['To apply a new paradigm using transient changes to visual scenes to explore information processing biases relating to "social" levels of alcohol and cannabis use.', 'Male and female student volunteers (n = 200) not self-reporting substance-related problems.', 'Quiet testing areas throughout the university campus.', 'A flicker paradigm, for inducing change blindness with lighter and heavier social users of alcohol (experiment 1, n= 100) and social users and non-users of cannabis (experiment 2, n= 100), explored the associations between habitual level of use and the latency to detection of a single substance-related or neutral change made to a scene of grouped substance-related and neutral objects.', 'Alcohol use was measured as the number of units of the heaviest drinking day from the previous week; cannabis use as the number of months of use in previous 12. Change-detection latency comparisons were used to evaluate processing biases.', 'In both experiments, (i) heavier social users detected substance-related changes quicker than lighter and non-users; (ii) lighter and non-users detected substance-neutral changes quicker than heavier users; (iii) heavier social users detected substance-related quicker than substance-neutral changes; and (iv) lighter and non-users detected substance-neutral changes quicker than substance-related changes.'] Does a flicker paradigm for inducing change blindness reveal alcohol and cannabis information processing biases in social users?