 Much of the leading research on implicit attitude measures has concerned racism, in accord with the view that racist attitudes, though common, are considered socially undesirable and therefore often not self-ascribed even when present. For example, Campbell, Kruskal, and Wallace (1966) explored the use of seating distance as an index of racial attitudes, noting that racially Black and White students tended to aggregate in classroom seating arrangements. Using facial electromyography (EMG), Vanman et al. (1997) found (racially) White participants to display facial responses indicative of negative affect more frequently when asked to imagine co-operative activity with Black than with White partners—results interpreted as indicative of racist attitudes. Cunningham et al. (2004) showed White and Black faces to White participants while participants were undergoing fMRI brain imaging. They found less amygdala activation when participants looked at faces from their own group than when participants looked at other faces; and since amygdala activation is generally associated with negative emotion, they interpreted this tendency suggesting a negative attitude toward outgroup members (see also Hart et al 1990; and for discussion Ito and Cacioppo 2007).