Analysis of eye movements during free search.

The positive polarity of the human cornea was used to produce signals from marginal electrodes around the eyes. The potentials were amplified with dc networks which produced amplitude-time oscillographic tracings of the horizontal and vertical components of eyeball movement, and also controlled the deflectors of a cathode-ray oscilloscope (CRO) in such a way that the beam moved in the same way as the eyes. An automatic camera photographed the CRO face to produce two-dimensional electro-oculographic (EOG) plots of eyeball movement. Data thus obtained are used for an analysis of eye movements and fixations in a surveillance search task. The paper oscillographic tracings against time show (1) the number of fixations per unit of time, and (2) the duration of the fixations. The cathode-ray EOG shows (1) the order of fixations in search procedure, (2) the lengths of various saccadic jumps, and (3) the areas of neglect and concentration for 5-sec search periods on a circular field subtending 30° of visual angle.