At the heart of the continuity versus discontinuity debate lies the question of whether development is solely and evenly continuous, or whether it is marked by age‐specific periods.

"Nature versus nurture" is a psychology term related to whether heredity or the environment most impacts human psychological development (behavior, habits, intelligence, personality, sexuality, aggressive tendencies, and so on).

Personality Structure [edit] Sigmund Freud determined that the personality consists of three different elements, the id, the ego and the superego.

The process by which libidinal energy is expressed through different erogenous zones during different stages of development.

Fixation refers to a persistent focus of the id’s pleasure-seeking energies on an earlier stage of psychosexual development. A fixation occurs when an issue or conflict in a psychosexual stage remains unresolved, leaving the individual focused on this stage and unable to move onto the next. Individuals with an oral fixation may have problems with drinking, smoking, eating or nail biting.

Erikson’s theory which emphasizes the importance of social relationships and conscious choice throughout eight stages of development.

Behaviorism, and Social Cognitive.

A simple form of learning in which an organism learns to engage in behavior that is reinforced.

A simple form of learning in which one stimulus comes to bring forth the response usually brought forth by a second stimulus by being paired repeatedly with the second stimulus.

The stage theory that holds that the child’s abilities to mentally represent the world and solve problems unfold as a result of the interaction of experience and the maturation of neurological structures.

Information processing theory describes how information is received, processed, stored and then retrieved in the human brain.

Attachment theory is a concept in developmental psychology that concerns the importance of "attachment" in regards to personal development. Specifically, it makes the claim that the ability for an individual to form an emotional and physical "attachment" to another person gives a sense of stability and security necessary to take risks, branch out, and grow and develop as a personality.

Correlation research is a form of analysis in which you correlate one variable with another to determine if there is a relationship between them.

Experimental Research involves manipulating the independent variable in some type of controlled situation (preferably a laboratory) so that precise measurements can be taken. It is used to advance our knowledge to give us a better understanding of behavior. Psychological experiments do not discover, prove, or disprove cause-effect relationships. Psychological experiments are used to test hypotheses. If by common sense we believe something is true, we can use psychological experiments to test and retest those hunches. If the results can be replicated, we become more confident about what we believe to be true. In other words, psychological experiments can tell us how accurate our beliefs are.

Random assignment refers to the use of chance procedures in psychology experiments to ensure that each participant has the same opportunity to be assigned to any given group. Study participants are randomly assigned to different groups, such as the experimental group, or treatment group.

A condition in a scientific study that is manipulated so that its effects can be observed.

A group made up of subjects who receive a treatment in an experiment.

A group made up of subjects in an experiment who do not receive the treatment but for whom all other conditions are comparable to those of subjects in experimental group.

Cross-sectional designs are sampled groups taken and examined from a continuum to determine if there is a difference between different sections of the continuum. This is unfortunately a little vague because different continuums can be used. For instance, if you made $100,000 a year and I made $10,000 a year, then there is likely to be differences between us.

Cohort refers to a group of individuals sharing certain significant social characteristics in common, such as sex, time, and place of birth.

Similarities in behavior among a group of peers that stem from the fact that group members were born at the same time in history.

A longitudinal design is a research study where a sample of the population is studied at intervals to examine the effects of development. In a longitudinal design, you have a group of people and you study something about them. Then you collect their contact information. After a set amount of time - be it weeks, months or years - the participants are called and asked to return.

Subject attrition may be the slow loss of subjects through circumstance.

Practice effects refer to gains in scores on cognitive tests that occur when a person is retested on the same instrument, or tested more than once on very similar ones.

Erik Erikson (1902 - 1994) was a developmental psychologist and psychoanalyst, best known for formulating the Psychosocial Stages of Development which outlined personality development from birth to old age. He also coined the term Identity Crisis which describes when a person loses their sense of self.

Piaget (1936) was the first psychologist to make a systematic study of cognitive development. His contributions include a theory of cognitive child development, detailed observational studies of cognition in children, and a series of simple but ingenious tests to reveal different cognitive abilities.

John Watson (1878 - 1958) is often called the Father of Behaviorism, which emphasizes objective and observable data such as people's behavior and reactions, as opposed to internal process that cannot be observed like mental states, or thought processes.

John Bowlby (1907 - 1990) was a psychoanalyst (like Freud) and believed that mental health and behavioral problems could be attributed to early childhood.

Albert Bandura (1925 - ) is best known for his Social Learning Theory, which states learning happens by observing others and modeling their behaviors.

Genetic material that takes the form of a double helix composed of phosphates, sugars, and bases.

Genes are the basic unit of heredity. Genes are composed of deoxyribonucleic acid (DNA).

Rod-shaped structures composed of genes that are found within the nuclei of cells.

The form of cell division in which each chromosome splits lengthwise to double in number. Half of each chromosome combines with chemicals to retake its original form and then moves to the new call.

The form of cell division in which each pair of chromosomes splits so that one member of each pair moves to the new cell. As a result, each new cell has 23 chromosomes.

A chromosome in the shape of a Y (male) or X (female) that determines the sex of the child.

Dominant inheritance means an abnormal gene from one parent can cause disease, even though the matching gene from the other parent is normal. The abnormal gene dominates. Each child's risk is independent of whether their sibling has the disorder or not.

A chromosomal abnormality characterized by mental retardation and caused by an extra chromosome in the 21st pair.

A chromosomal disorder found among males that is caused by an extra X sex chromosome and that is characterized by infertility and mild mental retardation.

Twin studies are part of the methods used in behavior genetics, which includes all data that are genetically informative – siblings, adoptees, pedigree data etc.

Adoption studies are one form of clinical genetic study designed to evaluate genetic and environmental influences on phenotype. In adoption studies the index cases and controls are adoptees.

The heredity of complex characters that are determined by a large number of genes, each one usually having a relatively small effect.

Twins that derive from a single zygote that has split into two; identical twins. Each MZ twin carries the same genetic code.

The presence of any given condition such as HIV in both members of a couple. In genetics, the presence of a phenotype such as asthma in both members of a twin pair.

A cell that is produced by the male sexual organs and that combines with the female's egg in reproduction fluid that is produced by the male sexual organs which contains sperm cells.

A mature female reproductive cell, especially of a human or other animal, that can divide to give rise to an embryo usually only after fertilization by a male cell.

The union of a sperm cell and an ovum that occurs when the chromosomes of each of these cells combine to form 23 new pairs.

One of the two Fallopian tubes that transport the egg from the ovary to the uterus (the womb). In the diagram, the Fallopian tubes are not labeled but are well shown running between the uterus and ovaries.

A diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.

A stage within the germinal period of prenatal development in which the zygote has the form of a sphere of cells surrounding a cavity of fluid.

The period of development between conception and the implantation of the embryo.

The stage of prenatal development that lasts from implantation through the eighth week of pregnancy; it is characterized by the development of the major organ systems.

Environmental influences or agents that can damage the embryo or fetus.

A cluster of symptoms shown by children of women who drank heavily during pregnancy, including characteristic facial features and mental retardation.

When a child is oriented feet first in the mother's uterus just before delivery.

The diameter of the opening of the cervix in labor as measured on vaginal examination. It is expressed in centimeters or finger breadths; one finger breadth is approximately 2 cm. At full dilation the diameter of the cervical opening is 10 cm.

The phase at the end of labor in which the fetal head is seen at the introits of the vagina. The labia are stretched in a crown around the head just before birth.

An educational approach to labor and delivery in which the parents are specially prepared for the event. The aim is for the mother to be awake and cooperative and for the father to assume an active and supportive role during the birth of their child.

Delivery of a baby by abdominal surgery.

Less oxygen than required.

Low birth weight (LBW) is defined as a birth weight of a live born infant of less than 2,500 g (5 pounds 8 ounces) regardless of gestational age.

Born before the full term of gestation. Also referred to as preterm.

Small-For-Date Babies (or small for gestational age babies) are infants born small compared to other babies carried in the womb for the same amount of time. These infants fall in the lowest 10th percentile for weight (meaning 90% of babies the same age weigh more) and face higher risks of complications at birth, during infancy, and later in life. Some small babies are perfectly healthy, but others may be small due to a disorder or restricted growth in the womb.