Personality and Individual Differences: Psychological Measurement 2

Methods of Measurement in Personality and Individual Differences

The most important and frequently used measurement method is self-reports, which are usually structured questionnaires.

  • Self-Reports:

    • Consist of a structured questionnaire. Each participant answers the same set of questions (items).

    • Each item has a fixed set of response alternatives, forming a response scale.

    • The entire questionnaire is a scale that measures something.

    • Example: "How do you like to go out to parties?" with a response scale of "agree" or "disagree" on a scale from one to five.

    • Personality inventories (or questionnaires/scales) typically assess multiple personality traits.

    • Examples: The Big Five Inventory, scales measuring specific traits like aspects of perfectionism.

    • Each trait is assessed using several items to increase reliability and content validity.

    • Using several items enables you to have a wide range of behaviors, feelings or thought that you can ask participants about.

    • More items usually indicate higher reliability and content validity.

Reverse-Coded Items

  • Many personality researchers recommend using reverse-coded items in self-reports.

    • These items capture the opposite of the characteristic being measured.

    • Example: If measuring extraversion (outgoing, likes parties), include an item like "I like to stay in and watch TV by myself."

  • Reverse-coded items help:

    • Balance out the tendency to agree (acquiescence), preventing those who tend to say "yes" to everything from getting high scores.

    • Encourage participants to read more carefully.

Strengths and Weaknesses of Self-Reports

  • Strengths (+):

    • Efficient and easy to administer (paper, online survey).

    • Low cost.

    • Mostly accurate, as people have good self-knowledge and are often willing to provide information about themselves.

  • Weaknesses (-):

    • Easily faked or distorted, especially when something is at stake (e.g., job application).

    • People may respond in a socially desirable way.

  • Self-reports are valuable because people usually know themselves well, especially for less-visible traits.

Self-Report Example (HEXACO Gentleness Facet)

  • Instructions: Read each statement and decide how much you agree or disagree.

  • Response scale: 1 (strongly disagree) to 5 (strongly agree).

  • Example Items:

    • "People sometimes tell me that I'm too critical of others."

    • "I generally accept people's faults without complaining about them."

    • "I tend to be lenient in judging other people."

    • "Even when people make a lot of mistakes, I rarely say anything negative."

  • Note: Items 2, 3, and 4 capture gentleness; item 1 is reverse-scored.

Reverse Scoring

  • In the example, item 1 ("People sometimes tell me that I'm too critical of others") needs to be reverse-scored.

  • A response of 5 (strongly agree) should be recoded to 1, and vice versa, before aggregating the scale.

  • High score shows low gentleness and low score shows high gentleness.

Observer Reports

  • Analogous to self-reports, but someone else provides information about the target person.

  • Observer can be a spouse, parent, friend, colleague, or classmate who knows the target well.

  • Advantages:

    • May be more objective (less biased) than self-reports.

    • Others may know us better than we know ourselves.

  • Disadvantages:

    • Some aspects of personality may not be observable.

    • Observations are done in a limited range of contexts.

  • Example: A friend you go out with may know your extraversion, while a friend you study with knows your conscientiousness.

Observer Report Example

  • Similar to a self-report, but statements are about the person being rated.

  • Example: Instead of "I'm sometimes too critical of others", it's "He or she is sometimes too critical of others".

  • Same response scale (strongly disagree to strongly agree).

  • Item 1 needs to be reverse-scored.

Direct Observations

  • Directly observing a person's behavior and noting its frequency and intensity.

  • Example: Observing children in a nursery setting for extroverted behavior.

  • Can be done in natural (e.g., kindergarten) or artificial (e.g., lab) settings.

  • Advantages:

    • It can be very informative

  • Disadvantages:

    • Time-consuming, expensive and a lot of effort.

    • Requires training raters.

    • Behaviors need to be aggregated over multiple indicators, times, and situations.

  • More behaviors, more occasions, more raters, and more reliable direct observations.

  • If you want to capture a trait, a trait that is something that generalizes across different situations, across time, you need more behaviors, you need more times, you need more situations.

Bio Data (Life Outcome Data)

  • Recordings from a person's life relevant to personality.

  • Examples:

    • Phone bills

    • Speeding tickets

    • Grade point average

    • Sales records

    • Number of diplomas

    • Income

    • Death

  • Advantages:

    • Objective.

  • Disadvantages:

    • Sometimes it's not clear what information is relevant for, so what characteristic, what personality characteristic this actually captures, and how accurate this information is for the personality trait of interest.

    • It's not always clear what personality characteristic is being captured.

  • Often used to illustrate the predictive validity of personality measures, especially self-reports.

  • Example: Using extraversion to predict sales records.

Summary

  • Scientific study of personality requires understanding methods of measurement.

  • Main methods: self-reports, observer reports, direct observation, and bio data.

  • Need to understand the differences, strengths, and weaknesses of each method.