Mental extrapolation and cognitive penetrability: reply to Ranney and proposals for evaluative criteria.

We propose three criteria for establishing that mentally extrapolated motions are impenetrable with respect to one's knowledge, beliefs, or expectations about the nature of corresponding physical motions, and we review recent findings on mental extrapolation and representational momentum that appear to meet these criteria. We also respond to some arguments recently proposed by Ranney (1989) and Hubbard and Bharucha (1988) that representational momentum is cognitively penetrable. We conclude that mental extrapolations are governed to at least some extent by the inherent properties of the underlying internal mechanisms.