Kruger and dunning (1999) found that those students who scored lowest on tests of grammar and logic were to overestimating their abilities. most prone sometimes prone least prone

I believe the answer is: Most prone

People that scored the lowest on such tests often make themselves think that they could easily pass it without making additional effort as a form of justification to avoid The feeling of failure. Often times, this also make them overestimate their ability and not making extra effort which lead to another failure in the future.