Although attentional bias to drug cues is often quantified by measuring performance on an interference task such as the Stroop task which requires the participant to detect and then respond to a cue, there are a number of other studies which have shown that basic visual metrics of attention such as visual fixation are even more robust markers of attentional bias to drug cues. These visual metrics are affected in multiple classes of drug users including marijuana (Field et al., 2006), alcohol (Miller and Fillmore 2010, 2011), nicotine (Mogg et al., 2003), and cocaine users (Marks et al., 2014). Marks and colleagues (2014), for example, recently demonstrated that cocaine users, compared to non-using controls, visually fixate for a longer amount of time on cocaine-related images, and that this attentional bias was significantly correlated with self-reported lifetime cocaine use. The advantage of visual fixation time as a metric of attentional bias is that it may have higher test-retest reliability than response time in an interference task (Ataya et al., 2012) and that it does not require a motor response (which may
