What are the causes of mass delusion? Conformity? Pluralistic ignorance? (everybody seems sincere in their convictions it must just be me!) Illusions of unanimity? Illusions of invulnerability? Direct pressure on any member who questions the group to conform - disloyalty! The list goes on... I have read that mass delusion occurs with severe group-think... O.K. I have a simply question - see the photo I have provided below (the file rectangles.JPG). Now can anybody on the entirety of the physics forum measure the rectangle on the right to be half the size in every regard of the rectangle on the left? (measured directly straight from the photo?): rectangles.JPG It is just that I have a group of people telling me they are sure the rectangle on the right is half the size of the rectangle on the left. Trouble is I cant measure it to be half the size and neither can the several other people I have asked!!! In fact one of them burst out laughing when I told him that THEY think that that is half the size of that. Despite this there is this GROUP who INSISTS it is half the size nevertheless...I'm thinking that if they are being serious that this is a case of mass delusion... Do any of you people get it to be half the size????