When children die in hot cars, it is usually because their caregiver forgot they were there. It sounds shocking and unbelievable, but there is actually a scientific reason behind these tragic slips of mind.

Over 900 U.S. children have died in hot cars since 1990. Each year, an average of 38 kids lose their lives after being left in a vehicle. 25 children have died in a hot car so far this year. Just within the past week, four children have suffered this fate. In all four cases, the children were forgotten by their caregivers.

As the death toll rises, organizations, parents, government officials, and scientific experts have been searching for ways to prevent future tragedies. An explanation for how a loving parent could completely forget one of their most cherished family members is an important step in the process. As it turns out, there is one.

READ MORE: Father Tries to Grasp How He Could Have Left Twins To Die In Hot Car

Our brains have two memory systems. With one function, we operate by habit. Turning the coffee on and jumping in the shower in the morning is an example of this autopilot like mindset. Our other memory system helps us remember things out of the norm of our daily routine. Remembering that today is our mother's birthday and calling or sending flowers is an example of this mindset.

When we are not eating properly, sleeping enough, or under extreme stress, we default to operating by habit. If our mental systems are overloaded, our body jumps into autopilot so that our brains can recover from the strain they have been under.

New parents are chronically sleep-deprived and generally operating under an overload of stress. The mental systems that help us remember things that veer from our usual schedule often shut down. Sadly, this explains how a loving parent could drive to work and go into the office, instead of stopping to drop a baby off at daycare when he is first starting.

Lawmakers are fighting for vehicles to have built-in reminders, but they are not getting their bills passed. The best thing you can do for now is always leave your purse or phone in the back seat with your baby. Alternatively, look in the back seat every time you leave your car, even if you're sure your baby is not there.

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