The Mincome experiment in Canada didn't really show the result you're talking about:
The results showed a modest impact on labor markets, with working hours dropping one percent for men, three percent for married women, and five percent for unmarried women.
These decreases in hours worked may be seen as offset by the opportunity cost of more time for family and education. Mothers spent more time rearing newborns, and the educational impacts are regarded as a success. Students in these families showed higher test scores and lower dropout rates. There was also an increase in adults continuing education.
(References from http://en.wikipedia.org/wiki/Mincome)
So, basically, mothers worked less, and kids who should have been in school worked less (and educated themselves more), and everyone else worked the same amount.