http://www.journalofvision.org/content/10/12/27.abstract

What are the units of storage in visual working memory?

1. Daryl Fougnie
2. Christopher L. Asplund
3. René Marois

Abstract

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. Vogel, 1997).
Using a paradigm that independently estimates the number and precision of
items stored in working memory (W. Zhang & S. J. Luck, 2008), here we show
that the storage of features is not cost-free. The precision and number of
objects held in working memory was estimated when observers had to
remember either the color, the orientation, or both the color and
orientation of simple objects. We found that while the quantity of stored
objects was largely unaffected by increasing the number of features, the
precision of these representations dramatically decreased. Moreover, this
selective deterioration in object precision depended on the multiple
features being contained within the same objects. Such fidelity costs were
even observed with change detection paradigms when those paradigms placed
demands on the precision of the stored visual representations. Taken
together, these findings not only demonstrate that the maintenance of
integrated features is costly; they also suggest that objects and features
affect visual working memory capacity differently.

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Suggested reading by Ervin