Abstract
Finding out why we have beliefs and desires is important for a thorough understanding of the nature of our minds (and those of other animals). It is therefore unsurprising that several accounts have been presented that are meant to answer this question. At least in the philosophical literature, the most widely accepted of these are due to Kim Sterelny and Peter Godfrey-Smith, who argue that beliefs and desires evolved due to their enabling us to be behaviourally flexible in a way that reflexes do not—which, they claim, is beneficial in epistemically complex environments. However, as I try to make clear in this paper, upon closer consideration, this kind of account turns out to be theoretically implausible. In the main, this is because it fails to give due credit to the powers of reflex-driven organisms, which can in fact be just as flexible in their behaviour as ones that are belief/desire-driven. In order to improve on this account, I therefore propose that beliefs and desires evolved, not due to their enabling us to do something completely different from what reflexive organisms can do, but rather due to their enabling us to do the same things better. Specifically, I argue that beliefs and desires evolved for making the generation of behaviour more efficient, since they can simplify the necessary cognitive labour considerably. I end by considering various implications of this account.
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Notes
This clearly assumes that we really do have beliefs and desires. This seems a very reasonable assumption to make (see e.g. Stich 2009a, b; Nichols and Stich 2003); moreover, to the extent that it is still found unpersuasive, the argument presented here can be taken to provide further evidence for its truth (see also Sterelny 2003a, p. 7). Note also that the issue here does not concern the (folk) concepts of ‘belief’ and ‘desire’—rather, it concerns the actual structure of our cognitive architecture.
Note that, with the exception of Sterelny (2003a), nearly all of these accounts concentrate exclusively on beliefs, and leave desires largely unmodelled. For present purposes, though, it is better not to separate these two so drastically.
In behavioural ecology, it is customary to distinguish more finely among reflexes, habits, instincts, fixed actions patterns, drives and a number of other behavioural dispositions (see e.g. Krebs and Davies 1997; Mackintosh 1983, 1994). In the present context, though, making this finer distinction is not necessary.
For more on input and output systems, see e.g. Fodor (1983); for more on an organism’s internal configuration, see Damasio (1994). In both cases, there is much room for debate about exactly what these systems are and how their states are best characterised; for present purposes, though, this can be left open. Note also that the term ‘decision making system’ ought not to be overinterpreted here—in particular, it is not to be seen as referring to any kind of representational system.
Note also that, in some cases, the internal states can by themselves initiate an action (as when the organism stops doing whatever it is doing when it is in pain), and that the same is true for the input states (as when we lower our eyelids upon registering the presence of an object near our retina). For present purposes, though, these complications can be left aside.
For a related (and slightly more detailed) picture, see also Dickinson (1994, p. 54) and Timberlake (2002, pp. 109–110). Note, though, that Dickinson’s view of these matters is fairly complex: he thinks that a reflex-based model can be seen as the realisor of a belief/desire-based one (see e.g. Dickinson 1994; Dickinson and Balleine 2000). A closer discussion of this idea is not possible here, however.
That said, since belief/desire-driven organisms can also retain some reflexes, some input and internal states can initiate behavioural sequences directly even there. See also notes 9 and 22.
Of course, there is much more that could be said about the nature of beliefs and desires; for present purposes, though, the account of the text is sufficient. Note also that this account does not entail that content internalism a la Fodor (1980) is true. In particular, there is no need to assume that the content of our beliefs and desires are our input and internal states.
Note that since a belief/desire-driven organism is likely to maintain some of its reflexes (see also notes 7 and 22), a full picture of the latter kind of architecture would also contain an assembler that feeds some combinations of input- and internal states directly to the decision making system. I have not included this in Fig. 2 so as to make it easier to read. Note also that a combined picture of this sort might be seen to spell out the underpinnings of dual-system architectures like those defended e.g. by Sloman (1996), Stanovich (1999), and Carruthers (2006). I thank an anonymous referee for useful discussion of this point.
Note that precursors of this account can be found in the nineteenth century (see e.g. the work of Spencer and Dewey); however, when it comes to the more specific issue of belief/desire-based vs. reflex-based decision making, Godfrey-Smith (1996) and Sterelny (2003a) clearly do deserve special mention. Note further that, in what follows, I shall concentrate on Sterelny’s (2003a) treatment, as it is a bit more detailed than that of Godfrey-Smith (1996). Finally, note that Sober (1994) presents a model that is formally similar to that in Godfrey-Smith (1996); however, he uses this model in a very different way. In particular, Sober (1994) is interested in determining which kinds of beliefs (variable or fixed) are adaptive under which circumstances, not with why we have beliefs at all; accordingly, his account will not be discussed further in what follows.
For actual examples of these sorts of cases, see Heyes (1994, p. 293) and the references mentioned there.
Note that this usefulness reaches a maximum, and then drops off again: in epistemically closed environments, there is no need to use decoupled representations either. There, acting in line with the relevant objective probabilities is all that can be achieved.
Note that Sterelny (2003a, footnote 3, p. 35) seems to recognise this issue as being potentially problematic for the standard account. However, he does not consider it further.
A structurally related point has been made by Block (1981) in a different context. I thank Kim Sterelny for useful remarks about this matter.
Of course, given the complex connections between inputs and internal states on the one hand, and beliefs and desires on the other, an organism with beliefs and desires could also (if it so ‘chose’) make the cognitive problem more complex. However, this is not so relevant here: the point is just that it can make it easier.
For expositional convenience, I here concentrate on beliefs and input states only. However, all the arguments carry over when desires and internal states are considered as well.
Note that I am using ‘efficiency’ in a wide sense here, as including matters of speed, reliability, and resource frugality. I thank an anonymous referee for pointing out the need to be clearer about this.
This also fits with many other investigations that have found that, often, the simpler approach to a problem can be the more successful one (see e.g. Dennett 1989; Forster and Sober 1994; Gigerenzer and Selten 2001; Sober 1998b, 2001, 2008, 2009). However, unlike what is true in these other contexts, the issue here is not a methodological or epistemological point, but anengineering one.
This does not mean that this must be the only reason why natural selection has favoured beliefs and desires over reflexes. The point is just that cognitive efficiency—unlike flexible responding—is one (key) reason for why it might have done so; other such reasons may exist.
Note that this statement should not be read as implying that belief/desire-driven organisms get rid of their reflexes altogether (see notes 7 and 9). In fact, it is quite likely that an organism will want to retain some of its reflexes even after it switched to using beliefs and desires. This is due to the fact an organism’s table of reflexes need not have a uniform potential to be simplified: in particular, some of an organism’s actions might only be connected to very few prompts, so that there will not be major efficiency gains from making these actions belief/desire-driven.
Alternatively, it could be said that whereas the standard account focuses on the fact that one input state can be associated with many different beliefs (and similarly for internal states and desires), my account focuses on the fact that many different input states can be associated with only one belief (and similarly for internal states and desires).
A non-psychological example might make this clearer (see also Sober 2008, Chap. 3). Assume that the mammalian camera eye is the best available eye design. Should we therefore expect that all organisms have these kinds of eye? Not necessarily—since evolution is based on ‘gradient climbing’ (i.e. the incremental improvement of a trait from a given starting point), whether an organism evolves a camera eye depends on what kind of eye design it started out with. Now, in some circumstances, it may be the case that switching from a non-camera design to a camera design requires changes that, intermittently, lead to worse eyesight. In these circumstances, the relevant organism might not evolve a camera eye – and that is so even if the latter eye design is more adaptive than the one it currently has, and even if there are no constraints on the workings of natural selection.
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Acknowledgments
I would like to thank Elliott Sober, Dan Hausman, Larry Shapiro, Kim Sterelny and an anonymous referee of this journal for many useful remarks about previous versions of this paper.
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Schulz, A.W. The adaptive importance of cognitive efficiency: an alternative theory of why we have beliefs and desires. Biol Philos 26, 31–50 (2011). https://doi.org/10.1007/s10539-010-9229-z
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DOI: https://doi.org/10.1007/s10539-010-9229-z