Simplify the following text for a Grade 11 native English-speaking person.
Original: C.D. Fisher said that psychologically , boredom is â an unpleasant , transient ( changing , not lasting ) affective state in which the individual feels a pervasive ( thorough ) lack ( not having ) of interest in and difficulty concentrating on the current ( present , happening now ) activity .
Simplified: Boredom has been defined by C. D. Fisher in terms of its central psychological processes : â an unpleasant , transient affective state in which the individual feels a pervasive lack of interest in and difficulty concentrating on the current activity .