"The case in New Zealand is consistent with the pattern I have seen in many dozens of other cases.
"It appears that the mother did not normally take the child to day care... and so the mother was now trying to do something out of her ordinary routine."
Forgotten Baby Syndrome was not a mental disorder, but occurred when people tried to interrupt their regular routines.
A brain memory system allowed people to engage in routine behaviour without thinking about it.
"So you can drive straight home from work you don't even have to think about it you just go along that route. It is your brain habit system that allows you to do that."
However, he said there was another brain memory system that tried to interrupt the brain habit system, while processing new information.
"The problem is that the habit system can out compete the new memory brain system and that's what happens in this case - that we do something out of habit and the brain memory system for a habit is actually suppressing the system that's trying to interrupt the habit.
"In this particular case what you have is a prime example of where the woman's habit system took control and basically took her from home to work."
Prof Diamond said the woman's brain would have also created a "false memory".
"That's how she's able to go for hours at a time at work and not think about the child because her brain has created this false memory that her child must be at daycare.
"Your brain deceives you into believing you have done what you intended to do."
He said Forgotten Baby Syndrome was "extremely rare", with 25 children dying around the world each year as a result of the phenomenon, however there were also many un-reported cases of the syndrome occurring, where parents have quickly realised they have left their children.
"We have many near misses in which kids have been forgotten in cars and children did not die."
He said in his opinion, it was difficult to prosecute parents who had suffered from Forgotten Baby Syndrome.
"There is absolutely no evidence of malice, there is no evidence these parents wanted to cause any harm to these children and nothing will be gained from society to put these people in prison.
"The activity of leaving a child in a car does not reach the threshold for an action that actually deserves to be prosecuted, because there is no awareness the action can cause harm."