From the mid- to late 1960s, Brian Lewis, Bernard Scott, and I conjectured that learning strategies, teaching strategies, and even plans of action have characteristic types which can be differentiated (Lewis & Pask, 1964, 1965; Pask, 1961, 1970, 1972; Pask & Lewis, 1968; Pask & Scott, 1971, 1972, 1973). Individual difference psychologies have maintained a similar stance and with greater precision regarding the nature of strategies. An overview of the approach taken by my own group in the 1960s is described in the remainder of this section. Learning and teaching strategies can, under appropriate circumstances, be substantially exteriorized or externalized for observation. Protocols can serve this purpose, but we used maplike representations of what may be known or learned. These representations were open to continuous evolution as further topics and relations between them were added by learners.