Planning routes around the world: International evidence for southern route preferences

Abstract

Three studies test whether the southern route preference, which describes the tendency for route planners to disproportionately select south- rather than north-going routes, can be attributed to regional elevation patterns; specifically, we ask whether this effect replicates in three topographically disparate international regions, one of which is characterized by higher elevations to the north and lower to the south (Padua, Italy), and two characterized by higher elevations to the south and lower to the north (Enschede, Netherlands; Sofia, Bulgaria). In all cases, we found strong evidence that route planners disproportionately select south- rather than north-going routes at rates exceeding chance. We conclude that the southern route preference is driven by strong associations between canonical direction and perceived effort of route traversal; these effects are somewhat perplexing given that such associations are not founded in the reality of physical space.

Introduction

Navigating through complex environments involves not only the application of spatial knowledge about routes and environmental structure, but also heuristics or rules of thumb that help individuals develop and follow route plans. Thus, while navigators consider several basic spatial and temporal characteristics when selecting routes, such as path length and complexity, and traffic patterns (Bovy & Stern, 1990; Gärling, Lindberg, & Mantyla, 1983; Golledge, 1995; Seneviante & Morrall, 1986), they also show some relatively counterintuitive behaviors. For instance, navigators tend to select long and straight initial route segments when leaving an origin, and select the last available turn when approaching a destination (Bailenson, Shum, & Uttal, 1998, 2000; Christenfeld, 1995). Interestingly, these heuristics are sometimes applied at the expense of neglecting shorter route options. We recently discovered that navigators also show a consistent bias toward selecting generally south-going rather than north-going routes between an origin and destination, even when these routes are equated for path length and complexity (Brunyé, Mahoney, Gardony, & Taylor, 2010). A series of six experiments suggested that participants might misperceive the northward canonical direction as ‘uphill’ relative to the southward direction (see also, Nelson & Simmons, 2009).

The precise source of this southern route preference remains elusive – why might participants perceive the northward canonical direction as ‘up’? One possibility is that participants from the New England region of the United States transfer their knowledge of local large-scale elevation patterns to laboratory tasks involving a degree of uncertainty. That is, participants may strongly associate canonical and vertical space because the New England region is characterized by higher elevations (mountains) to the north and lower elevations (sea level) to the south. In turn, this learned association drives the southern route preference in an effort to avoid the physical cost of locomotion through mountainous regions. The second possibility is that participants associate canonical and vertical space in a manner nonspecific to their local environments. Indeed some recent work suggests that participants may implicitly associate north with higher elevation (Brunyé et al., in press; Gagnon, Brunyé, Robin, Mahoney, & Taylor, 2011) at a level outside of conscious awareness. This association may be driven by a somewhat pervasive links between vertical upward space and increased effort that carries over onto representations of canonical direction.

To test whether associations between canonical and vertical space extend across cultural and geographical populations, we conducted a series of studies specifically aimed at recruiting participants from international regions characterized by dramatically varied relationships between canonical and vertical/topographic space. Below we review the extant literature examining route-planning asymmetries and further detail the southern route preference as a means of elucidating this project's motivations and our hypotheses' supporting research.

In many cases, navigators choose routes based on efficiency and familiarity, reviewing the relationship between an origin and destination and selecting a viable path between them (Benshoof, 1970; Golledge, 1995; Jacoby, 1917). In fact, many people believe they can perform this type of route-planning task with little effort, particularly when negotiating familiar environments or using a standard road atlas (Gärling & Gärling, 1988; Ueberschaer, 1971). However, when there are multiple route options and increased uncertainty regarding an objectively ‘correct’ decision, navigators apply a wide range of spatial heuristics. For instance, participants tend to select routes that have fewer turns and pass fewer landmarks along the way (Sadalla & Staplin, 1980; Seneviante & Morrall, 1986). Further, research regarding the least-angle strategy demonstrates that when people are presented with multiple route options from an origin to a destination, they tend to select the route that deviates minimally from the destination's overall direction (Conroy Dalton, 2003; Hochmair & Frank, 2002; Hochmair & Karlsson, 2005). Participants also show an initial segment strategy, which describes the reliable tendency to select routes that have a relatively long and straight path segment emanating from an origin (Bailenson et al., 1998, 2000). Finally, we recently discovered that people show a southern route preference during route planning that leads to a disproportionate (approximately 63% of the time) selection of south- relative to north-going routes between waypoints (Brunyé et al., 2010). For further descriptions of heuristics and their application to route planning, see (e.g., Hölscher, Meilinger, Vrachliotis, Brösamle, & Knauff, 2006; Janzen, Herrmann, Katz, & Schweizer, 2000; Wiener, Lafon, & Berthoz, 2008).

In many cases, heuristics, like those described above, can decrease cognitive workload (i.e., Christenfeld, 1995), and lead to effective path selection. Indeed a number of studies suggest that navigators will use heuristics to simplify route plans in an attempt to reduce the cognitive and physical costs associated with maintaining and carrying out a route sequence (Freska, 1999; Levine, 1982). In some cases, however, these heuristics can lead to suboptimal route selection. For instance, participants will place disproportionate reliance upon the initial route's straightness even when it leads to selecting an overall lengthier path (Bailenson et al., 2000). There is thus some compelling evidence that predicting wayfinding behavior involves not only identifying the shortest or most efficient route, but also identifying and characterizing the heuristics that guide spatial decision making. Interestingly, many of these heuristics appear to be implicit, operating outside of a navigator's awareness (Bailenson et al., 1998; 2000; Brunyé et al., in press; Christenfeld, 1995). The wide range of heuristics and their strong influence on navigation behavior illustrate the importance of continued research in elucidating the full range of spatial heuristics guiding navigation. Results from this research carry important implications for the theoretical and computational modeling of human spatial behavior (Golledge, 1995; Kuipers, 2000; Yoshino, 1991), and predicting wayfinding behavior in applied contexts (i.e., in the lost, Heth & Cornell, 1998; or for environmental engineering, Gärling & Gärling, 1988; Raubal, 2002; Weisman, 1981).

We recently reported six experiments examining navigators' route selections under conditions of uncertainty (Brunyé et al., 2010). In our first two experiments, participants viewed maps of unfamiliar large-scale environments and planned routes between landmark pairs. The maps were presented on a standard computer monitor in front of the participants. On each map, half of the landmark pairs were diagonally across the map from one another (filler trials), and half involved a dilemma between north-south or east-west route options. On dilemma trials, participants were tasked to plan a route between two map landmarks that were horizontally (north/south) or vertically aligned (east/west), and had two equal-length route options for navigating between them. Dilemma routes were designed to promote route selection under conditions of relative uncertainty – that is, no objectively ‘correct’ route option was available. Across participants, we controlled for number of turns and landmarks, and right-on-red affordances (i.e., the ability to turn right at a red traffic signal) offered by each dilemma route option. We found that, on average, participants demonstrated a southern route preference on approximately 63% of north/south dilemma trials, but no reliable bias with east/west dilemma trials. Experiments 3 and 4 demonstrated that this southern route preference could not be attributed to misperceptions of route length, or a spatial viewing preference on the computer monitor. Experiments 5 and 6 demonstrated that participants rate north-going routes as having a higher potential for scenic vistas, require more calories to traverse, and are associated with longer travel times relative to south-going routes.

According to these results, participants seem to misperceive northern routes as moving uphill toward higher elevations. The source of this effect, however, is unknown. The fact that the northward direction is most frequently oriented upward on maps, atlases and even GPS devices may lead people to associate north with the upward direction. Of course, the upward direction relative to the vertical body axis is inherently more difficult than the downward direction (Staab, Agnew, & Siconolfi, 1992). It could be the case that participants transfer their knowledge of how gravity affects movement effort to decisions regarding unfamiliar environments. Such a possibility was raised by Shepard and Hurwitz (1984) in their examination of links between various three-dimensional spatial axes. If so, participants may use effortful attempts to reduce predicted workload and thus strategically avoid traveling through what they (mis)perceive as physically demanding areas. Some recent evidence from our laboratory provides support for this hypothesis: when using an adapted implicit association task (IAT; Greenwald, McGhee, & Schwartz, 1998) we find strong implicit directional associations between north/south cardinal directions and vertical spatial axes (Brunyé et al., in press).

However, much of the evidence for the southern route preference is gathered from students at a New England university. The large-scale topographical patterns characterizing New England show dramatically higher elevations to the north (i.e., the White and Green Mountains in NH and VT, respectively) than to the south. Participants may thus transfer their knowledge of regional topography to decisions regarding unfamiliar space. In our earlier work, we proposed that it remains to be discovered whether the southern route preference will replicate in areas with different or even opposite elevation patterns (e.g., mountains to the south, lower elevations to the north). The current work accomplishes this goal by replicating our earlier route-planning experiment in three international regions suitably characterized by different elevation patterns (see Fig. 1): Padua, Italy (1a), Enschede, Netherlands (1b), and Sofia, Bulgaria (1c). Similar to New England, Padua is characterized by mountains (the Italian Alps) to the north, and relatively low and level terrain to the immediate south. Enschede is characterized by level areas to the immediate north and south, but higher elevations to the distal south and sea level elevations to the distal north. Sofia is characterized by topography that is decidedly opposite to that of the New England area, with level areas to the immediate north and a dramatic mountain range to the immediate south.

If the southern route preference is due to transferring knowledge of regional elevation patterns to route-planning decisions regarding unfamiliar environments, then such an effect should be replicated in the Padua, Italy sample, diminished in the Netherlands sample, and perhaps reversed in the Bulgaria sample. In contrast, if the southern route preference is due to strong associations between coordinate axes and vertical space, then such an effect should replicate in all regions. Specifically, if people more generally associate north with the upward direction and south with the downward direction, then the southern route preference should replicate in all international samples, regardless of local topography.