A common misconception among the courts is that infants cannot be with their fathers, and in fact should be exclusively with the mother at night.  There is little, if any evidence for this proposition and in fact only serves to underscore the inherent prejudice fathers experience in California courts.  Social workers and psychologists unfamiliar with even the most basic research nonentheless make life-changing decisions in favor of mothers and against fathers.  According to Joan Kelly, a foremost expert in child development:

There is absolutely no evidence that children’s psychological adjustment or the relationships between children and their parents are harmed when children spend overnight periods with their other parents. An often mis-cited study by Solomon (1997) reported high levels of insecure infant-mother and infant-father attachment when parents lived apart, although toddlers who spent overnights with both their fathers and mothers were not significantly more likely to have insecure relationships than those children who did not have overnights visits with both parents.”

http://www.deltabravo.net/custody/overnights.php