RETRIEVAL PRACTICE Take a moment to answer each of these Learning Objective Questions (repeated here from within this section). Then click the 'show answer' button to check your answers. Research suggests that trying to answer these questions on your own will improve your long-term retention (McDaniel et al., 2009).

Developmental psychologists study physical, mental, and social changes throughout the life span. They focus on three issues: nature and nurture (the interaction between our genetic inheritance and our experiences); continuity and stages (whether development is gradual and continuous or a series of relatively abrupt changes); and stability and change (whether our traits endure or change as we age).

The life cycle begins at conception, when one sperm cell unites with an egg to form a zygote. The zygote’s inner cells become the embryo, and the outer cells become the placenta. In the next 6 weeks, body organs begin to form and function, and by 9 weeks, the fetus is recognizably human.
     Teratogens are potentially harmful agents that can pass through the placental screen and harm the developing embryo or fetus, as happens with fetal alcohol syndrome.

Babies are born with sensory equipment and reflexes that facilitate their survival and their social interactions with adults. For example, they quickly learn to discriminate their mother’s smell and sound. Researchers use techniques that test habituation, such as the novelty-preference procedure, to explore infants’ abilities.