Abstract: Even when stimuli are presented visually, the presence of irrelevant sound (IS) significantly impairs performance on immediate serial recall. Theoretical models provide conflicting accounts of the origins of irrelevant sound effects. The detailed pattern of interaction between IS and other factors influencing memory performance has been seen as placing important constraints on the development of models of short-term memory such as the working memory model and object-oriented episodic record model, but the fundamental question of the locus and mechanism of the IS effect has still not been satisfactorily resolved. To explore whether irrelevant sound has a significant influence on serial recall from short-term memory of Chinese characters, and to adjudicate between conflicting accounts, one experiment with varying levels of IS was conducted by 40 participants with Chinese characters. In the experiment, participants performed an arithmetic task follow the visually presence of Chinese characters list. This prevented them from memorizing the characters during the retention interval. The arithmetic task was three single digits drawn from 1 to 9. Participants were instructed to be as accurate as possible in calculating the sum of the digits. There were four IS conditions: in one condition participants heard no speech during the trial (no IS); in a second condition they heard three seconds of speech that started 50 ms before the visual presentation of the first item and ended 50ms before the onset of the first digit (IS during list); in a third condition participants heard three seconds of speech that started 50ms before the onset of the first digit and continued until 50 ms before the word "Recall'' (IS during sum); in the fourth condition, participants heard six seconds of speech that started 50 ms before the first item and continued until 50 ms before the recall cue (IS throughout). The four conditions were distributed equally and randomly around the 120 lists resulting in 30 lists per IS condition. The results were as follows: (1) Irrelevant sound had a retroactive effect on material in memory. Given the constraints placed on the participants by the requirement to perform the arithmetic task (correctly) during the retention interval, IS presented during a filled retention interval and IS throughout had a reliable effect on list recall. (2) Performance with no IS was not reliably better than that on the IS during list. (3) Serial position effects were observed in serial recall. Accuracy steadily declined towards the latter part of the list, but the performance of the last one was better than that of the former one. The results confirmed that a retroactive effect of IS persists even when we use an overt speeded digit-reading task to prevent rehearsal. The Object-oriented episodic record model for the irrelevant-speech effect needs to be reconsidered.

Key words: short-term memory, serial recall, irrelevant-sound effect, object-oriented episodic record model