There appears to be an inconsistency in Markman & Dietrich (1998, paras. 67 vs 68): If there is nothing more to being a representation than being a state that mediates between mental contents, why is content still characterized as an open question? A process by which mental contents are related has no need for mental content over and above the terms it relates.
2. The procedural view of memory stresses the consistency between the subject's processing activities when witnessing an event and when remembering it (e.g. Kolers & Roediger, 1984; Morris et al., 1977; Roediger et al., 1989). The emphasis on consistency could have been useful in arguing for mediation. (Markman & Makin (in press) also invoke "consistency" in their work on similarity and categorization; see also Goldstone & Barsalou 1996.) Consistency may also bear on the role of surface features in problem solving (e.g. Holyoak & Spellman, 1993). This work not only provides additional support for Markman & Dietrich's general view of representation (more on mediation, please!), but their conclusion would also have benefited from it.
3. The relationships between different subject-environment interactions suggest there may be no further question to answer about the content of representation. The target article is not very clear about this, as its conclusion demonstrates. The foregoing references could have strengthened what was probably Markman & Dietrich's most important argument (section D, para. 67): "[T]here is nothing more to being a representation than being a mediating state. Mediating states not only constitute the general class to which more specific kinds of representations belong; they capture the essence of representation ." True mediational models can be found in the Koriat & Goldsmith review (1996), but instead of citing them, Markman & Dietrich counter their argument (that there is nothing more to being a representation than being a mediating state) in the immediately succeeding paragraph: " We hasten to add, however, that crucial questions about representations still remain. Chief among them is the way that representations get their content" (section D, para. 68).
4. Does this last question about content need to be posed at all? Insofar as a representation is defined as a relationship between different mental contents, I suspect that Markman & Dietrich do not really want to insist that it has content. Assuming that I am not distorting what they mean by mediation, this further property appears unnecessary.
5. This point can be highlighted with an example adapted from Searle (1995): if I see A, and if A resembles B, then I will have the tendency to form an image of B. In this case, the process by which I go from the perception of A to the image of B does not imply some additional mental content. The principle which is supposed to explain the functioning of the system, namely, a similarity process, does not imply any supplementary content at all. Specifically, the similarity process does not imply that when I see A and when I remember B, I am using a rule such as 'If I see A and if A resembles B, then I should think of B'.
6. In summary, a process by which mental contents are related has no need for mental content over and above the terms it relates. If there is nothing more to being a representation than being a state that mediates between mental contents, why is the question of content still described as open?
Kolers, P.A. & Roediger, H.L. (1984). Procedures of the mind. Journal of Verbal Learning and Verbal Behavior, 23, 425-449.
Koriat, A. & Goldsmith, M. (1996). Memory metaphors and the real-life/laboratory controversy: correspondence versus storehouse conceptions of memory. Behavioral and Brain Sciences, 19, 167-188. ftp://ftp.princeton.edu/pub/harnad/BBS/.WWW/bbs.koriat.html
Markman, A.B. & Dietrich, E. (1998) In Defense of Representation as Mediation. PSYCOLOQUY 9 (48) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/1998.volume.9/psyc.98.9.48.representation-mediation.1.markman
Markman, A.B. & Makin, V.S. (in press). Referential communication and category acquisition. Journal of Experimental Psychology: General.
Morris, C.D., Bransford, J.D. & Franks, J.J. (1977). Level of processing versus transfer-appropriate processing. Journal of Verbal Learning and Verbal Behavior, 16, 519-533.
Goldstone, R.L. & Barsalou, L.W. (1996). Reuniting perception and conception: The perceptual bases of similarity and rules. Indiana Cognitive Science Program, Research report 159, Indiana University, Bloomington.
Holyoak, K.J., Spellman, B.A. (1993). Thinking. Annual Review of Psychology, 44, 265-315.
Searle, J.R. (1995). La redecouverte de l'esprit. Paris: Gallimard (The rediscovery of the mind, 1992, MIT Press).