Our minds can 'see' a number of ducks up to a certain number (it depends on how they're arranged, but we might instantly recognise some number of haphazardly-arranged ducks between say three and ten; some savants can recognise many more like the character of Raymond in Rain Man). But after some instantly-recognisable number, we have to execute process to count them.
One of the interesting things about number, Di, is that it's culturally-independent. Our representation of number isn't, but the idea and quantity of number is. Regardless of language, number has developed independently across virtually every culture on earth. A few groups only count up to a certain number and stop, but across those numbers everyone agrees. It's remarkable that we can barter without even a language in common.
So, no, we're not all trained to see five ducks. The only people who disagree about five ducks are those who can't execute a reliable counting-process or refuse to do so.