Scientific study of people Two major issues: 1. Measurement of personality –how do we know what a person’s personality is?? ► Will depend on what we think is important and our assumptions about personality (can we self-report, etc.) 2. Scientific study of personality – theory development relies on process of research

Sources of information 1. Observer ratings – measure comes from someone other than the person being assessed ► Interviews, observations of behavior, judgments ► Called O-data 2. Self-reports – person who is being assessed indicates what they think they are like ► Called S-data ► Can have different types of each – will discuss a variety of measures shortly

Measurement 1. Subjective – requires interpretation ► Requires reliability rating – would two raters agree? 2. Objective – not dependent on a judgment ► Often numerical: Likert scale, reaction time, etc.

Subjective measurements ► Example: pirate test for children (in book) ► Birthday party test: 2 year olds running wildly in a gym  Measure activity level  Measure introversion/extroversion  Measure adaptability to new situations/fearfulness = subjective because they require our interpretation

Measurement Subjective assessment ► Measurement that relies on interpretation ► Weaknesses  Different observes may make different judgments ► Strengths  Complex phenomena may be examined and valuable insight gained

Measurement Objective measurement ► Weaknesses  May reduce a complex behavior  May fail to capture all of the important or interesting phenomena ► Strengths  Clear and consistent (reliable)

Reliability = consistency or repeatability of a measure  Once you have one measurement about someone, how confident can you be that you will get the same measurement the second and third time  Reliable measures are precise  Low reliability includes error Example: measuring for window blinds

Types of reliability 1. Internal consistency = reliability within a particular set of observations ► ACT: would expect people to do about the same on first half and second half (split-half reliability) ► Increases as we take repeated measures ► i.e. a function of number of relevant items (the more the better, but also need to be realistic) ► Cronbach’s coefficient alpha  The average of all possible split-half correlations ► Should be about.8 or higher

Types of reliability 2. test-retest reliability = the measure’s degree of consistency on different occasions ► Stability over time – measuring device should be stable ► Example: GRE scores are stable over time. Don’t want GRE scores to fluctuate greatly

Types of reliability 3. Inter-rater reliability = in observer ratings, the person making the rating is the measuring device. Raters who agree  Example: scores on gymnastics or ice skating events

Validity ► Measurements can be highly reliable but mean nothing See colorquiz

Validity Are you measuring what you think you are measuring? Construct validity – does the measure capture the conceptual idea? ► Long process to establish construct validity:  The assessment is related to what is should be related to = convergent validation  The assessment is NOT related to what it should not be related to = divergent validation ► Example: love  Conceptual definition: a strong caring and affection for another person  How do I operationalize this (make this concrete and measurable)  Could use a rating scale, intensity of eye contact, measure behaviors, etc.

Validity ► Criterion-related validation – does our measure predict an outcome ► E.g. does our “love test” predict which couples will get married? ► Content validity = is a test measuring the domain it is supposed to be measuring  In a personality test, am I measuring “personality” or am I measuring “mood.”

Biases that impact validity 1. Response sets – readiness to answer in a particular way a.Acquiescence – tendency to say “yes” or agree b.Social desirability – people tend to want to portray themselves in a positive light ► Some traits are not neutral: honest/dishonest

Biases that impact validity 1. Experiment bias ► Experimenter bias ► Experimenter expectancies 2. Ethnic bias – fails to take into account the relevant culture of person being tested ► E.g. self-esteem/strengths 3. Gender bias – expectations based on gener ► characteristic that is seen as a strength in one group is seen as a weakness in another 4. Barnum effect – tendency to believe vague generalities about one’s personality

Types of personality measures 1. Self-report measures  Usually pencil and paper tests  Most common type of test ► Examples:  Minnesota Multiphasic Personality Inventory (MMPI)  Big-Five Inventory (BFI)

Types of personality measures 2. Q-sort  Person makes comparisons among their own characteristics  Uses a stack of cards with various characteristics  Individual places cards into piles indicating how descriptive it is of him or her

Types of personality measures 3. Judgments by others  Someone else answers questions about the person being measured  Some traits are easier to judge than others ► Example: extraversion ► Motives may be more difficult to judge  Can use ratings from parents, teachers, friends, spouses, psychologists, etc. ► Example: Terman’s longitudinal study of smart kids

Types of personality measures 4. Biological measures  Assumes that the nervous system is an important element of personality ► Modern Biological Measures  Electroencephalogram (EEG)  Positron emission topography (PET) scan  Magnetic resonance imagery (MRI)  Hormonal levels  Chromosomal analysis

Types of personality measures

5. Behavioral observations  Records the actual behavior of a person ► Types of behavioral observations  Simply counting a specific behavior  Coding videotaped interactions  Electronic pagers

Types of personality measures 6. Interviews ► Unstructured interviews  Typically yield rich information, but validity is questionable ► Structured interviews  More valid, but usually do not reveal individual nuances

Types of personality measures 7. Document analysis/life stories ► Involves the careful analysis of writings such as letters and diaries ► Can be a very rich source of information ► Examples:  Allport’s “Letters from Jenny”  Diary of Anne Frank

Types of personality measures 8. Projective tests ► Uses an unstructured stimulus, task, or situation  The goal is to gain access to unconscious motives and concerns ► Examples:  Draw-a-person  Rorschach Inkblot  Thematic Apperception Test (TAT)

Projective tests

Types of personality measures Method used depends on questions being asked and type of information needed and available See chart in book on strengths and weaknesses, p. 58