Age-related associative deficits and the isolation effect

ABSTRACT

If all but one of the items in a list are similar (e.g., all black except one red), memory for the different item is enhanced (the isolation effect). Older adults generally show similar or smaller isolation effects compared to young adults, which has been attributed to age-related deficits in associative memory whereby older adults are less able to associate an isolated stimulus to its isolating feature. Experiment 1 examined the isolation effect for isolation based on spatial position, modality and color; in Experiment 2, the criterion for isolation was the associative relation between stimuli. The results consistently showed no differences between young and older participants in the magnitude of the isolation effect. Whilst age deficits in associative memory may act to reduce the isolation effect in older adults, age deficits in self-initiated processing and inhibitory functionality may counteract this reduction by enhancing the isolation effect in older adults.

Keywords:

• Aging
• Isolation effect
• Associative deficits
• Inhibition
• Memory

Acknowledgments

This study formed part of a doctoral dissertation by Stephen P. Badham funded by a University of Warwick Postgraduate Research Fellowship. The research was also supported by a grant from the Warwick Institute of Advanced Study. We are grateful to Lauren Brawn and Charlotte Gillingham for collecting the data for Experiment 2.

Notes

¹ Experimental details were acquired from a review by Hunt (1995) as the original paper was never printed in English.

² Given the relatively large age range of older adults, correlations were carried out between age and the magnitude of the isolation effect for older adults only. There was no significant correlation for modality or color, r(30) = –.281 and –.112, respectively, both p values > .1, but there was a significant correlation for spatial position, r(30) = –.460, p = .011, suggesting a reduced isolation effect with increasing age. Note, however, that spatial position was the isolating factor that showed the weakest isolation effect in both age groups; where isolation effects were significant (modality and color), there was no statistical support for a reduction with age within the older adult group.

Figure 3 Mean proportion of words recalled as a function of serial position for control and color isolation lists in Experiment 1.

Figure 1 Mean proportion of words recalled as a function of serial position for control and spatial position isolation lists in Experiment 1.

³ Note also that the modality isolate was recalled significantly earlier during output than the equivalent item in the other conditions and this was the case for young and older adults alike.

⁴ The same cannot be said for position isolation as no studies were found where spatial position of stimuli was an isolating factor.

⁵ These isolation effects were calculated by taking the difference between position 3 and positions 1, 2, 4, and 5 (averaged together) for both the control and isolation conditions and subtracting the former from the latter.