Question

In an experiment by zentall and morris (2010), children who received which of these examples of praise would feel most motivated to draw again in the future?

Answer 1

I believe the answer is: "You really worked hard!"

According to their conclusion, giving such praise would make the children feel that all of their effort is being valued/acknowledged.
This would make them more likely to seek those positive affirmation by repeating the same action again in the future.