Temperament: Definition & Theories

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  • 0:02 Temperament
  • 1:26 Reactivity
  • 3:20 Rothbart's Three Factors
  • 5:48 Lesson Summary
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Lesson Transcript
Instructor: Natalie Boyd

Natalie is a teacher and holds an MA in English Education and is in progress on her PhD in psychology.

Some personality traits are with us from birth. In this lesson, we'll examine what temperament is, what it can tell us about how a person is likely to turn out, and look at Jerome Kagan and Mary Rothbart's theories about infant temperament.


Kara has a baby girl, Tanya, and she loves to watch Tanya look around and explore the world. Kara can remember when Tanya's older brother, Jim, was a baby, and she's amazed at how differently Tanya and Jim react to the world around them.

For example, Jim was always a fussy baby. If a light shone in his eyes or he heard a loud noise, he would cry and fuss until Kara picked him up and comforted him. But if Tanya has a light in her eyes or hears a noise, she'll wiggle around a little to see if she can find out what is causing the stimuli.

Kara is observing her children's temperament, or personality traits that are innate. Innate traits are the ones that we are born with and have little or nothing to do with our environment. Think about Jim and Tanya: they are being raised by the same people in the same environment, so the differences in their personality are just part of who they are, which makes it part of their temperament.

Because temperament is something that we're born with, it can be measured in infants, like Tanya. Even though she can't talk yet and hasn't really developed what most people think of as a personality, she already has a temperament, which can give insights into what she might be like as she grows.

Let's look closer at two researchers in the area of temperament, Jerome Kagan and Mary Rothbart, and their findings on infant temperament.


Kara has noticed how different her children are from one another. If a loud ambulance drives by the window with lights and sirens flashing, Tanya will calmly look over and try to see what all the fuss is about. But when Jim was a baby, an ambulance like that would make him so scared that he would cry and fuss until Kara could calm him down.

Psychologist Jerome Kagan calls an infant's level of response to stimuli reactivity. To help you remember reactivity, think of the word 'react.' An infant who cries and gets upset in response to stimuli, like Jim, has high reactivity. In contrast, a baby who stays relaxed in response to stimuli, like Tanya, has low reactivity.

Kagan noticed that babies vary in their reactivity from a very early age. Even infants only a few hours or days old seem to have a preset level of reactivity as part of their temperament. In other words, Tanya has low reactivity because that's just who she is and who she's always been.

Kagan also noticed that reactivity in infants is related to their personality when they are older. A baby, like Jim, who is highly reactive as an infant, is likely to be inhibited, or scared of new things and situations, as an adult. In contrast, a baby, like Tanya, who has low reactivity as an infant, is likely to be uninhibited, or open to novelty and secure in new situations, as an adult.

Of course, things can happen to change that; a baby who has low reactivity could have a traumatic event occur to them that leads to their being inhibited in adulthood, and a baby who is highly reactive can be nurtured to be more uninhibited. But all things being equal, Tanya is likely to be less inhibited as an adult than Jim is.

Rothbart's Three Factors

Jerome Kagan isn't the only psychologist who has studied temperament in infants. Psychologist Mary Rothbart has identified three factors that she thinks make up most infant's temperaments.

1. Surgency, or extraversion

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