The 'roving eye' effect is the propensity of people in relationships to 'eye up' members of the opposite sex. I fitted 20 people with incredibly sophisticated glasses that tracked their eye movements .Over four nights I plied them with either 1, 2, 3 or 4 pints of strong lager in a nightclub and recorded how many different people they eyed up (i.e., scanned their bodies). Is there an effect of alcohol on the tendency to eye people up?