When operating a vehicle, the driver's eye may focus on either the windshield or the distant object. Circumstances have been documented where the interposed surface provides a stimulus to visual accommodation which produces loss of acuity for details of the distant object. The apparent size of an object has been shown to relate to accommodation distance. Two experiments are described which investigated the relationship between the trapping of accommodation at a near distance (Mandelbaum effect) and changes in the apparent size of an object. In the first study, 24 observers reported smaller size with nearer accommodation and larger apparent size with farther accommodation at a better than chance rate. The 12 observers in the second study showed a consistent diminution of mean apparent size of an object as a screen was moved nearer to them. The implications for vehicle control in automobile and aircraft operation are examined. For the covering abstract of the conference see IRRD 268805.
Samenvatting