The same task triggers different levels of awareness of one' s surroundings, called environmental awareness, in different individuals  Mathematical puzzles, for example, cause most people to increase such an awareness  Some people -- those who formulate the answer visually, imagining the numbers in their mind' s eye -- will, in an attempt to freeze the picture, experience a decrease in environmental awareness while solving the puzzle
Other people' s environmental awareness may rise during the exercise, because their brains are signaling a rest at the end of every stage of problem solving
There are some people for whom mathematical puzzles do not cause an increase in their level of environmental awareness.