a thought: animals spend most of their time foraging, while humans spend most of their time working, allegedly so that they can indirectly forage (buying food with money), but also so that they can be seen from their peers that they forage, as idleness is taboo. An evolution leftover? How about leisure & free time management in primates? Precious little can be found online on this.

Somewhat related research: http://www.cambridge.org/catalogue/catalog...isbn=0521858372
http://www.unisci.com/stories/20021/0218021.htm