By _____ years of age, pairs of children begin to select each other as mutually preferred playmates

What are two primary roles of glial cells?

A) Forming myelin and forming the blood-brain barrier B) Shaping cells and moving new neurons into place C) Regulating metabolic activity and serving as pain detectors D) Monitoring neural transmission and releasing hormones in the brain

Which of the following is true about the development of sadness in infants?

a. Infants with depressed mothers are more likely to show sadness because of a genetic predisposition to depression. b. Infants with depressed mothers are less likely to show sadness because they use social smiles to attempt to cheer up their mothers. c. Infants with depressed mothers show the same level of sadness as other infants because the development of emotions is largely innate. d. Infants with depressed mothers are more likely to show sadness because they see more sadness from their mothers.