Title

Orienting to place and orienting to distance are distinct functions of human locomotion

Date of Completion

January 2007

Keywords

Psychology, Experimental

Degree

Ph.D.

Abstract

In its general form the problem of orientation is how an organism acquires and expresses knowledge of its surroundings. The present thesis addresses this problem in the context of the basic task faced by terrestrial mobile organisms: traveling from one place in their habitat to another. Two distinct orienting functions will be motivated and developed for human locomotion, namely, orienting to distance and orienting to location. Orienting to location is awareness about one's relation to the numerous places in one's environment—more precisely awareness of how one is located. Orienting to distance is awareness of the separations of places in the environment and their implications for traveling. ^ Experiment 1 consisted of a production phase in which the distance traveled from the starting location to the end location exceeded the distance between the start and end. The production phase was followed by a report phase in which blindfolded participants either walked the distance traveled between the two places (orienting to distance) or walked to the starting location (orienting to location). The results of Experiment 1 suggest that blind-walked reports of location and travel distance are distinct and reflect the basic characteristics of the distance traveled through the environment and of locations within it. Of particular significance, weighting the body during the production phase affected the blind-walked report of distance traveled but not the blind-walked report of starting location. It was concluded that the length of a path between two places is not perceived as a physical distance along a path but rather as an embodied act of traveling a route. Analyses of the kinematics of production and report suggested that traversing a given path by legged locomotion generates an unfolding pattern of mechanoreceptor stimulation specific to the length of the path. ^ In Experiment 2 the concept of orienting to location was developed through two simple tasks of blind folded walking: (a) returning to a home location H following an extended walk, and (b) finding H from an arbitrary place. These homing tasks were conducted within two different environments knowable only by haptic perception, specifically, by the activities of walking and probing with a cane. The two environments differed in richness of structure. Half of the participants became oriented to the less structured environment, and half became oriented to the more structured environment. ^ Two models for what it means to be located were considered and contrasted. In the commonplace model, place is defined in a framework of Euclidian distances and locations. In the less commonplace model, distances and locations are defined by inclusion within a layout of surfaces. In the Euclidian framework a given place is located in a coordinate system. Its location is independent of the presence of other places. In the inclusion framework, a given place is located precisely by how it is surrounded by the other places in the environment. ^ The results of Experiment 2 revealed that the ability to orient to H in the two homing tasks were dependent upon the inclusion relations. When H was more richly surrounded the precision of homing improved. Perturbations of the layout of surfaces surrounding H directly affected the perceived location of H. Even subtle changes of distal parts of the surface layout appeared to have an effect. It was concluded that the location of H was not perceived as a location in an abstract imposed coordinate system, but instead it was located by way of a nested set of potential inclusion relations defining the surface layout. ^ Experiments 1 and 2, in design and results, give weight to the intuition that goal directed action is by definition embodied and embedded. For the simple behavior considered in this thesis, that of blind walking from one place to another, the places traveled between seemed to be located by their environment (and not by a system of coordinates) and the separation of those places seemed to be perceived in respect to afforded travel. ^ The general discussion focused on the methodologies adopted in the thesis. Specifically it focused on their potential for providing further insights into the general problem of orientation and the associated problem of place learning. ^