Directional Olfaction?
Philosophers tend to take it for granted that our sense of smell is directional or spatial only in a very attenuated sense: We can infer where a scent is coming from (using background knowledge), or we can piece it together by moving about and noticing if the smell is getting stronger or weaker, but at any particular instant a smell is either here or not here, to some degree of intensity. Scents are not fundamentally and intrinsically experienced as coming from a particular direction. (This view goes back at least to Condillac, in his famous example of the statue endowed only with a sense of smell.)
An interesting article, by Jess Porter and others, in the current issue of Nature Neuroscience challenges this view. Subjects were blindfolded, equipped with noise-blocking earmuffs, and given knee- and elbow-pads and workgloves, then asked to track an olfactory trail that bent across a lawn (produced by a string that had been soaked in diluted odorant). They crawled on hands and knees, noses near the ground. Most could in fact follow the trail. (Woof!)
Each nostril draws smell from slightly different regions of space (a fact Porter and colleagues presented as "contrary to the common notion" but which at least used to be widely known among research psychologists -- as discussed, e.g., in Titchener's [1901-1905] Experimental Psychology). This raises the possibility of directional, "stereo" smelling -- discerning the directionality of a scent by the difference between its strength in the two nostrils.
To support this idea, Porter and her colleagues had subjects perform the task with one nostril closed or wearing a "nasal prism device" intended to mask the stereo effect by creating one "virtual nostril". As predicted, these manipulations significantly impaired performance on the scent-tracking task.
Unfortunately, it seems to me that those last results might be explainable by supposing a general decrease in olfactory sensation, rather than a specific cancelling of the stereo effect, since it's not clear that the researchers tested sufficiently whether having one nostril closed or wearing the "nasal prism" impaired olfactory ability generally.
(Thanks to Paul Hoffman, by the way, for the pointer to the Porter article.)