We are more likely to com­ply with requests from strangers if we believe we share seem­ingly uncom­mon, inci­den­tal char­ac­ter­is­tics (e.g. first name, birth­day, etc.), accord­ing to a 2004 research study pub­lished in the Per­son­al­ity and Social Psy­chol­ogy Bul­letin (pdf):

Four stud­ies exam­ined the effect of an inci­den­tal sim­i­lar­ity on com­pli­ance to a request. Under­grad­u­ates who believed they shared a birth­day (Study 1), a first name (Study 2), or fin­ger­print sim­i­lar­i­ties (Study 3) with a requester were more likely to com­ply with a request than par­tic­i­pants who did not per­ceive an inci­den­tal sim­i­lar­ity with the requester. The find­ings are con­sis­tent with past research demon­strat­ing that peo­ple often rely on heuris­tic pro­cess­ing when respond­ing to requests and with Hei­der’s descrip­tion of unit rela­tion­ships in which per­ceived sim­i­lar­i­ties lead to pos­i­tive affect. Con­sis­tent with the unit rela­tion inter­pre­ta­tion, par­tic­i­pants did not increase com­pli­ance when hear­ing about an inci­den­tal sim­i­lar­ity with some­one other than the requester or when they believed the fea­ture they shared with the requester was common.

Won­der­ing why there were two birthday-related posts today? Today I am 25!