▁writer ▁of ▁children ' s ▁poetry ▁and ▁his ▁mat ernal ▁grand father ▁on ▁the ▁editor ▁of ▁the ▁Chicago ▁Trib une . ▁ ▁Ald is ▁taught ▁econom ics ▁at ▁Y ale ▁University ▁and ▁worked ▁in ▁invest ment ▁in ▁New ▁York . ▁But ▁in ▁the ▁ 1 9 5 0 s ▁he ▁moved ▁west ▁to ▁San ▁Francisco ' s ▁Bay ▁Area ▁and ▁began ▁to ▁develop ▁his ▁academic ▁interest ▁in ▁behavior al ▁psych ology . ▁He ▁is ▁most ▁noted ▁for ▁his ▁well ▁received ▁ 1 9 7 1 ▁publication ▁Play ▁Fight ing ▁which ▁is ▁an ▁eth ological ▁classic ▁exam ining ▁play ▁in ▁humans ▁and ▁animals . ▁The ▁study ▁was ▁based ▁on ▁extensive ▁observ ational ▁studies : ▁ 1 , 5 0 0 ▁hours ▁of ▁field ▁observation ▁on ▁humans , ▁ 7 0 0 ▁hours ▁of ▁observations ▁on ▁animals ▁at ▁four ▁California ▁zo os ▁and ▁more ▁than ▁twenty ▁hours ▁of ▁fil med ▁playing ▁humans ▁and ▁various ▁animals . ▁ ▁He ▁was ▁a ▁member ▁of ▁the ▁International ▁Society ▁for ▁Human ▁Eth ology . ▁ ▁Selected ▁publications ▁ ▁Ald is , O wen ▁( 1 9 7 5 ) ▁Play ▁Fight ing , ▁Academ ic ▁Press , ▁New ▁York , ▁▁ ▁Ald is , O wen ▁( 1 9 6 1 ) ▁Of ▁P ige ons ▁and ▁Men . ▁Harvard ▁Business ▁Review , ▁ 3 9 ( 4 ), ▁ 5 9 - 6 3 . ▁ ▁References ▁▁ ▁Category : 1 9 2 6 ▁birth s ▁Category : 2 0 0 1 ▁death s ▁Category : American ▁psych