Chapter 1 : Introduction

When presented with only correlational evidence, the investigator can only hypothesize about possible causal factors underlying a relationship between variables. A stage wherein the investigator thinks about possible causal factors and "tries them out" as explanations, perhaps during discussions with other researchers, is often a preliminary step to doing research which may provide evidence for the factors responsible for the reported relationship. For each of the following reports of covariation, identify a possible causal factor; that is, speculate on "why" these events are correlated.

1. A study of nearly 5,000 Swedish women (20 to 44 years old) revealed that couples who live together before marriage have an 80 percent higher probability of getting divorced than do married couples who do not live together before marriage (Behavior Today, December 21, 1987).

2. Married women are found to suffer from depression more than men. However, the greater is marital compatibility the less the risk of depression among women (Behavior Today Newsletter, July 28, 1986).

3. In the late 1980s the National Institutes of Health sponsored a conference to assess available data regarding the healing power of pets.'' The idea is that having pets is good for you. One investigator reported that among ninety-two coronary patients, pet owners were more likely to be alive one year after discharge from a coronary heart unit than were people who do not own a pet (Science, September 25, 1987).