In the 1970s, Mary Ainsworth formulated the Strange Situation procedure to observe and study the attachment relationships between mothers (or caregivers) and children. This model of classification applies to children between ages 9 and 18 months and includes "attachment styles," such as secure, anxious-avoidant, and anxious-ambivalent.

Mary Ainsworth is a developmental psychologist who came up with the Strange Situation paradigm to observe how children react when their caregiver re-enters the room after having left prior. The four main attachment styles are secure, avoidant, disorganized, and resistant.

The Apgar Scale is composed of five measures, each graded with an integer from 0 through 2; in total, there is a total possible range of 0 to 10, with a higher score indicating better health. Though it is not often attained, a 10 is the highest possible score on this scale.

Secure, avoidant, ambivalent, and disorganized are the four categories of attachment determined by Mary Ainsworth. As revealed by "the strange situation," children with secure attachments are upset when the mother leaves and soothed when she returns. Children with avoidant attachments ignore the mother when she leaves and ignore her when she returns. Children with ambivalent attachments are upset when the mother leaves and aren't soothed when she returns. Children with disorganized attachments react to the strange situation in ways not covered by the other three categories.

Mary Ainsworth conducted the "strange situation" experiment, in which young babies were briefly separated from their mothers in an unfamiliar laboratory environment. She used this scenario to assess the infants' responses to separation, and out of these responses she came up with 4 attachment styles. These styles of attachment continue to be used by psychologists today.

Eleanor Gibson developed the visual cliff apparatus to assess whether infants' depth perception was an innate or learned ability. Her results indicated that infants could perceive depth using visual clues even before they were able to crawl (around 6 months).

The Milgram experiment studied obedience to authority figures and conscience, and the Lab Coat experiment is a common alternate name for the Milgram experiment. The Prisoner experiment studied the psychological effects of being both a prisoner and prison guard. The Bobo doll experiment was the collective name for a series of experiments investigating childhood behavior modeling.

The longitudinal research design is popular in developmental psychology research because it allows the researcher to observe the same participants over a long period of time. For example, a longitudinal research study could look at how exposure to toxic chemicals in infancy impacts subjects many years later (in childhood, adolescence, and beyond!).

Developmental psychology looks at the physical, cognitive, and social development that occurs throughout a lifespan. In doing so, developmental psychologists are faced with three engaging issues: nature and nurture, continuity and stages, and stability and change. Nature and nurture is a focus that examines how our biology interacts with our environment and experiences to influence our development. Continuity and stages examines which parts of development are gradual and which are clearly divided by stages via distinct changes. Stability and change looks at which traits persist throughout a lifespan versus those that change (e.g.. temperament and personality has been observed to become more stable as one gets older as opposed to social attitudes, which do not). The other options are incorrect because they are related to Darwin's theory of natural selection.

Naturalistic observation is research done in the natural environment of the subjects instead of the field. There is no manipulation of variables in this type of observation.

Individual case studies are not particularly common in developmental psychology research because the field of developmental psychology seeks to explain typical developmental trajectories among larger groups of people. Case studies are more common in clinical psychological research, in which psychologists will discuss unique cases and how they treated them.