Mary-Frances O’Connor: ‘People struggle to understand grief, but it is a byproduct of love’

M ary-Frances O'Connor is an associate professor at the University of Arizona, where she leads the grief, loss and social stress lab, investigating the effects of grief on the brain and the body.

Humans grieve. One of the earliest things we learn is that we are all going to die, so why is it such a shock? A lot of people have struggled to understand why there is grief, and in a funny way, it is a result of love. When we bond with another person, our spouse or our child, we are told that they will always be there for us and we will always be there for them. We can kiss our partner goodbye in the morning and go on our separate ways to work, knowing that we will come back together at the end of the day.

In rare cases where a loved one dies, the brain is able to consult our memories of being at the bedside or getting the terrible phone call, but those two streams of information conflict for a long time. This leads people to say things like "I'm not crazy" I know they have died, but it really feels like they are going to walk through the door again.

What is going on in the brain when a loved one dies? They know it's irrational, but it's real for them. Many people will believe in an afterlife, but as a neuroscientist, I think the brain is a prediction machine. The heart pumps blood around your body. Your brain can predict what is about to happen so you can prepare. We are always living in our predicted world because of this. We live in two worlds at the same time, our predicted world and the real world, and in some circumstances, those don't match up.

It is difficult to rationalise grieving. In many ways, like Daniel Kahneman's Thinking, Fast and Slow, the places that human beings get tripped up are where our brain has biases or it has conflicting information and so we sort of make up the best story we can to make sense of that. We don't think of grief that way because it is so universal.

There is a distinction between grief and grieving. You want to know what it is you are studying. Are you studying the change in the experience over time, or are you studying the moment when grief comes over you like a wave?

Early on, grief is very intense. People want to know when this will end. If you believe that there will be waves of grief when your child dies, then you will be very disappointed and think there is something wrong with you. When you have that awareness that they are gone again and that brings a wave of grief, that doesn't mean you haven't been grieving. You are starting to figure out how to live in the world without this person.

You argue that the five stages of grief model is incomplete and inaccurate. I have a lot of respect for the man. She was the first to suggest that you could talk about grief. She wrote On Death and Dying in 1969 and the part that was very accurate was when she was describing. The experience that people were relating to her was still true today. Depression, denial, and acceptance are what people experience. She wasn't actually describing grieving but interviewing the same person over a number of times to see the trajectory of what that looked like over time. Although all of those experiences are true, we now know they don't happen in a straight line.

Her interviewing wasn't done in that way, but she presented grieving as a trajectory. Right. In the late 1980s and 1990s, researchers at the University of Michigan interviewed 1,500 people and followed them for 10 years, so they could see how grief develops after a spouse dies. She didn't have access to that kind of data.

Doing things you did with your spouse with a new person is going to cue memories that will probably actually cause grief

People still believe in that model, even though they don't experience that trajectory. I'm not angry, or my stages are in the wrong order.

One reason for buying a child a pet is that they will learn about death, while other parents will protect their children from dying relatives and funerals. Do those things make a difference later in life? Although it looks different from the way adults grieve, it is still important for all of us to have experiences and learn.

We talk about teachable moments. There is a dead bird in the park. What does that mean? How will we feel when we see that? For a pet, who has been a part of the person's life. What rituals do our family engage in? You have a history of how other people have dealt with grief.

It's important to have a view of life that includes death. It could be a religious view or a spiritual view. People who have that tend to do better when it comes to the death of a loved one.

Is the way we grieve influenced by the shift from gravestones to cremations? I think this is fascinating. Where our loved ones are is important to us. Most religions have an answer to those questions. When will you see them next?

Having a location and times when you could visit them helps solve some of the searching that continues.

We have remains even after cremation. Many people have urns in their home, and in many cultures there are altars in the home where people can drop off food or have a conversation. I think to the degree that those are helpful to people, to have that when and where, I think it's useful regardless of how we go about it.

You write a lot about your grief after the deaths of your parents. Do you think being an expert helped you process their deaths, or are you just as sad as everyone else? I wasn't an expert on grief when my mother died. I was at the beginning. I said in the first session that she died, after someone recommended that I see a counsellor. I have written a whole book after 20 years.

When my father died, I had more knowledge about myself, about how to handle grief, and about how we handle reactions. This is not a psychological term, but it was cleaner with my father. It was difficult and painful, but it didn't stick, because it was just grief. It was something I could tolerate and experience.

Many people feel guilty about moving on from a relationship. Absolutely. After my mother died, my father took his wedding ring off and the neighbours were upset. We told him to take care of her in the last year of her life. This is where you are. This is who you are now. No one else has the right to commentary on that.

It is a challenge to move on. We have been in this relationship for a long time and have merged with another person. You won't replace that, and you won't even develop it for quite some time, but doing things that you might have done with your spouse with a new person is going to cause grief. I understand why it's hard to connect again.

Should the family move home to get some new interests? There are people who do that. No matter where you are, you carry that person's absence. They come along with you, so it may be more about recognizing this new person. This is going to be different. I tell the story in the book of an older gentleman who had married his high school sweetheart and had the white picket fence and two children and the dog, and he nursed her through breast cancer and her death. He got teary eyed as he told me about the woman he has been spending time with and she is different. She brings out aspects of him that he forgot, maybe even before high school. He says that it was good then and it is now. I think it's about getting both and finding a way to accept both. Both, and not.

• The Grieving Brain: The Surprising Science of How We Learn from Love and Loss is a book. You can support the Guardian and Observer by ordering your copy at guardianbookshop.com. Delivery charges may apply.