It is a mistake to imagine that providing for mental engagement is, in itself, enough to ensure that understanding will follow. The various strategies which foster understanding may provide a gentle slope up to one significant hurdle but there are others to cross. For instance, the learner must be willing to make an inference. There is sometimes a tendency to ignore such hurdles. For instance, Petraglio (1998) describes how constructivist education has tended to base its thinking on the assumption that all students are bright-eyed, bushy-tailed, enthusiastic learners. Of course, as teachers are only too aware, such an oversight can reduce any lesson to chaos, constructivist or not. In practice, each of us has a variety of attitudes, motives, emotions and other attributes which affect what we do. For example, the adverse effects of learner anxiety on achievement and on teachers’ judgements about the learner have been known for some time (for example, Grossman, 1969). Far from being like sparkling shopping trolleys just waiting to be filled with goods, we have those that are reluctant to start, difficult to steer, and full of boxes that resist the intrusion of more, even when they have been carefully shaped to fit. What people actually do about their learning is not completely determined by what we do to make it easier. Learning behaviour is shaped by the total mental environment and, like an iceberg, a lot of it is out of sight (Lewin, 1938).