Claire Bombardier, the University of Toronto researcher who had conducted Merck's big ulcer study, criticized the new studies for not being placebo-controlled.

FORBES: Behind Merck's Fall

On the other hand, mothers who engaged in negative gatekeeping, grimacing or criticized fathers' efforts to take charge, could block out even fathers who believe they should be involved, says the study, led by Sarah Schoppe-Sullivan, assistant professor, child development, at Ohio State University.

WSJ: Managing Your Re-Entry to the Work Force After Child Rearing