[aliveupstairs]

> Number of studies.

Source your claims (at least one.)

I very much doubt this because only recently has it been possible for parents of the same sex to adopt, let alone evaluate their performance as parents and generalise it. I would very much love to be proven wrong, however.

That being said, the issue here is not the gender of the parent, but rather single parenthood. A working single parent interacts very much little with their kid(s) in comparison with an atomic family.