This is a thought provoking examination of the topic.

There is also a case to be made that most babies (at least for English speakers) will say 'dad/daddy' before 'mum/mummy' because 'd' is easier to say than 'm' so they can form that sound earlier. We should also try not to over think things around favouritism because no matter how much care you take to avoid it everyone is different and each child needs different levels of guidance, so they will always see favouritism whether it's there or not.