An isolation effect in serial memory for spatial information

Abstract

This paper reports the first demonstration of an isolation effect or von Restorff effect (von Restorff, 1933) in the context of a spatial-memory task: Short-term serial recall was enhanced for both the location and the serial position of one red dot presented amongst a sequence of otherwise black dots. When the serial position of the isolate was fixed, the spatial isolation effect only emerged when participants received a control block of trials before the block of isolation trials (Experiment 1). However, when the serial position of the isolate was varied across isolation trials, an isolation effect was still produced regardless of condition order (Experiment 2). It is suggested that both temporal grouping strategies and greater item-specific processing may have contributed to the enhanced retention of the isolate.

Acknowledgments

Thanks are due to Josée Bluteau for assistance in running the experiment. We would also like to thank François Vachon for critical reading of an earlier draft. This research was supported by operating grants from the Natural Sciences and Engineering Research Council of Canada to Sébastien Tremblay.

Notes

¹Other methods such as the city block procedure (e.g., Farrand & Jones, 1996) and the best-fit solution (e.g., Postma & de Haan, 1996) provide continuous measures—in relation to the distance between the response and the location—rather than a binary outcome. However, such measures make the distinction between item and order difficult. The increased sensitivity of these procedures is not necessary in the current study as the classical binary scoring method proved to be sensitive to a panoply of effects such as grouping (Parmentier et al., 2006) and interference (Tremblay, Nicholls, Parmentier, & Jones, 2005) and here, to the isolation effect for both item and order criteria.