Variability in the Quality of Visual Working Memory

Working memory is a mental storage system that keeps task-relevant information accessible for a brief span of time, and it is strikingly limited. Its limits differ substantially across people but are assumed to be fixed for a given person. Here we show that there is substantial variability in the quality of working memory representations within an individual. This variability can be explained neither by fluctuations in attention or arousal over time, nor by uneven distribution of a limited mental commodity. Variability of this sort is inconsistent with the assumptions of the standard cognitive models of working memory capacity, including both slot- and resource-based models, and so we propose a new framework for understanding the limitations of working memory: a stochastic process of degradation that plays out independently across memories.Psycholog

Object-Based Benefits without Object-Based Representations

The organization of visual information into objects strongly influences visual memory: Displays with objects defined by two features (e.g. color, orientation) are easier to remember than displays with twice as many objects defined by one feature (Olson & Jiang, 2002). Existing theories suggest that this ‘object-benefit’ is based on object-based limitations in working memory: because a limited number of objects can be stored, packaging features together so that fewer objects have to be remembered improves memory performance. This view predicts that memory for "packaged features" should be correlated (if you remember one feature of an object you should remember the object’s other features). Counter to this prediction, we show that some object features are stored largely independently. Participants were instructed to remember the colors and orientations of 5 colorful isosceles triangles (five-object condition) or the color of 5 colorful circles and the orientation of 5 black isosceles triangles (ten-object condition). After encoding (1200ms) and retention (900ms), memory was assessed with a continuous report for both features. Critically, participants reported both features of the same item in the five-object condition, allowing us to determine whether features were stored in an integrated fashion. Here we replicate the object-benefit: participants remembered twice as many features when arranged in 5 versus 10 objects. However, in the five-object condition memory for the color and orientation of an object was largely independent—when participants failed to accurately report the color or orientation of an object they were often quite accurate at judging the object's other feature. These results challenge the claim that the object-benefit is driven by the storage of integrated object representations, and require a revision of the concept of object-based memory representations. We propose that working memory is object-based in regard to the factors that enhance performance, but is feature-based at the level of representational failure.Psycholog

L’intégration géographique comme mode d’interprétation de l’évolution des stations balnéaires

La construction et l’évolution des stations balnéaires sont conditionnées par la perception que les différents acteurs du processus d’aménagement entretiennent avec la nature littorale. Depuis plus de 20 ans, cette relation semble s’être modifiée, au regard des pratiques «environnementalistes» ou relevant de la durabilité, prônant la mise en valeur de l’identité géographique du littoral. C’est en estimant et conceptualisant le degré d’intégration de cette nouvelle perception dans le processus d’aménagement qu’il est possible de décliner des modèles spatiaux originaux des stations environnementales, éco-touristiques et intégrées. Ce dernier cas se voulant l’interprétation optimale de la mutation contemporaine bouleversant la géographie des littoraux touristiques.The building and the evolution of the seaside resorts are conditionned by the perception of the nature of the coast which may differ among the different actors of the planning processe. During the last 20 years, this relation seems to have been changed, especialy when looking at the environmentalist or sustainable practices, which advocate the exploitation of the geographic identity of the coast. Assessing and conceptualizing the integration degree of this new perception in the planning process, we can present original spatial models of resorts, successively environnemental, ecotouristic and integrated. This last one is meant to be an optimal interpretation of the contemporary mutations that deeply change the geography of the touristic coast’

Training modulates memory-driven capture

Attention is captured by information matching the contents of working memory. Though many factors modulate the amount of capture, there is surprising resistance to cognitive control. Capture occurs even when participants are instructed either that an item would never be a target or to drop that item from memory. Does the persistence of capture under these conditions reflect a rigidity in capture, or can properly motivated participants learn to completely suppress distractors and/or completely drop items from memory? Surprisingly, no studies have looked at the influence of extensive training of involuntary capture from working memory items. Here, we addressed whether training leads to a reduction or even elimination of memory-driven capture. After memorizing a single object, participants were cued to remember or to forget this object. Subsequently, they were asked to execute a search task. To measure capture, we compared search performances in displays that did and did not contain a distractor matching the earlier memorized object. Participants completed multiple experimental sessions over four days. The results showed that attentional capture by to-be-remembered distractors was reduced, but not eliminated in subsequent sessions compared with the first session. Training did not impact capture by to-be-forgotten objects. The results suggest observable, but limited, cognitive control over memory-driven capture

Modeling Visual Working Memory with the MemToolbox

The MemToolbox is a collection of MATLAB functions for modeling visual working memory. In support of its goal to provide a full suite of data analysis tools, the toolbox includes implementations of popular models of visual working memory, real and simulated data sets, Bayesian and maximum likelihood estimation procedures for fitting models to data, visualizations of data and fit, validation routines, model comparison metrics, and experiment scripts. The MemToolbox is released under the permissive BSD license and is available at http://memtoolbox.org.Psycholog

Brewster-angle measurements of sea-surface reflectance using a high resolution spectroradiometer

This paper describes the design, construction and testing of a ship-borne spectroradiometer based on an imaging spectrograph and cooled CCD array with a wavelength range of 350-800 nm and 4 nm spectral sampling. The instrument had a minimum spectral acquisition time of 0.1 s, but in practice data were collected over periods of 10 s to allow averaging of wave effects. It was mounted on a ship's superstructure so that it viewed the sea surface from a height of several metres at the Brewster angle (53 degrees) through a linear polarizing filter. Comparison of sea-leaving spectra acquired with the polarizer oriented horizontally and vertically enabled estimation of the spectral composition of sky light reflected directly from the sea surface. A semi-empirical correction procedure was devised for retrieving water-leaving radiance spectra from these measurements while minimizing the influence of reflected sky light. Sea trials indicated that reflectance spectra obtained by this method were consistent with the results of radiance transfer modelling of case 2 waters with similar concentrations of chlorophyll and coloured dissolved organic matter. Surface reflectance signatures measured at three locations containing blooms of different phytoplankton species were easily discriminated and the instrument was sufficiently sensitive to detect solar-stimulated fluorescence from surface chlorophyll concentrations down to 1 mg m−3

What are the units of storage in visual working memory?

An influential theory suggests that integrated objects, rather than individual features, are the fundamental units that limit our capacity to temporarily store visual information (S. J. Luck & E. K

Modeling visual working memory with the MemToolbox

The MemToolbox is a collection of MATLAB functions for modeling visual working memory. In support of its goal to provide a full suite of data analysis tools, the toolbox includes implementations of popular models of visual working memory, real and simulated data sets, Bayesian and maximum likelihood estimation procedures for fitting models to data, visualizations of data and fit, validation routines, model comparison metrics, and experiment scripts. The MemToolbox is released under the permissive BSD license and is available at http:// memtoolbox.org

Environmental Snapshots from ACE-Asia

On five occasions spanning the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) field campaign in spring 2001, the Multiangle Imaging Spectroradiometer spaceborne instrument took data coincident with high-quality observations by instruments on two or more surface and airborne platforms. The cases capture a range of clean, polluted, and dusty aerosol conditions. With a three-stage optical modeling process, we synthesize the data from over 40 field instruments into layer-by-layer environmental snapshots that summarize what we know about the atmospheric and surface states at key locations during each event. We compare related measurements and discuss the implications of apparent discrepancies, at a level of detail appropriate for satellite retrieval algorithm and aerosol transport model validation. Aerosols within a few kilometers of the surface were composed primarily of pollution and Asian dust mixtures, as expected. Medium- and coarse-mode particle size distributions varied little among the events studied; however, column aerosol optical depth changed by more than a factor of 4, and the near-surface proportion of dust ranged between 25% and 50%. The amount of absorbing material in the submicron fraction was highest when near-surface winds crossed Beijing and the Korean Peninsula and was considerably lower for all other cases. Having simultaneous single-scattering albedo measurements at more than one wavelength would significantly reduce the remaining optical model uncertainties. The consistency of component particle microphysical properties among the five events, even in this relatively complex aerosol environment, suggests that global, satellite-derived maps of aerosol optical depth and aerosol mixture (air-mass-type) extent, combined with targeted in situ component microphysical property measurements, can provide a detailed global picture of aerosol behavior