pSlide 1p pPsychological principlesp p: : : 500 :42740 1436-1437p p:p p1- 2- 3- 4- 5- 6- 7- p p p p p p8p pp p!p pInterest p pp p:p p12p pNeed p pp pp pp p p p Piagetp p- - - - - p pp pnull12314543p