IT'S agonising to think about. A baby boy approaching his first birthday died after being left in a car found in front of a daycare centre in Helena Valley, Western Australia at 4pm on Wednesday.

Police are still investigating, but say they they are not treating the death as suspicious, but as a tragic accident.

It is understood the boy's father arrived at the childcare centre to pick up his son, but staff told him his child had never been dropped off. The shocked father returned to his vehicle, where he found the unresponsive boy in the backseat of the car.

But how does an incident like this happen?

Internationally there is a tragic record of deaths where parents have, at the end of a horrifying sprint to the car, found their child dead.

Writer Gene Weingarten won a Pulitzer Prize for a Washington Post investigation which found 15 to 25 children die each year in the United States after being left in cars. One horrible day in America it happened to three babies.

Weingarten chronicles how ordinary people simply forget they have their baby in the car and go about their ordinary lives, leaving their child in the car, not through neglect but believing they have been dropped at day care, or with a nanny or into the loving arms of a relative.

It is easy to jump to conclusions about the character of the parent. But Weingarten's explanation of who is responsible will surprise you.

"The wealthy do (it), it turns out. And the poor, and the middle class. Parents of all ages and ethnicities do it. Mothers are just as likely to do it as fathers.

"It happens to the chronically absent-minded and to the fanatically organised, to the college-educated and to the marginally literate.

"In the last 10 years, it has happened to a dentist. A postal clerk. A social worker. A police officer. An accountant. A soldier. A paralegal. An electrician. A Protestant clergyman. A (Rabbi) student. A nurse. A construction worker. An assistant principal. It happened to a mental health counsellor, a college professor and a pizza chef. It happened to a pediatrician. It happened to a rocket scientist."

Weingarten continued: "Several people have driven from work to collect the child they thought they'd dropped off, never noticing the corpse in the back seat.".

Just last month, a Texas family found baby Lillian Isabel Guerra dead in the back seat of the car. Her father forgot to take her to childcare after dropping his other children at school.

A similar catastrophe happened to Elena Petrizzi, just shy of two years of age. Her father, Lucio, found her unconscious in the back of his hot car in 2011. He was convinced he had dropped her off.

How something like this happens differs from case to case. A reason that is commonly cited has to do with the human psyche and brain function.

Psychologist Michael Carr Gregg says people often operate day-to-day in a "state of flow". That means they are carrying out a routine task on autopilot while focusing on other things.

While the infant deaths are extreme examples of this, many of us have experienced moments of absent mindedness like this.

"I once had a very similar experience where I put my child safety seat on the top of the car roof," Mr Gregg said. "The child wasn't in it, but I drove off with the bloody thing on top."

"I had no memory at all of not putting it in the back seat."

Your brain's autopilot is called the basal ganglia. While the more complex brain structures that carry out higher-level thought are elsewhere - say planning your evening - your basal ganglia is running the routine motor skills required to drive you home from work.

But molecular physiology professor David Diamond told The Washington Post that when a person is stressed, sometimes the more primitive basal ganglia can take over.

"The important factors that keep showing up involve a combination of stress, emotion, lack of sleep and change in routine," he said. That makes a person's conscious mind too weak to do its job.

Although police do not know the exact cause of the child's death in Western Australia, the early response from police and the day care centre was that it had been a tragic accident.

Daycare staff performed CPR on the boy but their desperate attempts to revive him were unsuccessful. They have been offered counselling following the tragedy.

General Manager of the daycare centre Kim Beange praised the professionalism of the centre's workers and assured parents that no other children were aware of the incident.

"Our thoughts and condolences are with the parents of the child and their family through this tragic time."

Earlier, a police spokesman said: "It is a tragic time for their family and it's also hard for the daycare centre staff, who were also present."

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