pigs, positions, preferences: the zeugmatics of causal theories
The problem with the typical gloss is, to my mind, that it encourages a conflation which for shorthand could be described as an undiscriminating amalgamation of reasons and causes. It conflates the causal processes which lead me to perform certain actions (a bias for the right guides my choices) with the teleological ends of these actions (the reason I chose the socks because they had a pig on them) - bringing both of these under a global concept of 'reason for action' which is obfuscatory as regards the different logics of the different forms of explanantia. (The tendency I've commonly met with is to bring these two forms of explanation together by placing the teleological ends as the contents of desires and to see these desires as entering competitively into the matrix of causes which guide our actions.)
This, it seems to me, just won't do. Let us accept that desires have a dispositional form. If I like little piggy socks then, everything else being equal, I will avail myself of some. Desires, that is, are not individuated simply through our avowals ('I like piggy socks') but also through our actions (getting ourselves some piggy socks). Let us accept too that I'm sometimes or often unaware of the efficient causes of my actions (thus I just didn't know that I'm more likely to pick things on the right of a line). Finally let us accept that we may be prone to offering post-hoc rationalisations or justifications of our choices by references to appealing features of the objects chosen. It still doesn't follow, I want to claim, that it is perspicuous to present the findings of the experiments with a sentence like "You thought you chose them because of the pig symbol, but really you chose them because of their position".
My confidence regarding my desires (2) may be overinflated. My lack of knowledge regarding the determinants of my actions (1) may be deflating. Nevertheless my overconfidence in my desires (2) is not to be understood as a pretence to the same kind of self-knowledge as would be held by someone who knows better than I the determinants of their actions (1). To say "You thought you chose them because of the pig symbol, but really you chose them because of their position" is not itself logically wrong-headed, but then neither is Dickens' zeugma: "Miss Bolo went home in a flood of tears and a sedan chair". Unlike the scientific naturalist, however, Dickens remained content to play; we are not asked by him to take seriously the idea that on another occasion, whilst we thought Miss Bolo went home in a sedan chair, actually she went home in a flood of tears.