Real-world objects are not stored in holistic representations in visual working memory
When storing multiple objects in visual working memory, observers sometimes misattribute perceived features to incorrect locations or objects. These misattributions are called binding errors (or swaps) and have been previously demonstrated mostly in simple objects whose features are easy to encode independently and arbitrarily chosen, like colors and orientations. Here, we tested whether similar swaps can occur with real-world objects, where the connection between features is meaningful rather than arbitrary. In Experiments 1 and 2, observers were simultaneously shown four items from two object categories. Within a category, the two exemplars could be presented in either the same or different states (e.g., open/closed; full/empty). After a delay, both exemplars from one of the categories were probed, and participants had to recognize which exemplar went with which state. We found good memory for state information and exemplar information on their own, but a significant memory decrement for exemplar–state combinations, suggesting that binding was difficult for observers and swap errors occurred even for meaningful real-world objects. In Experiment 3, we used the same task, but in one-half of the trials, the locations of the exemplars were swapped at test. We found that there are more errors in general when the locations of exemplars were swapped. We concluded that the internal features of real-world objects are not perfectly bound in working memory, and location updates impair object and feature representations. Overall, we provide evidence that even real-world objects are not stored in an entirely unitized format in working memory.
It was previously shown that the features of individual items retrieved from visual working memory (VWM) are systematically biased towards the mean feature of a sample set (Brady & Alvarez, 2011), suggesting hierarchical encoding in VWM. In our work, we investigated how hierarchical representations are stored over time. Observers were shown four differently oriented triangles for 200 ms and, after 1-, 4-, or 7-second delay, they had to report either one individual orientation, or the average orientation of all triangles, rotating a probe circle. Before set presentations, observers were informed that they had to remember one particular orientation, all four individual orientations, or the average orientation. Using the mixture model (Zhang & Luck, 2008), we estimated a probability of a tested representation being in VWM and its precision, as well as a systematic bias that would indicate hierarchical encoding. We found a strong bias towards the mean in the “remember four” condition, which provides evidence for hierarchical encoding in VWM. Our main result was the absence of significant changes in retaining the elements of a hierarchical representation (the mean and individual features). This supports an idea that hierarchical representations are related to encoding, rather than storing in VWM. Both fidelity and the probability of an item being in memory decrease over time. It supports "Sudden Death" and "Gradual Decay" accounts for storing hierarchical representations.
Previous research has documented the limited capacity of visual working memory (VWM) for color objects set at 3–5 items. Another line of research has shown that multiple objects can be stored in a compressed form of ensemble. However, existing data is more likely to testify that VWM can store no more than two such compressed units. But the nature of this discrepancy can be methodological: VWM for ensembles was never tested using methods that are applied in the research of VWM for objects. Here we have tested the capacity and precision of VWM for objects and ensembles using two standard methods — change detection and continuous report with a mixture model. We found that VWM for both types of units showed the similar capacity and precision when critical psychophysical parameters, such as foveal density and area are controlled. We also showed that this quantitative similarity between objects and ensembles is provided by a mechanism that represents each ensemble as a holistic VWM chunk as efficiently as it represents any single object.
Our interactions with the visual world are guided by attention and visual working memory. Things that we look for and those we ignore are stored as templates that reflect our goals and the tasks at hand. The nature of such templates has been widely debated. A recent proposal is that these templates can be thought of as probabilistic representations of task-relevant features. Crucially, such probabilistic templates should accurately reflect feature probabilities in the environment. Here we ask whether observers can quickly form a correct internal model of a complex (bimodal) distribution of distractor features. We assessed observers’ representations by measuring the slowing of visual search when target features unexpectedly match a distractor template. Distractor stimuli were heterogeneous, randomly drawn on each trial from a bimodal probability distribution. Using two targets on each trial, we tested whether observers encode the full distribution, only one peak of it, or the average of the two peaks. Search was slower when the two targets corresponded to the two modes of a previous distractor distribution than when one target was at one of the modes and another between them or outside the distribution range. Furthermore, targets on the modes were reported later than targets between the modes that, in turn, were reported later than targets outside this range. This shows that observers use a correct internal model, representing both distribution modes using templates based on the full probability distribution rather than just one peak or simple summary statistics. The findings further confirm that performance in odd-one out search with repeated distractors cannot be described by a simple decision rule. Our findings indicate that probabilistic visual working memory templates guiding attention, dynamically adapt to task requirements, accurately reflecting the probabilistic nature of the input.
This article reviews the research in visual working memory (VWM) over the past 20 years. We describe research methodologies in the field and focus on commonly used paradigms such as change detection and continuous report (including the use of mixed models for analysis) that aim to measure the capacity and precision of VWM. We also consider the organization of units of storage in VWM; in particular, we describe feature binding and representing multiple objects as ensemble summary statistics. We review theories that try to explain the nature of VWM limitations: structural theories (slot-based), resource theories, hybrid theories (slot and resource theories), and a recently suggested hierarchical encoding theory. Theories aiming to explain forgetting mechanisms in VWM are reviewed. We also discuss the neural correlates of VWM encoding and storage, as well as neurophysiological models of VWM that are substantially influenced by the mentioned theories.
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.