From Brains to Branch Points:
Cognitive Constraints in Navigational Design

A Dissertation

Definitions  Design Elements Design Principles

Design Elements and Principles for
Environmental Locomotional Design in Support of Wayfinding

2004-06-28

Definitions

A locomotional structure is a set of interconnected locations and paths. It comprises the following elements:

Location A place where something is or could be located; a site.
Path A connection that allows locomotion between two locations.
Branch region A set of contiguous locations at which the same locomotional options are available and a decision can be executed.
Locomotional option A path that connects two adjacent branch regions directly (i.e., with no intervening branch regions); a.k.a. a path segment.

Two locomotional options are considered equivalent if they

bulletConnect the same two branch regions, and (optionally)
bulletfollow the same trajectory through space
bulletand/or pass through the same set of information access regions
Information access region A set of contiguous locations at or from which particular information may be perceived.

Design Elements

1. Environmental Locomotional Structure

An environmental locomotional structure is a locomotional structure that is actually offered by an environment.

The environmental locomotional structure(s) available to a navigator defines the navigational problems that must be solved and dictates their complexity.

2. Relationship Between Environmental Locomotional Structure and Task-Defined Structure

A task-defined [locomotional] structure is the locomotional structure that is necessary to completion of a particular task. A task-defined structure comprises destinations and routes:

Destination A location that must be reached in order to accomplish the task in whose service navigation is undertaken.
Route A path that leads to a destination or that must be followed in order to accomplish the goals of the task in service of which navigation is undertaken.

In other words, a "task-defined structure," "destinations" and "routes" are defined functionally, by a particular task rather than by the environment.

The relationship between the environmental locomotional structure and the task-defined structure determines how much cognitive overhead is introduced by the navigation task.

3. Relationship Between Environmental Locomotional Structure, Informational Design and Perceptual Design

Informational design determines what information is present in the environment.

Perceptual design is the design of sensory stimuli and their behavior.

The relationship between the environmental locomotional structure, informational design and perceptual design determines what environmental information may be available to the navigator and when it is available.

4. Relationship Between Environmental Locomotional Structure and Movement

Steering is the cognitive and physical task of controlling movement.

The relationship between the environmental locomotional structure and movement determines how much time the navigator has to acquire information and to make and execute navigational decisions. It also determines how much cognitive overhead is introduced by steering.

Principles for Design of an Environmental Locomotional Structure

# Name Principle

1

 Locations and Paths The locations and paths offered by the locomotional structure must be a superset of the destinations and routes in the task-defined structure.
2 Number of Branch Regions Increasing the number of branch regions in the locomotional structure is likely to increase wayfinding difficulty, and decreasing the number is likely to decrease difficulty.
3 Complexity of Branch Regions The fewer options offered in a branch region, the simpler the wayfinding will be.

4

 Task Logic and Organizing Principle The more closely the logic of the organizing principle of the locomotional structure corresponds to the logic of the task, the less overhead is introduced by wayfinding cognition.
5 Simplicity of Organizing Principle Within the organizing principles made possible by the task, the simpler the principle, the simpler the wayfinding
6 Discontinuities in Plan Organization Discontinuities in the plan organization increase the likelihood of wayfinding error.
7 Route Complexity The more branch regions along a route, the greater the likelihood of wayfinding error along it.
8 Location of Information Access Regions Information access regions must be located within the locomotional structure if they are to figure in wayfinding.
9 Precedence of Information Access Regions An information access region entry port must precede or coincide with its associated branch region exit ports, if the information the information region provides is to figure in any wayfinding decisions executed at that branch region.
10 Branch Region Speed The less time—per non-viable option—allowed in a branch region, the higher the likelihood of wayfinding error.
11 Information Access Region Speed The less time—relative to the amount of information offered—allowed in an information access region, the less likely the information offered is to figure in wayfinding.
12 Steering and Locomotional Structure The fewer or less precise steering actions that are required to follow the selected route and to remain within the locomotional structure, the fewer wayfinding errors are likely.
13 Automated Branch Regions An automated branch region decreases the difficulty of wayfinding if it is well-automated, but increases the difficulty if it is poorly-automated.
14 Alternative Routes Alternative routes to destinations may decrease wayfinding performance, but increase the likelihood of wayfinding success, particularly if they are clustered around the optimal route.
15 Hidden Branch Regions Hidden branch regions decrease the cognitive overhead wayfinding substantially if they are well-automated, but increase it substantially if they are not.

Hypothesized principles are shown in italic.