Life-span development of visual working memory: when is feature binding difficult?

Abstract

We asked whether the ability to keep in working memory the binding between a visual object and its spatial location changes with development across the life span more than memory for item information. Paired arrays of colored squares were identical or differed in the color of one square, and in the latter case, the changed color was unique on that trial (item change) or was duplicated elsewhere in the array (color-location binding change). Children (8-10 and 11-12 years old) and older adults (65-85 years old) showed deficits relative to young adults. These were only partly simulated by dividing attention in young adults. The older adults had an additional deficiency, specifically in binding information, which was evident only when item- and binding-change trials were mixed together. In that situation, the older adults often overlooked the more subtle, binding-type changes. Some working memory processes related to binding undergo life-span development in an inverted-U shape, whereas other, bias- and salience-related processes that influence the use of binding information seem to develop monotonically.

Figure 1

An illustration of two types of stimulus change. Patterns represent colors. In item changes, a new color appears in the test array in the encircled location whereas, in binding changes, the color that appears in the encircled location matches a color already present elsewhere in the array. The drawing is not to scale.

Figure 2

An illustration of the effect of criterion bias on performance in a situation with item-change, binding-change, and no-change trials mixed together. Top panel: a conservative bias allows detection of most item changes and few binding changes. Bottom panel: a liberal bias allows detection of most item changes and also most binding changes. See text for details.

Figure 3

Proportions correct for every age group and change condition in Experiment 1a (which involved mixed trial blocks including item and binding trials), collapsed across set size. Error bars are standard errors.

Figure 4

Proportions correct for every age group, change condition, and array set size in Experiment 1a.

Figure 5

Proportions correct for the full and divided attention conditions in Experiment 1b. Standard errors for individual means in the figure were always below 0.08 for the full-attention condition and 0.10 for the divided-attention condition.

Figure 6

Proportions correct for every age group and change condition in Experiment 2a (which involved separate trial blocks for item and binding trials), collapsed across set size. Error bars are standard errors.

Figure 7

Proportions correct for every age group and condition in Experiment 2a (which involved separate trial blocks for item and binding trials).

Figure 8

Proportions correct for the full and divided attention conditions in Experiment 2b. Standard errors for individual means in the figure were always below 0.05.