Several workers have demonstrated a relationship between anxiety and critical flicker frequency (CFF); among these are Krugman (1947), Goldstone (1955) and Friedl (1954). Unfortunately the trait ofanxietyis not unidimensional, being a compound of neuroticism and introversion, so that these data might indicate a lower threshold of CFF for neurotics, or for introverts, or for both. The second of these interpretations has been tentatively adopted (Eysenck, 1957), in spite of some questionnaire evidence to the effect that thresholds are lower for extraverts (Washburnet al., 1930; Madlung, 1935; Simonson and Brozek, 1952). The main reason for not considering this additional evidence too convincing lies in the curious nature of the measures used to determine extraversion-introversion; these seem to compound introversion and neuroticism, as pointed out elsewhere (Eysenck, 1960). However, when we take into account the rather strong evidence regarding drug effects (Simonson and Brozek, 1952; Landis, 1954), which tends to show that stimulant drugs raise the threshold, while depressant drugs lower it, as well as the fact that brain injury tends to lower the threshold (Enzeret al., 1944; Halstead, 1947; Landis, 1949; Werner and Thuma, 1942), then the case against this tentative hypothesis becomes rather strong. It may be that the attempt to relate CFF to only one dimension of personality was mistaken, and that CFF is related to both neuroticism and extraversion, in the sense that low thresholds characterize the more neurotic and the more extraverted person. This hypothesis would certainly account for all the available facts better than the original hypothesis.
B-31Single Word Reading as a Test of Premorbid Functioning in Chronic Severe Acquired Brain Injury