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{"created":"2022-01-31T12:57:56.695852+00:00","id":"lit28775","links":{},"metadata":{"alternative":"Studies from the Yale Psychological Laboratory","contributors":[{"name":"Scripture, Edward W.","role":"author"}],"detailsRefDisplay":"Studies from the Yale Psychological Laboratory 2: 120-121","fulltext":[{"file":"p0120.txt","language":"en","ocr_en":"A PSYCHOLOGICAL METHOD OF DETERMINING THE\nBLIND-SPOT,\nBT\nE. W. Scripture.\nNo greater misfortune could happen to psychology than to have it supposed that its measurements were physical or physiological rather than purely mental. The phenomena of consciousness are not unattainable things situated at the central termination of nerve-paths; they are directly given, purely mental facts known to every savage or child regardless of the existence of brain or nerves or sense-organs. As purely mental facts we can measure them by one another with an accuracy rapidly approaching that of physics. As mysterious processes resulting from a complicated succession of physiological changes, we can do nothing with them.\nThe treatment of the blind-spot is a striking illustration of the difference in the physiological and the psychological points of view.\nIn Helmholtz\u2019s Physiologische Optik the blind-spot is treated as a physiological matter and is used to prove that the optic nerve is not directly sensitive to light. The first step, however, is mental; in our field of vision we find a constant spot on which we are blind. We may know nothing about the optic nerve or the function of the eye, but the fact of blindness can easily be made apparent. It is my object to show how this blind-spot can be measured as a fact of consciousness without the assumptions of the passage of rays into the eye, etc. After such psychological measurements have been made, the results can be compared with the position of the Papilla nervi optici in relation to the optical axis of the eye and its non-sensitiveness can be deduced.\nThe apparatus required consists of a board with a straight side (drawing-board), a T-square, a draughtsman\u2019s triangle or a straight piece of wood or metal to be used as a sliding piece against the square, a millimeter-scale and three pins. Two pins are pounded into the board close to the straight edge; the head is fixed so that one is seen exactly behind the other. The other pin is fastened into the sliding piece or triangle and is moved from one side in a line at","page":120},{"file":"p0121.txt","language":"en","ocr_en":"Method of determining the blind-spot.\t121\nright angles to the line of the two pins until it just disappears; this is the edge of the blind-spot. The T-square is now moved nearer or farther away and the measurement repeated. The results for the left eye are indicated in the diagram.\nThe two vision-pins are at any points a and b. The edge of the T-square is put at c; at the point e the movable pin disappears. When the T-square is placed at d, the pin disappears at f What is the angular distance of the edge of the blind spot from line of regard? Drag/y parallel to ah] this gives gfe\u2014cp as the angle to be determined. Since ge \u2014 ce \u2014 df, and gf= cd, we get at once\ntan cp =\nce \u2014 df cd\nIf we thus determine cp for the inner edge and in a like manner cp' for the outer edge of the blind-spot, the angular diameter of the blind-spot is qj\u201c=cp' - <p.","page":121}],"identifier":"lit28775","issued":"1894","language":"en","pages":"120-121","startpages":"120","title":"A psychological method of determining the blind-spot","type":"Journal Article","volume":"2"},"revision":0,"updated":"2022-01-31T12:57:56.695857+00:00"}