It has been known for some time that working in a complex environment can sharpen certain mental abilities. One of the most well-known examples is that of London taxi drivers, who have to memorize the layout of a vast city and consequently show an enlarged hippocampus, an area of the brain involved in navigation and spatial memory. A more recent study has attempted to ascertain which factors are generally important in the development of navigational skills. Subjects were asked to complete a task embedded in a computer game which involved memorising a map and then steering a boat using this mental picture. A number of factors were significant, but one of the most interesting outcomes was that there were differences between those who lived in a rural environment and their town dwelling counterparts. Country dwellers showed significantly better navigational skills, presumably because town dwellers just come to rely on street names and numbers and so these skills are less activated. Moreover, it appears that the type of city can also make a difference. Subjects from cities with a more organic, less predictable topography performed better than those from the kind of grid-based cities that are common in North America, such as Chicago. There may be a useful maxim for urban planners here, that there can be such a thing as too much simplicity when it comes to city design.