Staph bacteria. Picture courtesy of Janice Carr/CDC via BBC.

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Do bacteria have representational beliefs?

Schwitzgebel (2003) cites a case (taken from Dretske, 1988) which may suggest that certain bacteria are capable of forming representations of their environment, if we view representational systems as systems that track features of their environment. For philosophers who adopt a representationalist account of belief, this raises the question of whether bacteria are capable of having beliefs. The bacteria in question have compartments called magnetosomes, which contain particles of magnetite.

Organisms, especially mobile ones, generally need to keep track of features of their environment to be evolutionarily successful. Consequently, they generally possess internal systems whose function it is to covary in certain ways with the environment. For example, certain marine bacteria contain internal magnets that align with the Earth's magnetic field. In the northern hemisphere, these bacteria, guided by the magnets, propel themselves toward magnetic north. Since in the northern hemisphere magnetic north tends downward, they are thus carried toward deeper water and sediment, and away from toxic, oxygen-rich surface water. We might thus say that the magnetic system of these bacteria is a representational system that functions to indicate the direction of benign or oxygen-poor environments (Schwitzgebel, 2003).

But are the bacteria representing anything here? Procyshyn (2001) argues that they are not. A representational account has to do some extra explanatory work that a purely causal account cannot; otherwise it is redundant. An example from Procyshyn illustrates why: when someone taps my bent knee with a mallet, a neural pathway fires, causing my leg to jerk and straighten - a reflex process over which I have no control. Now, we could say that the external stimulus (mallet) is represented by my neural pathway, and that the function of this representation of to straighten my leg. Or we could explain the reflex in purely causal terms. Given that both accounts describe what goes on equally well, we should prefer the simpler, causal account.

Fred Dretske. Photo courtesy of Stanford University.

Following Dretske, Procyshyn then proposes that "a representation's function is to supplement a causal chain of events" (2001, p. 134, italics mine) and that "the function of a representation is to encode, use or deliver information about the external world that is pertinent to the representing organism's survival" (2001, p. 134). Since, for these bacteria, the downward direction of the benign environment correlates with the direction of magnetic north detected by the bacteria's sensors, we can say that an external state of affairs is correlated with an internal state of the bacteria, whose biological function is to use, encode or deliver information to the bacteria that assists in their survival. Thus Dretske considers that the bacteria have a genuine representational capacity (although, like most representationalists, he does not credit them with beliefs).

But as Dretske points out, if we hold a bar magnet over these bacteria, they align themselves with the magnet, not with magnetic north. What the bacteria are doing is aligning themselves with the nearest magnet. Procyshyn comments:

...[G]iven the manner in which the magnetosome represents, it is incapable of misrepresenting. Since the magnetosome appears to represent magnetic north proximally, there is no way for the magnetotactic sensor to misrepresent. No malfunction is possible here (2001, p. 135).

Procyshyn argues that a representation, by definition, is something that can be right or wrong, true or false. If the bacteria are not capable of mis-representing, then we should not speak of them as representing either. And if they cannot be said to represent, then the question of bacterial beliefs does not arise.

N.9 A necessary condition for the ascription of beliefs to an organism is that it be capable of mis-representing events occurring in its surroundings.

Bacteria, like all other organisms (except viruses) are certainly capable of encoding a variety of information about their environment. However, we need to be careful not to describe their capacities in philosophically inappropriate ways, thereby generating pseudo-problems.

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