The temporal locus of the categorical bias in spatial memories

Abstract

People often use the region of a target's location to make judgements about its exact position. Although there is general agreement that this category-based effect is due to a blending of the specific coding of a target's location and the categorical coding of its region, there is little agreement on when the blending occurs. The current paper examines whether the systematic bias is the result of combining separate undistorted mental representations at the time of retrieval or a result of using a category-distorted mental representation. Participants studied a dot within a circle and reproduced its location from memory after a short or long delay, and new categorical information was introduced during target retrieval. The results showed a larger increase over time in the biases caused by the new category introduced at retrieval than in the biases caused by the originally encoded category. The findings are consistent with retrieval models, providing evidence that category biasing processes operate at the time of memory retrieval.

Keywords:

• Category adjustment model
• Category bias
• Spatial memory

Acknowledgments

Partially supported by NSF Grant BCS 03-17681 to RFW. We thank Christina Rappin and Alison Fernandez for collecting the data.

Notes

¹These regions were chosen because they are most informative about the effects of the two categories and allow their effects to be measured separately.

²The category factor reflects the set of bins that are most influenced by the default category (Bins 1 and 4) or the new category (Bins 2 and 3).

³There was no difference in reaction times at the SD and LD (both Ms = 1.4 s), indicating that the delay effects did not result from participants taking longer to respond in the long delay condition.