Of course, forgetting a child is far different from forgetting a gallon of 2%. But not to the reptilian brain. Imagine that your plan is "Drop kid at babysitter's on the way to work." If you're tired or distracted by worries, or -- worse -- if you're not the person who usually takes the kid to the sitter's, your habit system can erase that plan with appalling ease. Like Mary Parks, you go straight to work on auto-pilot, spacing out on the fact that your child is with you in the backseat. You even develop false memories of dropping him off. "The brain is very good at filling in gaps, so you will remember what you assume you did," Diamond says.
Ironically, hot-car deaths have become much more common thanks to practices meant to protect young passengers: placing them in the backseat and positioning infant seats to face backward. These precautions, which became standard in the 1990s, are important to follow because they shield babies and small kids from airbags and other hazards. But they can also put them "out of sight, out of mind."
Diamond knows this first-hand. One day last year, he forgot that his baby granddaughter was in the car with him during a drive to the mall. (She normally would not have been.) "I could have walked around that mall for hours, having absolutely no recollection that she was in the car," Diamond says. Fortunately, his wife was with him, too, and remembered to get the baby out. Experts suspect there are thousands of such "almosts" each year. But few of those stories become public -- making it easier for the rest of us to jump to damning conclusions when tragedies like Parks's hit the news.