Which of the following does not fully mature until adolescence, which may be the reason that children have such short attention spans?

The body's major postural muscles are most relaxed during which stage of sleep?

a. REM sleep b. Stage 2 c. Stage 3 d. Stage 4

Dr. Beaudette is studying parent-infant attachment and plans to define attachment in terms of the time it takes for a parent to respond to an infant's cries. Defining attachment in this way would:

a. be a testable hypothesis b. provide empirical verification of the concept c. represent an operational definition d. violate general research ethics