3 METHODS OF MEASURING LOCATION OF EGOCENTER - THEIR RELIABILITY, COMPARATIVE LOCATIONS AND INTERCORRELATIONS

There were discrepancies between the various assumptions and reports made regarding the location of the egocenter [the visual direction center]. Three different methods of measuring the location of the egocenter were studied. The locations of egocenters for 15 naive human subjects were determined 8 times by each method during each of 2 different experimental sessions separated by 1 wk. All 3 methods had high internal consistency as indicated by high .alpha.-coefficients. Two methods were found to have high stability over time as indicated by test-retest correlations. Using Howard and Templeton''s and Funaishi''s methods, the mean egocenter was located near the corneal plane and near the median plane, but using Roelofs'' method the mean egocenter was located 17 cm behind the corneal plane near the median plane. The intermethod correlations were uniformly low. The lack of inter-method correlation and the different mean locations among the methods suggest that, unless predictive validity is established for the 3 tasks, there is no basis for choosing among the 3 methods.