Experimental schedule. Downward facing arrowheads indicate the variety of behavioral testing. Black represents a fixed ITI training session, blue represents a variable ITI test session, and yellow represents locomotor activity testing. Upward facing arrowheads represent drug treatment. Upper row of black arrowheads represent nicotine (0.2 mg/kg, s.c.) or saline, given 20 minutes prior to testing. Lower row of arrowheads represents PCP (3 mg/kg, i.p.; red) or saline (grey) administered 30 minutes prior to testing.