Attention Deficit and Hyperactivity Disorder (ADHD) is a common disorder, estimated as afflicting 4-6% of the adult population. Latent Inhibition (LI) is a robust phenomenon that is demonstrated when a previously inconsequential stimulus is less effective in a new learning situation than a novel stimulus. Attentional theories of LI state that unattended stimulus preexposures reduce stimulus salience and subsequent associability. A relationship between LI and the dopaminergic system is suggested since dopamine-agonists weaken the LI effect, and dopamine antagonists strengthen it. The effects of medication for ADHD on LI are of interest, since dopamine agonists should weaken LI, but the improvement in attention should potentiate it. To date, only two studies, both with children, have examined the relationship between ADHD and LI.

In the present study, we will compare the LI effect in 100 adults with ADHD, with and without medication, as well as compare them to a matched healthy control group. In addition, all the participants will be administered the Schizotypal Personality Questionnaire, State & Trait Anxiety Inventory, Beck Depression Inventory, the Baron-Cohen Autistic Questionnaire, and the Similarities sub-test from WAIS-R. The LI procedure will be administered to both groups twice with two equivalent versions of the procedure (order counterbalanced). The ADHD patients will take part in the first version of the procedure without medication and in the second version 1.5 hours after taking the medication; the controls will have the same time interval between versions, but without the medication administration. Results will be presented at the meeting.