What is the middle category bias in rating scales?

The correct answer is Option 3: Placing individuals in the middle of the scale

The middle category bias refers to the tendency of raters to place individuals in the middle of the scale by avoiding extreme positions.

Why Option 2 is not the answer?

Both Option 2 and 3 may seem correct, but there is a subtle difference. Option (2) “avoiding extreme positions” describes the behaviour of the rater, while Option (3) “placing individuals in the middle of the scale” describes the actual result of that behaviour. Middle category bias is defined in terms of what ultimately happens in the ratings—most individuals get clustered in the middle category. Therefore, Option (3) is the more precise and complete answer, while Option (2) is only a partial description of the tendency.