Nonvisual navigation by blind and sighted: Assessment of path integration ability.

Blindfolded sighted, adventitiously blind, and congenitally blind subjects performed a set of navigation tasks.The more complex tasks involved spatial inference and included retracing a multisegment route in reverse, returning directly to an origin after being led over linear segments, and pointing to targets after locomotion.As a group, subjects responded systematically to route manipulations in the complex tasks, but performance was poor.Patterns of error and response latency are informative about the internal repredentation used; in particular, they do not support the hypothesis that only a representation of the origin of locomotion is maintained.The slight performance differences between groups varying in visual experience were neither large nor consistent across tasks.Results provide little indication that spatial competence strongly depends on prior visual experience.Effective navigation by humans involves a number of skills, including updating one's position and orientation during travel, forming and making use of representations of the environment through which travel takes place, and planning routes subject to various constraints (shortest distance, minimal travel time, maximum safety, etc.); see Rieser, Guth, and Hill (1982);Strelow (1985).Methods of updating position and orientation can be classified according to the type of information used: position, velocity, or acceleration.Position-based navigation (called pilotage or piloting) relies on external signals indicating the observer's position and orientation (Baker, 1981;Etienne, 1992); such signals would include visible or audible landmarks known to the traveler or those from electronic navigation aids.Velocity-