Social users of alcohol and cannabis who detect substance-related changes in a change blindness paradigm report higher levels of use than those detecting substance-neutral changes.

Rationale: Understanding the cognitions underpinning substance use has stalled using the Stroop paradigm. Objective: To employ a novel version of the flicker paradigm for induced change blindness to independently compare information processing biases in social users of alcohol and cannabis. Method: Alcohol and cannabis experiments were independently run. In both, participants were asked to view successively and repeatedly on a monitor two versions of a visual scene (an original and a slightly changed version) until the change was detected. In fact, in both experiments two simultaneous changes competed for detection: a substance-neutral and a substance-related change. Results: In both the alcohol and the cannabis experiments, participants detecting the substance-related change reported higher levels of use than those detecting the substance-neutral change. Conclusion: A substance-related processing bias was independently revealed for both substances. The utility of the flicker paradigm for substance use research is demonstrated as sensitive and quick to administer (taking only 1 min).