Visual search for changes in scenes creates long-term, incidental memory traces
Humans are very good at remembering large numbers of scenes over substantial periods of time. How good are they at remembering changes to scenes? In this study, we tested scene memory and change detection two weeks after initial scene learning. In Experiments 1-3, scenes were learned incidentally during visual search for change. In Experiment 4, observers explicitly memorized scenes. At Test, after two weeks, observers were asked to discriminate old from new scenes, to recall a change that they had detected in the study phase, or to detect a newly introduced change in the memorization experiment. Next, they performed a change detection task, usually looking for the same change from the study period. Scene recognition memory was found to be similar in all experiments, regardless of study task. In Experiment 1, more difficult change detection produced better scene memory. Experiments 2 and 3 supported a ‘depth of processing’ account for the effects of initial search and change detection on incidental memory for scenes. Of most interest, change detection during the Test phase was faster than during the Study phase, even when the observer had no explicit memory of having found that change previously. This result was replicated in two of three change detection experiments. We conclude that scenes can be encoded incidentally as well as explicitly and that changes in those scenes can leave measurable traces even if they are not explicitly recalled.
The capacity of fine vision of individual object is limited by the "bottleneck" of attention and working memory. Still, at every moment we see large collections of objects. What exactly happens to individual representations when the observer attempts to distribute attention between multiple objects? One view is that a fixed number of objects are represented with good fidelity while others are represented with poor fidelity. Another theory is that attention is evenly distributed among all objects but fidelity decreases as set size grows. This debate is one in the core of a theory of summary representation of multiple objects (Alvarez, 2011; Myczek & Simons, 2008). Here we directly tested how the capacity and fidelity change with set size. Participants were briefly shown sets of 1, 2, 4, or 8 circles of various sizes. Then, one of the circles increased or decreased in size by 2- 20% (change step 2%). The change was synchronized with a global background flash masking the local transient caused by the circle change. Observers had to respond whether they had seen an increment or decrement in any of the circles (2AFC). These manipulations rely on an assumption that one needs attention to the stimulus to spot a change (Rensink et al., 1997). Psychometric functions were fit using normal cumulative density functions. We found that the set size affects the probability of correct response at which the function reaches a plateau: the larger was a set size, the lower was such probability. The standard deviations of the functions typically associated with fidelity were relatively similar across set sizes within each observer. We conclude, therefore, that, when observers perceive multiple objects during a short time, they focus attention on a limited sample of items represented with the same fidelity, rather than evenly distribute it among all the objects.
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.
Three experiments examined spatial allocation of attention during active search for visual changes. In all experiments, there were three conditions of change location related to a centre of interest: (1) Central (most attended location itself), (2) near, and (3) far marginal change. In Experiment 1, participants showed the slowest search and the largest number of undetected changes in near condition. Moreover, they misidentified near changes more frequently than central and far ones. In Experiment 2, participants had to search for marginal changes in the presence of a once noticed central change that summoned additional attention to a central location. It resulted in further search slowing for near changes. In Experiment 3, participants searched for one of two concurrent marginal changes in the presence of a central one. They detected far changes about 2.3 times more frequently than near ones. Taken together, these results support the notion of «dead zone of attention» surrounding attentional focus. Several speculations about the nature of dead zone are discussed.
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.