Jerome Kagan has been at the forefront of developmental psychology since joining the Harvard faculty in 1964, and was once listed as the 22d most influential psychologist of the 20th century — right ahead of Carl Jung and Ivan Pavlov. His seminal work, “The Nature of the Child,” was published in 1984 and again in 1994. When he started to work on a third edition in his retirement, he decided that so much had changed, he needed to write an entirely new book. That book, “The Human Spark: The Science of Human Development,” was published in June.
Q. How much of who we are is predetermined by genes?
A. Temperament is important. If this child has this biology then he or she could become [any of] 12 different adults. Now the environment takes over. [It’s not] ‘you’ve got those genes and therefore you’re going to go develop this character and this personality.
Q. What role can parents play?
A. The parent is the first source of a child’s conscience. The parents have an enormous power to say: “I’m going to tell you what’s right and wrong.” To follow up by praising the child when he or she does adopt those values and punishing through criticism the times the child does not.
Q. And as a role model?
A. The child assumes if I share the same features, the same last name, the same color skin, laugh at the same things, then maybe I share some [other] properties my parent has. If my mother is a great writer, maybe I could be a great writer. If my father is an unemployed alcoholic, I am likely to have the same traits.
Q. Today’s parents are told to encourage their children all the time. Is this important?
A. All children have a need to feel they are of some value. The role of parents is to communicate to their children: “Child, I value you.” If not, then the child tells her psychiatrist “My mother didn’t love me” — that makes them feel that there’s something wrong with them and that is a burden on the child and the adult [they eventually become].
Q. Do you think today’s parents pressure their kids too much to succeed?
A. I think that any value system carried to an extreme sows the seeds of undesirable outcomes. Individuality is good — it promotes a sense of responsibility, it promotes a certain level of ambition and competitiveness, but turn up the game and you get extreme greed, you get extreme harshness, you get divorces, you get a lot of bad things, because suddenly you are the best person in the world. It’s hard to find a balance.
Q. Do you think it’s the parent’s fault when a child turns out to have problems with drinking or drugs or whatever?
A. Don’t blame parents if kids get caught up [in bad things]. Good parents have kids who get fouled up.
Q. Do you have concerns about the current generation of kids?
A. Middle class kids with supportive parents, I wish they worried a little less. They see a very competitive world in which it’s tough. They’re on the Internet, Facebook, Twitter, television — the message is the same: There are a lot of people at the trough, jobs are hard to get. This creates an ambience in which you’re in a race all the time. It’s sad. This generation is very tense and worried and too oriented at the target.
Q. You devoted your career to understanding how babies and children develop, but now you’re nearing the other end of the life span yourself.
A. My brain is losing neurons at a very rapid rate. I feel lucky at my age [born in 1929] that I can still have a conversation and remember facts.
Q. But that doesn’t bother you?
A. It just reminds you of your fundamental unimportance, fundamental impermanence. I find that freeing rather than depressing. I don’t have responsibilities to students [anymore]. I have responsibilities just to my wife, that’s it.
Q. You’ve said that in some of your future writing, you want to explore marriage. What is it that fascinates you about marriage?
A. When you’re married 62 years [like I’ve been], the thing mellows. That’s why marriage is so interesting. It changes like the plot of a book. Even though it’s such an old institution, very little wisdom has been written about it. That always surprises me.
Q. Do you have marital advice for others?
A. Don’t ever, ever allow yourself to believe you can change your partner.This interview has been edited and condensed. Karen Weintraub can be reached at email@example.com.