Variables Variable = something that can change in different conditions in a study VARIABLES HAVE TO VARY!!

Theories and Variables Theories, theoretical constructs, theoretical concepts: exist in your mind Variables: exist in the world Examples: –anxiety (theoretical construct) –number of blinks per minute (variable) –told that you will have to give a speech or not told (variable)

Independent and Dependent Variables Independent Variable “what the experimenter does to the participants” varied by the experimenter (in experimental research) hypothesized cause of changes in the DV “subject” variables “predictor” variables Dependent Variable “what the participants do back” the measured behavior of the participant hypothesized effect of changes in the IV

Confounded Variables Variables that vary (correlate) with the IV Are unwanted alternative explanations (possible causes) for any differences observed in the DV

Examples: Hypothetical (fake) SAD Study 40 participants who reported suffering from SAD were randomly assigned to 2 groups that differed in light exposure. Group 1 (the “light” condition) sat under bright lights for 2 hours each morning. Group 2 (the “no-light” condition) did not. After 3 weeks, a survey measured how depressed each participant felt. The more questions a participant said “yes” to, the more depressed they were assumed to be. Those in the “light” condition were significantly less depressed.

Example: Effects of Metaphor on Memory for Text 40 participants each read 20 stories. Version 1 of each story had the same metaphor used twice in the story. Version 2 had 2 different metaphors used in the story. Each participant read version 1 of half the stories, and version 2 of the other half. After reading the stories, participants recalled sentences from the story. Participants had better memory for the stories that used a single metaphor twice than for stories that used two different metaphors.

Example: Inference and Working Memory Capacity Participants took a test of working memory capacity (a digit span test) and then read a story. The story contained 2 types of potential inferences: forward inferences (inferring what happened next after an event in the story) and backward inferences (inferring why an event in the story happened). Reading times for sentences at the point of the potential inferences were recorded. Longer reading times were interpreted as evidence that readers were making an inference. Participants were divided into two groups for analysis: high working memory capacity (digit span of 8 or more) and low working memory capacity (digit span of less than 8). Participants made more backward inferences than forward inferences, and this was true for both high and low digit span participants.

Types of Variables Categorical –Vary in kind –Labels only Quantitative –Vary in amount –Measurements –Types: Discrete (eg: whole numbers) Continuous –Real vs. apparent limits

Measurement Measurement = assignment of numbers to objects or events according to rules, so that certain properties of the objects/events will be represented by properties of the number system. Some measurement scales map more properties than others

Measurement: Types of ScalesScales Nominal – naming (categorical) Ordinal – ordering Interval – equal intervals (between numbers) without meaningful zero point Ratio – equal intervals with a meaningful zero point