Jerome Kagan's Research on Temperament in Toddlers

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  • 0:01 Temperament
  • 1:02 Reactivity
  • 2:46 Inhibition
  • 4:49 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.

Why are some people outgoing while others are shy? That's a key question that psychologist Jerome Kagan addressed in his studies on temperament. Watch this video for more information on Kagan's research on temperament in toddlers.


Think about the last time that you were at work, in class or at a party. Chances are you were surrounded by people who were all very different from each other. One guy might be the class clown, always cracking jokes and doing things to get a laugh. A girl might be the quiet, studious type who is always doing what she's supposed to be doing. Maybe another person is the person that everyone goes to for advice; she doesn't speak often, but when she does, everyone listens.

How is it that people are so different? Why do some people enjoy being at a loud party, while others would prefer to curl up with a book in the quiet of their own homes? These are questions that psychologist Jerome Kagan is interested in. He's done a lot of research on temperament, or behavioral and emotional traits that shape the way people react to the world around them.

Let's look closer at two elements of temperament that show up in infants: reactivity and inhibition.


Mike and Missy are twins. Their mother loves to watch them play together. Sometimes, she'll put them on the floor and they'll just lie next to each other, making nonsense sounds, kicking and flailing their arms at each other.

One day, an ambulance drives by the window next to Mike and Missy. The loud siren and flashing lights intrude on the two of them. Their mom notices a distinct difference in the way that they react to the ambulance.

Mike begins wailing and kicking his legs. He cries and waves his arms and is obviously distressed and scared by the loud noises and lights. Missy, though, just looks over at Mike like he's crazy. The noise and the lights don't faze her; she stays relaxed and cool through it all.

One of the areas of research that Jerome Kagan has done on babies is on their reactivity, or the way they respond to stimuli. Remember that reactivity has to do with how they react to sights and sounds.

Mike's reaction to the ambulance is indicative of someone with high reactivity. That is, he becomes distressed when presented with stimuli. Babies with a high reactivity react to new sights and sounds with lots of movement and crying.

Missy, on the other hand, has low reactivity to stimuli. She doesn't really react. She's calm and relaxed and nothing seems to faze her. The level of her reaction to the ambulance is low, hence she's low reactivity.

Reactivity is mostly genetic. It is part of who a baby is from almost the very beginning. Missy and Mike are still babies, but the reactivity aspect of their personalities is already clear.


Missy and Mike might be born with a high or low reactivity, but what happens when a child's natural reactivity combines with the environment in which they are raised? Besides identifying reactivity levels in infants, Kagan's research also linked infant reactivity to inhibition, or how natural a person acts, in adulthood. He believes that adult inhibition is closely related to both genetic reactivity and the environment in which a person is raised.

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