How do we know? Psych 231: Experimental Psychology

Exercise: How do we know? Write down two things that you “know”. Write down HOW you “know” those things.

Methods of Inquiry Type of knowledge –Objective - having “real” existence outside of a person’s mind –Subjective - existing in a person’s mind Ways of knowing –Analysis - finding supporting evidence –Acceptance - taking as true

Methods of Inquiry

The scientific method –We’ll learn how to test and analyze claims about behavior using scientific methods of systematic observation and experimentation.

Scientific Method –write down two generalizations that you have observed about people’s behavior. Step 1: Observation –Pay attention to the world around you, look for generalizations –Two kinds of generalizations Descriptive generalizations – just describe how it is/what was seen, without making predictions Cause and effect generalizations – makes predictions about the observed relationship between two (or more) things.

Scientific Method Step 2: Develop a theory or hypothesis –An explanation for the observed behavior(s) May be based on past research, common sense, intuition, logic, etc.

Scientific Method Step 3: Generate a testable prediction –Need to specify how your hypothesis can be tested. –Falsification is at the heart of the scientific method –More on this next lecture

Scientific Method Step 4: Make systematic observations –Observational and experimental methods What are the relevant variables? How do we measure the variables? What needs to be controled? –Much of the rest of this course deals with these

Scientific Method Step 5: Evaluate your evidence –Refutes theory –Supports theory –Leads to the revision of the theory –Consider alternative theories

The importance of a critical eye There are always alternative explanations: –Coke vs. Pepsi

The Pepsi Challenge Pepsi did a taste test in Dallas (Coke had a 3:1 lead). Wanted to find out if drinkers really preferred Coke or if it could be attacked by advertising. Chose set of Coke drinkers, gave glass with Coke and one with Pepsi Any problems with this experiment? Should not actually label like that – Why?

The Pepsi Challenge Next version: labeled by letters – M (Pepsi) and Q (Coke). Found that more than half chose Pepsi. OK? Turns out that it is not so OK. What if some letters preferred more than others? Could this account for the results? Yes Seems strange, but how would you test?

The Pepsi Challenge Pepsi did the test again, need to control for label, so they counterbalanced order. To be convincing then, for half the tasters the labels should be one way and for the other half the other. Then can rule out label preference. (What about order that things are tasted? )

The importance of a critical eye There are always alternative explanations: –Coke vs. Pepsi –Psychic Uri Geller

Psychic watch repair Uri Geller, famous psychic. In Australia (and other places), would “heal” watches in audiences and even over radio. How did he do it?  Geller’s claim: Psychic energy from him.

Psychic watch repair Problem: Someone else replayed tape of the broadcast and found it worked then too Alternative explanation: Old watches usually not working because oil gummed up. Heat of hands is sufficient for a short time. Experimental Solution: Add a control group – a group of people with broken watches who do everything the same (including covering the watch) but don’t get Uri’s psychic energies Geller relied on people believing that since watches had not been working that it was his energy, as opposed to the other changes (such as holding) that was responsible

Next week Getting ideas for your experiments Read chapter 2 this weekend