Chapter 1

Psychological Science

The Need for Psychological Science

How do we know what we know?

How do you know that George Washington was the first President of the United States?

How do you know that you really have a stomach?

What makes you sure the sun will rise tomorrow?

How do you know the color of the shirt you are wearing?

How can you be sure there aren’t little creatures inside a computer that make it work?

How do we know what we know?

Authority – we take the word of an expert Reason – deductive an inductive thinking

to arrive at a conclusion Observation – your own experience All three ways of knowing are used by

scientists, but observation must be the basis for knowledge that is scientific

The Limits of Intuition

Hindsight Bias We tend to believe, after learning an outcome,

that we would have foreseen it the “I-knew-it-all-along” phenomenon

Overconfidence We tend to think we know more than we do

Confirmation Bias Our tendency to seek out information that

confirms our previous beliefs and to ignore information that refutes them.

The Scientific Attitude

Critical Thinking thinking that does not blindly accept

arguments and conclusions examines assumptions discerns hidden values evaluates evidence

The Scientific Method

Theory an explanation using an integrated set of

principles that organizes and predicts observations

Usually a statement about relationship between two variables

Hypothesis a testable prediction often implied by a theory

The Scientific Method

The Scientific Method

Replication repeating the essence of a research

study to see whether the basic finding generalizes to other participants and circumstances

usually with different participants in different situations

Replication is made possible by Operational Definitions

The Scientific Method

Operational Definition a statement of procedures (operations)

used to define research variables Example-

intelligence may be operationally defined as respondent’s score on the WAIS Intelligence test.