Own-race faces are generally recognised more accurately than other-race faces (Meissner & Brigham, 2001). Two major theories attempt to explain the own-race bias (ORB) and similar own-group biases; social-cognitive and perceptual expertise theories. Perceptual theories expect that increased experience recognising own-race faces leads to a more effective processing style tuned to these faces (e.g., Stahl, Wiese & Schweinberger, 2008). Social-cognitive theories point to categorisation of other-group members at the expense of processing their individual identity, and greater motivation to attend to in-group members (Bernstein, Young & Hugenberg, 2007; Levin, 2001). Both of these theoretical accounts can be used to predict own-group biases in voice processing. An own-sex bias in voice processing was tested (experiment 2.1), and an own-accent bias was found in recognition memory (experiment 3.1). Contributions from perceptual expertise and social-cognitive mechanisms to this bias were then studied. By manipulating the supposed social power of speakers, support for the social-cognitive view was found (experiment 3.2). Event-related potentials (ERPs) revealed further support. This was because an own-accent bias was found in ERP measures of voice discrimination, but not in the ability to discriminate between voices (while ignoring them). Support for the social-cognitive view was limited when studying faces however. There was no evidence of own-group bias for physically. similar face groups (experiments 3.3,5.1 and 6.1). Evidence from eye-tracking found that attention was directed towards the most diagnostic face areas for individual recognition (experiment 5.2). Knowledge of diagnostic areas is best explained by perceptual expertise. Importantly however, unbiased participants adjusted their viewing behaviour according to the most diagnostic areas of each race. Finally, analysis of saccades revealed greater difficulty ignoring own-race faces (experiment 6.2), although there was no such bias for physically similar social groups (experiment 6.1). The implications of these findings and directions for future research are discussed.