METHODS IN PSYCHOLOGY An Overview Lawrence R. Gordon Psychology Research Methods I

Something to Start With §According to 1999 statistics reported on Vermont Public Radio, women are not as good at math as men are. §The evidence presented to support this conclusion was that the average SAT math score for women was 40 points lower than the average score for men.

What do you think about this? §What is the explanation behind this finding?

Research questions The effects of __________ on _________ ?

Psychology Research §Research is the search for the relationships between variables. §Two types of variables: l independent variables l dependent variables §Research tries to find the effects of independent variables on dependent variables. l “The effects of IV(s) on DV(s) ?”

Independent Variables §This is the variable of interest because we are trying to find its effects (how does it influence other (dependent) variables?) §Called the predictor variable in some analyses §Can be either manipulated or observed §Examples

Dependent Variables §We are trying to find out how it is affected by other (independent) variables §Called the criterion variable in some analyses §Always observed §Examples

Major Types of Research §Correlational Research l independent variable is observed l dependent variable is observed l allows you to see if the IV and the DV are related l does NOT allow you to make cause-effect statements about the IV and the DV

Types of Research (cont.) §Correlational Research (cont.) l Why no cause-effect conclusions? Nature of relationship between IV and DV is unclear! l IV may cause the DV l DV may cause the IV l The third variable problem: Something else may cause them both

Types of Research (cont.) §Experimental Research l independent variable is manipulated l dependent variable is observed l all other variables are controlled l allows you to see if the IV causes DV l does allow you to make cause-effect statements about the IV and the DV §Example – correlational, then experimental

NPY Disturbances in the Obese Rat §Williams et al. (1992) §Lean and obese rats §The levels of neuropeptide Y (NPY) were measured in the rats by radioimmunoassay §Question l What is the association between NPY and obesity (do obese rats have higher levels of NPY?)

NPY Disturbances (cont.) §Results l Obese rats had higher levels of NPY in the ARC than did than lean rats §What can you conclude? l Did increased NPY cause the obesity? l Did obesity cause the increased NPY? l Did something else cause the increased NPY and the obesity?

NPY Disturbances (cont.) §Conclusion l Increased levels of NPY are associated with obesity in rats. l This is correlational research. l No cause-effect conclusions can be drawn.

NPY Disturbances (cont.) §What was the IV? §How was the IV defined? §What was the DV? §How was the DV defined? §Do you agree with these definitions? §How could the IV and DV be defined differently, yet still ask the same questions?

Induction of Obesity by NPY Administration in Normal Rats §Vettor et al. (1994) §Lean rats §2 conditions l one group was infused with NPY for seven days l one group was infused with vehicle saline solution for seven days

NPY Administration (cont.) §Measured food intake and body weight for 14 days (7 infusion days and the 7 following days) §Questions l Would the rats with NPY infusions eat more? l Would the rats with NPY infusions weigh more? l If so, would this stop when the infusions stopped?

NPY Administration (cont.) §Results l Rats with NPY infusions showed dramatic increases in food intake. l Rats with NPY infusions showed dramatic increases in body weight. l These increases were reversed when the NPY infusions stopped. l Graphic presentations >>>>

Food Intake

Body Weight Increase

NPY Administration (cont.) §What can you conclude? l Did NPY cause the increases in food intake and body weight? l Did the increases in food intake and body weight cause the NPY infusions? l Did a third variable cause both the increases in food intake and body weight and the NPY infusions?

NPY Administration (cont.) §Conclusion l NPY infusions caused increases in food intake and in body weight in lean rats. l This is experimental research. l Cause-effect statements can be made.

NPY Administration (cont.) §What was the IV? §How was the IV defined? §What was the DV? §How was the DV defined? §Do you agree with these definitions? §How could the IV and DV be defined differently, yet still ask the same questions?

MAJOR RESEARCH METHODS §Research begins with a question l “The effect(s) of _____ on _____.” l …but there are many ways to try to answer it! §Research also has implicit or explicit hypotheses: l “If __A__, then __C__.” l A - “antecedent”, C - “consequent” l Falsify: “A, but Not-C” OR “Not-C, but A” §Willems (1969) classifies research methods: l by degree of manipulation of antecedents l by degree of imposition of units on consequents

Let’s simplify… §Major types of research: l Experimental l Correlational l Observational §We’ll soon start with Experimental and procede down the list, because advantages and disadvantages of the other two are best discussed in reference to it!

OVERVIEW: The Research Process: 8 Steps §Develop a research question §Generate a research hypothesis §Form operational definitions §Choose a research design §Evaluate the ethics §Collect data §Analyze data and form conclusions §Report research results