New, unwanted task bar behavior.

My task bar is exibiting a new behavior. Formerly, when mousing over a running app on the bar, I small cameo would popup. Now if I mouse over the app is maximizes. That is anoying and clutters my desktop with apps I have minimised to clear my work area. How do I set that back to it's former behavior?

The new behavior seemed to begin about a week ago with no changes on my part. Curious as I have postponed the latest update for longer than that time. To my knowlege, no update was performed.