Willard wrote:
The phrase 'can't walk and chew gum at the same time' is an old slang expression, indicating someone who is extremely stupid.
I don't think it was ever intended to describe anything that was an actual feat of coordination, as it represents something so simple even an idiot can do it without conscious effort.
that was needlessly mean. there ARE folk who have trouble with this task, including myself, who has always been clumsier than average. because i am a mouthbreather [chronic sinus troubles] i often find that chewing on something while walking IS a challenge.