Fathers' brains respond differently to daughters than sons. Fathers with toddler daughters are more attentive and responsive to those daughters' needs than fathers with toddler sons are to the needs of those sons, according to brain scans and recordings of the parents' daily interactions with their kids. Ref. Source 6f.
I have to disagree some what about this study. I was no more attentive to my daughters than my step sons. I treated them all as equals in everything they did. I may be the odd ball. I think that sons and daughters being raised up as equals in all they do helps show them they are safe and protected no matter their gender.