Daddy, is this true? If there were giants, then a football to them would be the same size as a pea to us.
That was, word for word, a completely out-of-the blue utterance by our 6 year old daughter, Lillian.
Her “if…then” construct is what is known as a counter-factual conditional – If [something that is not in fact true] then [something else that is not in fact true], and to correctly construct such conditionals you use subjunctive verb forms (were… would be…).
I’m amazed that somehow, without any explicit instruction at all, Lillian can spontaneously express counterfactual conditionals with perfectly grammatical sentences of complex construction. (In saying this, I’m not implying that I think Lillian is somehow especially advanced. I assume she’s showing a normal developmental progression. It is that progression which is amazing.)
But what really amazes me is that somehow, without instruction, she’s acquired the conceptual capacity to talk about the truth value of counterfactual conditions. (Aside: in some of our workshops we teach professionals such as intelligence analysts to try to avoid talking (i.e. thinking) about truth of conditionals, where there are regular alternatives, since it is so much more cognitively demanding than thinking about regular statements.)
No wonder linguists have argued that humans have a kind of innate capacity for language acquisition.
[repost of a shorter version posted on another blog]