Cognitive Aspects: How People Perceive, Memorize, Think and Talk About Landmarks - Landmarks: GIScience for Intelligent Services - page 89

that both types of landmark references serve different purposes—the first one is
anchoring an action of orientation decision making, while the second one is not
linked to any decision and thus rather of calming or confirming nature—the different
observations between the studies can relate to different contexts. Environments with
longer route segments suggest intermediate confirmatory comments, especially for
instruction followers unfamiliar with the environment.
This thought matches another observation of Lovelace et al. They asked people
familiar and people unfamiliar with the environment to rate the collected route
descriptions. Again in contrast to Denis' et al. findings of high ratings and high
navigational performance with shorter route descriptions, Lovelace et al. report
a preference for richer route descriptions (inter-rater correlations showed that
subjective ratings were reliable and consistent across individuals). This preference
for richer descriptions indicates again that within their context intermediate confir-
matory references to landmarks were advisable.
Allen [ 4 ] wrote about the findings of Denis et al. on the essence of good route
descriptions: “The next step in this strategy may involve a formal description of
the structure and components of these skeletal descriptions, which consist of a
combination of directives and descriptives as described previously” (p. 335). This
is, of course, what the rest of this topic is about. But before we move on let us
have a look at Allen's own work. He demonstrated that route descriptions are better
remembered and lead to higher navigational performance when the production of
the route descriptions build in few psycho-linguistic principles:

￿ The principle of spatio-temporal order: The spatial and temporal order of

localizations in route descriptions should be consistent with the order in which
these locations are experienced when traveling along the described route.

￿ The principle of referential determinacy: References to landmarks at points

where decisions about orientation have to be made, and links to the proper action
with the experience of the landmark.

￿ The principle of mutual knowledge: Delimiters describing topological, direc-

tional and distance relations in route descriptions are chosen according to
the communication context, i.e., appropriate for the environment and for the
instruction follower.

However, all research cited so far studied route descriptions in a homogeneous
context, which typically assumes a person unfamiliar with the environment, and
in a mono-modal movement, either walking or driving a car. They emphasize the
role of decision points (for orientation) along otherwise linear route elements. One
could expect then Allen's principles be satisfied by route descriptions of single
granularity, which means one instruction per decision point. However, even in
these circumstances human route descriptions are not necessarily of a constant
granularity. Instead, elements are often grouped together (a process in memory and
language sometimes called chunking [ 35 , 103 ] ). For example, an instruction “at the
third intersection turn right” applies numerical chunking, and “follow the signs to