I think what you are missing is that ducklings "attach" to the first thing they see after birth and follow it around. Under normal conditions this would be thei

I think what you are missing is that ducklings "attach" to the first thing they see after birth and follow it around. Under normal conditions this would be their parent, which is desirable as it keeps them out of trouble. (As an amusing aside, a similar imprinting is used in some security mechanisms, where the device allows the first use without authentication, but then trusts the first user to be the privileged user). The important bit is that this is not "training", but a single stimulus that they need to figure out who mom is. But it turns out that mom can be also abstract things, like "similarity". Now if you compare this to a neural net, you can't get it to recognise anything after showing just 1 image, let alone the notion of similarity.