtained the first electroencephalographic demonstration that feature binding depends upon attention.
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.
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.