Sharks electrically detect things to eat and things that impede locomotion (Kalmijn, 1974). An edible living thing such as a flatfish differs in ionic com• position from the surrounding water, producing a bioelectric field partially modulated in the rhythm of the living thing's respiratory movements. A flatfish that has buried itself in the sand will be detectable by a shark swimming just above it. Reproducing the bioelectric field of the flatfish artificially, bypassing a current between two electrodes buried in the sand, invites the same predatory behavior. The shark digs tenaciously at the source of the field departing from the site when the act fails to reveal an edible thing (Kalmijn, 1971). Now there is no intelligible sense in which it can be claimed that the source ought to have appeared inedible if the shark's perception were free of error and if the shark's perception of affordances were direct. In the niche of the shark 'an edible thing' and 'electric field of, say, type F' are nomically related. To predicate of the shark (a) 'detects electric field of type F' and (b) 'takes to be an edible thing' is not to refer to two different states of affairs, one (viz. (b)) that is reached from the other (viz. (a)) by an inference. Rather, it is to make reference in two ways to a single state of affairs of the shark-niche system. The linking of (a) and (b) is not something that goes on in the "mind" of the shark, as the Establishment would have it. The linking of (a) and (b) is in the physics of an ecological world, namely, that system given by the complementation of the shark and its niche.Consider, now, the final paragraph. TSRM note (correctly, I believe) that we would not say that the actions are mistaken in the non-standard environments. I think the shark's actions are appropriate given that it takes there to be an edible thing. But, if it takes things to be that way, then it's taking things to be some way that they are not. That is, what it takes to be true is, in fact, false. But, false takings are a problem for the EP approach.
But what of the shark's actions? Should we not classify them as being in error, as being wrong? After all, the source of the electric field proved not to be an edible thing. Given the nomic relation between 'electric field of type F' and 'edible' there is no intelligible sense in which it can be said that the shark's act of investigating the source of the field was wrong. The wrong action for the shark, given its niche and its appetite, would be not investigating the source of the field. (Turvey, Shaw, Reed, & Mace, 1981, pp. 276-7).
TSRM might claim that, in the non-standard environment, the shark does not take there to something edible. But, that would conflict with their claim that (a) and (b) are the same state of affairs.