Manipulation of voice onset time during dichotic listening

The manipulation of voice onset time (VOT) during dichotic listening has provided novel insights regarding brain function. To date, the most common design is the utilisation of four VOT conditions: short-long pairs (SL), where a CV syllable with a short VOT is presented to the left ear and a CV syllable with a long VOT is presented to the right ear as well as long-short (LS), short-short (SS) and long-long (LL) pairs. Rimol, Eichele, and Hugdahl (2006) first reported that in healthy adults SL pairs elicit the largest REA while, in fact, LS pairs elicit a significant left ear advantage (LEA). This VOT effect was replicated by Sandmann et al. (2007). A study of children aged 5-8years of age has shown a developmental trajectory whereby long VOTs gradually start to dominate over short VOTs when LS pairs are being presented under dichotic conditions (Westerhausen, Helland, Ofte, & Hugdahl, 2010). Two studies have investigated attentional modulation of the VOT effect in children and adults. The converging evidence from these studies shows that at around 9years of age children lack the adult-like cognitive flexibility required to exert top-down control over stimulus-driven bottom-up processes (Andersson, Llera, Rimol, & Hugdahl, 2008; Arciuli, Rankine, & Monaghan, 2010). Arciuli et al. further demonstrated that this kind of cognitive flexibility is a predictor of proficiency with complex tasks such as reading. A review of each of these studies, the possible mechanisms underlying the VOT effect and directions for future research are discussed.