Book reviews

J. Roger Saydah. The Ethical Theory of Clarence Irving Lewis. Athens, Ohio: Ohio University Press, 1969. Pp. 171. Indexed. $7.50.

Nicholas Rescher. Many‐Valued Logic. New York: McGraw‐Hill Book Co., 1969. Pp. ix, 359.

EVA Schaper. Prelude to Aesthetics. New York: Humanities Press, 1968. Pp. 179. Indexed. $6.50.

N. Fotion. Moral Situations. Yellow Springs, Ohio: The Antioch Press, 1968. Pp. 124. Indexed. $4.75; paperback $1.05.

John and Shirley Lachs, eds. Physical Order and Moral Liberty. Previously Unpublished Essays by George Santavana. Nashville, Tennessee: Vanderbilt University Press. Pp. xiv, 322. $7.95.

D. C. Armstrong. A Materialist Theory of Mind. New York: Humanities Press, 1968. Pp. xi, 372. Indexed. $8.50.

Annali della Facolta di Lettere et Filosofia, Pubblicazioni dell’ Universita di Barni, Volume XII, Adriatica Editrice, Bari, 1967. Pp. 251.

Bernard Zylstra. From Pluralism to Collectivism: The Development of Harold Laski's Political Thought. New York: Humanities Press, 1968. Pp. 236. $8.00.

Andrew J. Reck. The New American Philosophers: An Exploration of Thought Since “World War II. Baton Rouge, La.: Louisiana State University Press, 1968. Pp. xxii, 362. $8.95.

Elizabeth Ramsden Eames. Bertrand Russell's Theory of Knowledge. New York: George Braziller, 1969. Pp. 240. Indexed. $6.00.     

Hemifield differences in perceived spatial frequency

Measurements of the perceived spatial frequency of stationary sinewave gratings were made with the gratings presented at the same eccentricity in the left, right, upper, and lower visual hemifields. Ten subjects performed the task binocularly with spatial frequencies of 1, 2, and 4 cycles deg-1. Two of these subjects also performed the task monocularly at 2 cycles deg-1. In the majority of cases, the spatial frequency of stimuli presented in the left and lower visual hemifields was overestimated relative to stimuli presented in the right and upper visual hemifields. The results were similar for all spatial frequencies tested, and the direction of the asymmetry was the same whether viewing was with the left eye, right eye or binocular, suggesting that the differences in perceived spatial frequency are not retinal in origin.