chapter 2

selective attrition

longitudinal samples generally become more biased as the investigation proceeds because of selective attrition. Participants may move away or drop out for other reasons, and those who continue are likely to differ in important ways from those who drop out.

the clinical, or case study

method brings together a wide range of information on one child, including interviews, observations, test scores, and sometimes neurobiological measures. The aim is to obtain as complete a picture as possible of that child's psychological functioning and the experiences that led up to it.

confounding variables

so closely associated that their effects on an outcome cannot be distinguished.

risks versus benefits ratio

But researchers are advised—and often required—to seek advice from others. Committees for this purpose (like the one that evaluated Ron's research) exist in colleges, universities, and other institutions. These institutional review boards (IRBs) assess proposed studies on the basis of a risks-versus-benefits ratio, which involves weighing the costs to participants in terms of inconvenience and possible psychological or physical injury against the study's value for advancing knowledge and improving conditions of life.

validity

For research methods to have high validity, they must accurately measure characteristics that the researcher set out to measure.

practice effects

In addition, with repeated testing, participants may become "test-wise." Their performance may improve as a result of practice effects —better test-taking skills and increased familiarity with the test—not because of factors commonly associated with development.

field experiments

In field experiments, researchers capitalize on opportunities to randomly assign participants to treatment conditions in natural settings

matching

In this procedure, participants are measured ahead of time on the factor in question—in our example, exposure to parental conflict. Then children high and low on that factor are assigned in equal numbers to each treatment condition. In this way, the experimental groups are deliberately matched, or made equivalent, on characteristics that are likely to distort the results.

time sampling

In this procedure, the researcher records whether certain behaviors occur during a sample of short intervals.

ethnography

Like the clinical method, ethnographic research is a descriptive, quali tative technique. But instead of aiming to understand a single individual, it is directed at understanding a culture or a distinct social group through participant observation. (from anthro)

cohort effects

Longitudinal studies examine the development of cohorts — children developing in the same time period who are influenced by particular cultural and historical conditions. Results based on one cohort may not apply to children developing at other times.

naturalistic observation

One approach is to go into the field, or natural environment, and record the behavior of interest—a method called naturalistic observation.

neurobiological methods

Researchers' desire to uncover the biological bases of perceptual, cognitive, and emotional responses has led to the use of neurobiological methods, which measure the relationship between nervous system processes and behavior. Investigators use these methods to find out which nervous system structures contribute to development and individual differences. Neurobiological methods also help researchers infer the perceptions, thoughts, and emotions of infants and young children, who cannot report their psychological experiences clearly.

dependent variable

The dependent variable is the one the investigator expects to be influenced by the independent variable.

independent variable

The independent variable is the one the investigator expects to cause changes in another variable.

microgenetic design

The microgenetic design, an adaptation of the longitudinal approach, presents children with a novel task and follows their mastery over a series of closely spaced sessions. Within this "microcosm" of development, researchers observe how change occurs

natural / quasi-experiments

Treatments that already exist, such as different family environments, child-care centers, or schools, are compared. These studies differ from correlational research only in that groups of participants are carefully chosen to ensure that their characteristics are as much alike as possible.

observer bias

When observers are aware of the purposes of a study, they may see and record what they expect to see rather than what participants actually do.

correlational coefficient

a number that describes how two measures, or variables, are associated with each other.

hypothesis

a prediction drawn from a theory

structured interview

each individual is asked the same set of questions in the same way. This approach eliminates the possibility that an interviewer might press and prompt some participants more than others.

cross-sectional design

groups of people differing in age are studied at the same point in time.

informed consent

guards in place, the committee approved Ron's research. The ethical principle of informed consent —people's right to have all aspects of a study explained to them that might affect their willingness to participate

structured observations

in which the investigator sets up a laboratory situation that evokes the behavior of interest so that every participant has an equal opportunity to display the response.

debriefing

in which the researcher provides a full account and justification of the activities,

sequential designs

in which they conduct several cross-sectional or longitudinal investigations (called sequences ). The sequences might study participants over the same ages but in different years, or they might study participants over different ages but during the same years

internal validity

is the degree to which conditions internal to the design of the study permit an accurate test of the researcher's hypothesis or question.

longitudinal design

participants are studied repeatedly at different ages, and changes are noted as they get older. The

experimental design

permits inferences about cause and effect because researchers use an evenhanded procedure to assign people to two or more treatment conditions.

protection from harm

protection from harm. If there are any risks to the safety and welfare of participants that the research does not justify, then preference is always given to the research participants.

reliability

refers to the consistency, or repeatability, of measures of behavior. To be reliable, observations and evaluations of peoples' actions cannot be unique to a single observer. Instead, observers must agree on what they see

correlational design

researchers gather information on individuals, generally in natural life circumstances, and make no effort to alter their experiences. Then they look at relationships between participants' characteristics and their behavior or development.

clinical interview

researchers use a flexible, conversational style to probe for the participant's point of view.

external validity

the degree to which their findings generalize to settings and participants outside the original study. E

observer influence

the effects of the observer on the behavior studied.

biased sampling

the failure to enlist participants who represent the population of interest.

event sampling

the observer records all instances of a particular behavior during a specified time period.