By Catherine A. Sanderson, Amherst College
We all categorize other people and ourselves based on different personality traits. The subject of personality is a favorite target for pseudo-science, from horoscopes to enneagrams. But for contemporary personality psychologists, the approach most widely accepted is the trait perspective. This approach focuses on describing people in terms of their fundamental traits, meaning their relatively stable patterns of thinking, feeling, and acting.

Marshmallow Test
Imagine yourself as a small child, maybe four or five years old. You are brought into a room and sat at a small table with a plate containing a marshmallow right in front of you. Then, you are given a choice. You can eat this marshmallow right now, or you can wait for 15 minutes and then you will be given two marshmallows to eat. What do you do?
This is the set-up in one of the most famous studies in psychology, often referred to as the ‘marshmallow test’. This study was designed by Walter Mischel, a professor at Stanford University, to study individual differences in delay of gratification. He brought in over 600 children between the ages of four and six, sat them at a table with a tempting marshmallow right in front of them. The researchers then watched through a one-way mirror and recorded how long the kids chose to wait.
Findings of the Marshmallow Test
This study resulted in two really important findings. First, the kids showed a tremendous range of behavior. Some did immediately pop the marshmallow in their mouth, so the study ended in like five seconds. But other kids did something remarkable—they waited. Many of these kids tried to distract themselves in some way: they looked at the ceiling, they looked at their feet, some of them sang songs. And about one-third of the kids did in fact wait for 15 minutes, and then got to eat two marshmallows. This study illustrates that even small kids show real individual differences in their ability to wait, to delay gratification.
However, the second finding from this study was even more remarkable. The researchers, who published their first paper in 1970, continued to follow up these kids over time and found that kids who delayed eating the marshmallow differ from those who didn’t in a number of ways throughout their lives: They had higher SAT scores, lower levels of substance abuse and obesity, greater social skills, and so on. So, this study suggests not only that kids differ from one another, but also that these differences persist for years, even decades.
This study illustrates the power of personality, meaning our unique and relatively stable pattern of thoughts, feelings, and actions.
This article comes directly from content in the video series Introduction to Psychology. Watch it now, on Wondrium.
Trait Theory

A distinction between introversion and extraversion was highlighted in the 1920s by Carl Jung, whose personality types soon morphed into the unreliable Meyers-Briggs set of 16 types, that’s been debunked as scientifically invalid, overlapping, and lacking predictive power.
What psychology uses instead is a statistical technique known as factor analysis to group what are literally thousands of everyday words describing people’s traits into a much smaller number of basic units or factors.
The Five-factor Model
Within trait theory, the most commonly used model created with factor analysis is known as the five-factor model, often referred to informally as The Big Five. This model was originally proposed in the 1960s but then widely ignored until the 1980s, when Robert McCrae and Paul Costa published a series of papers showing that people’s traits grouped in consistent ways, were stable over time, and could predict behavior.
At the time, this was actually seen as a revolutionary finding in psychology. The field of psychology had largely dismissed the role of individual differences in predicting behavior and emphasized the power of the situation. Evidence from classic social psychology studies conducted in the 1960s and 1970s—Milgram’s obedience study, Zimbardo’s prison study—had clearly demonstrated how situational factors exerted a strong influence on behavior. Thus, personality traits had come to be seen as largely unimportant.
By contrast, the work by Costa and McCrae pointed to relatively stable patterns of thinking, feeling, and acting that made people quite different from one another. According to their five-factor model, people’s traits group into five basic dimensions: openness, conscientiousness, extraversion, agreeableness, and neuroticism.
The Big Five
The five-factor model says all people in the world (and this research has been validated across cultures) can be described in terms of their personality on where they fall on just five fundamental traits:
Openness: People who are high on openness are willing to try new things and are open to different ideas and beliefs; those who are low on this dimension feel uncomfortable in new situations and prefer familiar and predictable environments and routines.
Conscientiousness: People who are high on conscientiousness are hard-working, well-organized, and punctual; those who are low on conscientiousness are less focused on being tidy and punctual, and more likely to engage in impulsive behavior.
Extraversion: People who are extraverted are out-going, socially confident, and eager to meet new people; those who are low on this dimension are quiet and prefer spending time in smaller social groups.
Agreeableness: People who are agreeable are friendly, likeable, and altruistic; those who are low on this dimension are less concerned with pleasing people, more suspicious of other people’s motives, and more focused on their own self-interest.
Neuroticism: People who are high on neuroticism are anxious, fearful, and tend to focus on negative aspects of most situations; those who are low on neuroticism remain calm during times of stress and are less likely to worry about and dwell on problems they are facing.
Each of these traits is measured on a continuum in which some people fall at extreme ends, but most fall somewhere in-between. So, each of us could be assessed as to where we fall on each of these five dimensions. Even more importantly, these traits also are pretty good at predicting behavior.
Common Questions about the Various Personality Trait Theories
The ‘marshmallow test’ was designed by Walter Mischel, a professor at Stanford University, to study individual differences in delay of gratification.
According to the five-factor model, people’s traits group into five basic dimensions: openness, conscientiousness, extraversion, agreeableness, and neuroticism.
People who are extraverted are out-going, socially confident, and eager to meet new people; those who are low on this dimension are quiet and prefer spending time in smaller social groups.