Intervening Variables Intervening variables are hypothetical internal states that are used to explain relationships between observed variables, such independent and dependent variables. Intervening variables are not real things. They are interpretations of observed facts, not facts themselves. But they create the illusion of being facts. learning, memory, motivation, attitude, personality, traits, knowledge, understanding, thinking, expectation, intelligence, intention. EXAMPLES:

Intervening Variables Let’s look again at the experiment by Tolman & Honzik (1930) on latent learning in rats, specifically, the group that received a reward every time they reached the goal box. Not Real? One of the Independent Variables was the number of practice trials the rats received. They got 1 trial per day, so each rat got an increasing number of trials. The Dependent Variable was the number of wrong turns (errors) that rats made on a trial. The following graph shows a relationship between the independent variable and the dependent variable.

Trials (1 Trial per Day) Average Errors Tolman and Honzik, 1930 Practice TrialsErrors Independent VariableDependent Variable Theoretically, an internal state of “learning” intervened between the independent variable and the dependent variable. Learning Intervening Variable It was this state that caused errors to decrease, not the practice trials.

Operational Definitions Practice Trials Errors Independent Variable Dependent Variable Learning Intervening Variable Intervening variables are studied by means of operational definitions, which are descriptions of procedures that are assumed to have some link to the internal state. Operational Definition

Operational Definitions Practice Trials Errors Independent Variable Dependent Variable Learning Intervening Variable Intervening variables have no existence apart from these observed variables. They are just words, interpretations of facts, like theories. Operational Definition

Operational Definitions As explanations of behavior, intervening variables can lead to an error in logic called “circular reasoning” in which you explain something in terms of itself and so don’t get beyond the original facts. Circular Reasoning To avoid circular reasoning, you must have two or more operational definitions of the same internal state, and they must be correlated. Here’s an example of circular reasoning that results from having just one operational definition.

Operational Definitions Circular Reasoning Two rats receive a food reward when they run from the Start box to the Goal box of a straight alley runway. GOAL They get an equal number of practice trials and run equally fast. One day, the rat on the left is observed to run much faster than the rat on the right.

Operational Definitions Circular Reasoning Why the difference in running speeds? GOAL You may want to explain it in terms of “motivation,” defined as an internal state that causes an organism to move toward a goal. More specifically, you could say that the fast rat was “hungrier” than the slow rat.

Operational Definitions Circular Reasoning This is circular reasoning. It sounds like an explanation but it isn’t. GOAL Running speed toward a food reward is a legitimate operational definition of hunger. It’s OK to infer different levels of hunger from running speeds, but it’s circular to then use hunger to explain those running speeds.

Operational Definitions Circular Reasoning Running Speed defines “Hunger” explains X A second operational definition of hunger is needed to break this circle.

Operational Definitions Circular Reasoning Running Speed defines “Hunger” For example, the fast rat may have been deprived of food longer than the slow rat. Hours of food deprivation could be used as an operational definition of hunger. Hours of Food Deprivation defines

Operational Definitions Circular Reasoning Running Speed defines “Hunger” Different levels of hunger could be inferred from the different periods of deprivation, and then these hunger levels could be used to explain the different running speeds without circularity. Hours of Food Deprivation defines

Operational Definitions Circular Reasoning Running Speed defines “Hunger” The more operational definitions you have that are correlated with each other, the more useful would be the underlying intervening variable. Hours of Food Deprivation defines

Operational Definitions Circular Reasoning Questionnaire Responses define “Attitude” By this standard, how useful would you say are the concepts of attitude, intelligence and personality trait? Everyday Behavior defines Correlated?

Observing Internal Events Intervening variables differ from other kinds of internal events that are real and can be directly observed. Conscious experiences are private events that are directly sensed by the individual and not open to observation by others, like self-talk, feelings, and sensations. Biological processes are open to observation by others using appropriate devices, like an EEG machine to measure electrical activity of the brain.