The ACE, as planned, would have at most 200,000 digits in store.
He described the storage planned for the ACE as 'comparable with the memory capacity of a minnow'.
But even so, he perceived the development of 'learning' programs as something that would be feasible within a short period: not merely a hypothetical possibility, but affecting current research in a practical way.
On 20 November 1946 he had replied to an enquiry from W. Ross Ashby, a neurologist eager to make progress with mechanical models of cerebral function, in the following terms:
The ace will be used, as you suggest, in the first instance in an entirely disciplined manner, similar to the action of the lower centres, although the reflexes will be extremely complicated.
The disciplined action carries with it the disagreeable feature, which you mentioned, that it will be entirely uncritical when anything goes wrong.
It will also be necessarily devoid of anything that could be called originality.
There is, however, no reason why the machine should always be used in such a manner: there is nothing in its construction which obliges us to do so.
It would be quite possible for the machine to try out variations of behaviour and accept or reject them in the manner you describe and I have been hoping to make the machine do this.
This is possible because, without altering the design of the machine itself, it can, in theory at any rate, be used as a model of any other machine, by making it remember a suitable set of instructions.
The ace is in fact, analogous to the 'universal machine' described in my paper on computable numbers.
This theoretical possibility is attainable in practice, in all reasonable cases, at worst at the expense of operating slightly slower than a machine specially designed for the purpose in question.
Thus, although the brain may in fact operate by changing its neuron circuits by the growth of axons and dendrites, we could nevertheless make a model, within the ace, in which this possibility was allowed for, but in which the actual construction of the ace did not alter, but only the remembered data, describing the mode of behaviour applicable at any time.
I feel that you would be well advised to take advantage of this principle, and do your experiments on the ace, instead of building a special machine.