In 1973, Lepper and colleagues conducted an experiment in which children did drawings. Some of the children were promised a reward while others received a surprise reward. The researchers found that the children who received the expected reward for drawing .

You did not show us the image of the burger, but i shall try to answer as best i can.  when purchasing food, always consider the ingredients as well as the person who prepared it. consider if they were hygienic people or not, in case the burger was infected with bacteria. no mortal should place an infected burger into their mouth.