Freud typified personality as a struggle in which one of the personality structures is caught in the middle of the conflict between the other two structures. This part caught in the middle is the

When do infants first exhibit a social smile?

a. at birth b. at the second or third month c. at the sixth or seventh month d. at a year

If researchers are working to develop drugs that slow or limit the damage caused by Alzheimer's disease, the neurotransmitter they most likely would be working with would be:

a. dopamine b. acetylcholine c. GABA d. serotonin