That is seeming to purposefully do something they know they shouldn't.

I think as soon as my LO could crawl she started being slightly naughty - she'd crawl for the electric outlets (they were covered but I still didn't want her playing with them) as soon as I walked away.

Now at 14 months I know when she's about to be naughty because she stops and looks at me first.

I feel like she's torn between her curiosity and knowing mommy disapproves. I'm surprised at how early it starts.