Spatial clustering and hierarchical coding in immediate serial recall

Abstract

Four experiments are reported that demonstrate the benefits of clustering by spatial proximity in spatial serial recall and provide support for the notion that hierarchical coding underpins the retention of clustered sequences in spatial working memory. Sequences segregated by spatial clusters increased serial recall performance at different levels of sequence length in a variation of the Corsi test and produced a faster initial response time (RT), which indicates that they afforded data reducing processes. RT at cluster boundary increased in parallel with the number of items forming the clusters, suggesting that subroutines of different length were responsible for the ordering of items within clusters of different size. Evidence for hierarchical coding was also obtained in a serial recognition task, indicating this type of representation pertains to the retention of the sequences rather than exclusively to the organisation of the motor plan for the reproduction of the sequences.

Keywords:

• Chunking
• Serial recall
• Short-term memory
• Spatial memory
• Spatial organisation

Acknowledgements

This research was supported by Biotechnology and Biological Sciences Research Council (BBSRC) grant BB/C007840/1 to CDL. We are grateful to Tony Andrews for developing the software used in this study. We would also like to thank Clelia Rossi-Arnaud and an anonymous reviewer of a previous version of the manuscript whose comments greatly helped to improve this article.