The ease with which images, events and concepts come to mind is correlated with how frequently they have been observed, which in turn is correlated with how likely they are to happen again.

Yes, and I was trying to make this description one level more concrete.

Things never happen the exact same way twice. The way that past observations are correlated with what may happen again is complicated - in a way, that's exactly what "concepts" capture.

So we don't just recall something that happened and predict that it will happen again. Rather, we compose a prediction based on an integration of bits and patches from past experiences. Recalling these bits and patches as relevant for the context of the prediction - and of each other - is a complicated task, and I propose that an "internal availability" mechanism is needed to perform it.