Hemispheric asymmetries in auditory distraction Patrik Sörqvist a, * , John E. Marsh b , Helena Jahncke a a Department of Building, Energy and Environmental Engineering, University of Gävle, Gävle, Sweden b School of Psychology, Cardiff University, Cardiff, UK article info Article history: Accepted 30 June 2010 Available online 4 August 2010 Keywords: Right ear disadvantage Left ear disadvantage Semantic auditory distraction Hemispheric asymmetries abstract Serial-verbal short-term memory is impaired by irrelevant sound, particularly when the sound changes acoustically (the changing-state effect). In contrast, short-term recall of semantic information is impaired only by the semanticity of irrelevant speech, particularly when it is semantically related to the target memory items (the between-sequence semantic similarity effect). Previous research indicates that the changing-state effect is larger when the sound is presented to the left ear in comparison to the right ear, the left ear disadvantage. In this paper, we report a novel finding whereby the between-sequence semantic similarity effect is larger when the irrelevant speech is presented to the right ear in comparison to the left ear, but this right ear disadvantage is found only when meaning is the basis of recall (Experi- ments 1 and 3), not when order is the basis of recall (Experiment 2). Our results complement previous research on hemispheric asymmetry effects in cross-modal auditory distraction by demonstrating a role for the left hemisphere in semantic auditory distraction. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction Evolution has shaped the brain’s hemispheres into two func- tionally specialised processing systems (Kinsbourne, 1970). One source of evidence for hemispheric specialisation comes from the demonstration of a number of deficits (and syndromes) associated with the language functions of brain-damaged patients (Searl- eman, 1977). Another source of evidence for hemispheric speciali- sation comes from the finding that the auditory system has stronger contralateral than ipsilateral pathways that results in sound such as speech being processed predominantly by the oppo- site hemisphere to its presentation source. For example, input to the right ear has privileged access to the left hemisphere which plays a dominant role in the processing of linguistic information, and input to the left ear has privileged access to the right hemi- sphere which plays a more subservient role in linguistic processing and a more dominant role in non-linguistic processing (such as the processing of changes in complex auditory patterns; Shankweiler, 1966; Tzourio, Crivello, Mellet, Nkanga-Ngila, & Mazoyer, 1998). This is thought to result in the right ear advantage found in studies of linguistic sound processing and the left ear advantage found in studies of non-linguistic sound processing (Hugdahl et al., 2009; Poeppel et al., 2004; Tervaniemi & Hugdahl, 2003). These ear advantages have been demonstrated for to-be-attended sound. In the present article, we explore hemispheric asymmetry in the pro- cessing of to-be-ignored sound in a visual–verbal task setting (i.e., cross-modal auditory distraction). 1.1. The changing-state effect and right hemisphere processing Short-term verbal memory for the correct serial order of a set of sequentially presented visual items (visual–verbal serial recall) is markedly impaired by the mere presence of background sound that participants are explicitly instructed to ignore. Two key signatures of this irrelevant sound effect are that the to-be-ignored sound must change acoustically from one sound element to the next (Jones & Macken, 1993) and that the focal task must require serial rehearsal (seriation) of the to-be-recalled (TBR) items (Beaman & Jones, 1997; Hughes, Vachon, & Jones, 2007). If the participants are re- quired to recall the items in serial order, changing-state sound se- quences (e.g., ‘‘a b a b a b a”) are invariably more disruptive than steady-state sound sequences (e.g., ‘‘a a a a a a a”). This is called the changing-state effect. While the acoustic properties of the sound are endowed with disruptive power in the visual–verbal serial re- call setting, the meaning of the sound is relatively impotent (Buch- ner, Irmen, & Erdfelder, 1996; Jones & Macken, 1993; Tremblay, Nicholls, Alford, & Jones, 2000; but see Buchner, Rothermund, Wentura, & Mehl, 2004). These observations are in line with the view that the changing-state effect is a function of the similarity between two sets of order processes: The deliberate processing of the order of the TBR items and the involuntary processing of the order between successive and perceptually discrete sound events (for a review, see Macken, Tremblay, Alford, & Jones, 1999). 0278-2626/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.bandc.2010.06.007 * Corresponding author. Address: Department of Building, Energy and Environ- mental Engineering, University of Gävle, SE-801 76 Gävle, Sweden. E-mail address: patrik.sorqvist@hig.se (P. Sörqvist). Brain and Cognition 74 (2010) 79–87 Contents lists available at ScienceDirect Brain and Cognition journal homepage: www.elsevier.com/locate/b&c