How can we get the answers to our questions about development?

What is age- related Change?

Evaluation of Research Goals of Aging Research Types of Methods Developmental Designs Strengths & Weaknesses of typical designs Other methodological issues Outline:

The Major Question in Aging Research: Are differences we Are differences we observe attributable observe attributable to age? to age?

Two Approaches

Experimental Psychology Manipulate variables and measure effects on dependent variables. (Individual differences are noise)

Differential Psychology Looks at relationships among individual differences measured on psychological variables. (Individual differences object of study)

Experimental Experimental: Look for interactions between age (as an independent variable) and other manipulated independent variables. (Deals with means)

Behavior Young Old Level 1 Level 2 Other Variable

Differential Differential: Account for age-related variance on some psychological variable by individual differences on some other variable. (Deals with variance)

Age Behavior Other Variable a b e.g., b / a+b

How do we evaluate research? Statistical Significance Reliability Internal Validity (control) External Validity (generalizability)

Independent Variable Dependent Variable Dependent variable = f ( Independent variable )

Independent Variable Dependent Variable Other Variable Other Variable

Age Behavior

Generalizability Age Behavior Independent Variable Dependent Variable (SAMPLE) (POPULATION)

Threats to validity: Selection An example: Young = College Students Young = College Students Old = Nursing Home Residents Old = Nursing Home Residents

Threats to validity: Selection Internal Validity LOW because don’t differ in just age LOW because don’t differ in just age External Validity LOW because groups are not representative LOW because groups are not representative

Threats to Validity: Matching Young Middle-aged Old Excellent Poor HEALTH STATUS AGE MATCHED GROUP

Research Designs AGE DIFFERENCES Comparisons of different people at different ages. Comparisons of different people at different ages. AGE CHANGES Comparisons of the same people at different points in time. Comparisons of the same people at different points in time.

HISTORICAL TIME CHRONOLOGICAL AGE Age, Cohort, & Time of measurement

HISTORICAL TIME CHRONOLOGICAL AGE Cross-sectional (Differences)

HISTORICAL TIME CHRONOLOGICAL AGE Longitudinal Changes

HISTORICAL TIME CHRONOLOGICAL AGE Time Lag Design

HISTORICAL TIME CHRONOLOGICAL AGE Age, Cohort, & Time of measurement Longitudinal Design Time -Lag Design Cross Sectional Design

Cross-sectional Designs Age and Cohort confounded Age and Cohort confounded Time-Lag Designs Time of measurement and Cohort confounded Time of measurement and Cohort confounded Longitudinal Design Age and Time of Measurement Confounded Age and Time of Measurement Confounded

Age Height Longitudinal Cross-sectional

Historical Time Height Time-lag Age Height Longitudinal Cross-sectional

Discrepant Results? Repeated testing Differential representativeness Differential impact of environmental change Age Behavior Longitudinal Cross-sectional

Sequential designs: 1940 Cohort 1930 Cohort 1920 Cohort Time of Measurement Group A Group B Group C 40 years 50 years 60 years Group D Group E Group F 50 years 60 years 70 years Group G Group H Group I 60 years 70 years 80 years

Cohort-sequential Design 1940 Cohort 1930 Cohort 1920 Cohort Time of Measurement Group B Group C Age 50 Age 60 (Same Ss as in B) Group D Group E Age 50 Age 60 (Same Ss as in D)

Time-sequential design 1940 Cohort 1930 Cohort 1920 Cohort Time of Measurement Group B Age 50 Group D Group E Age 50 Age 60 (Same Ss as in D) Group G Age 60

Cross-sequential design 1940 Cohort 1930 Cohort 1920 Cohort Time of Measurement Group A Group B Age 40 Age 50 (Same Ss as in A) Group D Group E Age 50 Age 60 (Same Ss as in D)

Sequential designs: 1940 Cohort 1930 Cohort 1920 Cohort Time of Measurement Group A Group B Group C 40 years 50 years 60 years Group D Group E Group F 50 years 60 years 70 years Group G Group H Group I 60 years 70 years 80 years

Discuss the advantages and disadvantages of longitudinal studies of aging. Can we talk about age “change” when we only have cross-sectional data? DISCUSSION TOPICS:

Longitudinal Study People tested are of the same age group. Baseline Testing and Follow Up testing The purpose is to measure age related changes.

Cross-Sectional Study Comparing groups of people of different ages. Each person is tested only once Measures age related differences

Term Definitions Internal Validity - extent to which an independent variable determines the outcome of an experiment.

Term Definitions Threat of Selection - when the procedures used to select individuals for research resulting in extraneous differences in the groups selected for study.

Term Definitions Threat of History - during the time between testing an individual may experience something that changes their behavior.

Term Definitions Threat of Testing - taking a test on one occasion can affect test performance on subsequent occasions

Longitudinal Studies Advantages No threat of selection or cohort effects individuals from a single cohort form the study’s participant pool

Longitudinal Studies Advantages Allows investigators to track changes that take place within individuals over a long period of time.

Longitudinal Studies Advantages Better statistical power

Longitudinal Studies Disadvantages Time Consuming History Threat/Testing Threat Selective dropout - over the course of the study individuals may choose not to participate for a variety of reasons.

Longitudinal Studies Disadvantages Individuals difficult to keep up with. (Ex: relocation, incarceration, death -especially with studies of the elderly) Obsolescence of methods

Longitudinal Studies Disadvantages (cont.) Researcher Problems - Difficult to control all aspects of testing protocol Some data collectors don’t use correct procedures Very long term studies may have high turnover so is difficult to keep up with the training

Longitudinal Studies Disadvantages (cont.) Possibility of investigator’s view of problem changes Another investigator publishes results of a similar study before your investigation concludes. Funding may be difficult to obtain, grants are stressful and time consuming

Cross Sectional Studies Advantages Not as time consuming, excessive study can be concluded in a few months.

Cross Sectional Studies Advantages Free of history threat - everyone only tested once

Cross Sectional Studies Advantages Free of testing threat - everyone only tested once

Cross Sectional Studies Disadvantages Do not allow the measurement of age-related change. They determine whether one age group of people differs from another age group.

Cross Sectional Studies Disadvantages No way to control cohort effects or other extraneous factors

Cross Sectional Studies Disadvantages Threat of selection

Can we talk about age “change” when we only “change” when we only have cross-sectional have cross-sectional data? Why? data? Why? End of Class Discussion