The diagnosis of Attention-Deficit/Hyperactivity Disorder requires that at least some hyperactive or inattentive symptoms must have been observed before what age?

When Jerry thought he was the only person who was assigned the job of contacting alumni for a 15-year reunion, he spent several hours on the phone each evening trying to reach members of his graduating class. When he learned that eight other people were also working on contacting the alumni, he spent only 30 minutes each night making phone calls. The process that would BEST explain the decrease

in Jerry's effort when he learned that he was working as part of a larger group, is a. social interference. b. social loafing. c. the bystander effect. d. social dissonance.

In the context of operant conditioning, any stimulus that increases the probability that a preceding behavior will be repeated is known as a(n) ________.

Fill in the blank(s) with the appropriate word(s).