The VFA is measured by asking an individual to fixate on a figure (inspection-figure) for a period of time, it is
removed and replaced by another figure (test-figure). The person is then asked to make a number of
judgements of this figure over a period of time (called test-time). Phenomenally, the test-figure appears
displaced, and the magnitude of this displacemnt or distortion may be measured as a function of test-time.
Schizophrenic patients between the ages of 22 and 55 years who had not received any medication for at least
48 hours, were tested within two days of admission to a psychiatric hospital. Ten patients were tested: five with
HHPO and five without HHPO. The former group consisted of four males and one female with a median age of
34 years; the latter group included three males and two females with a median age of 35 years
Apparatus and Procedure
The apparatus and procedure used to measure the VFA were the same as in earlier studies (Kelm, 1968, 1981;
Kelm and Hall, 1967), which involved the measurement of the magnitude of three pehnomenal displacements:
immediately, 30 and 60 seconds (called test-time), following 30 seconds visual fixation of the inspection-
The chemical analyses followed the same procedure as used by Hoffer and Mahon (1961). Both the VFA and
chemical tests were carried out on the same day by two technicians, neither of whom knew the purpose of the
study, nor did they collaborate with each other.
The magnitudes of the VFAs for the HHPO and HHPO-free patients at the immediate, 30 and 60 seconds test-
times are shown in Figure 1 (p. 44). A negative VFA indicates that the phenomenal inspection and test-
distance was less than in the control condition (control judgements have no prior fixation of the inspection-
figure); a positive value, greater than the control. A summary of an analysis of variance is given in Table 1 (p.
44). This analysis shows that these two groups of patients have significantly different magnitudes of figural
distortion (F = 12.250, 1 and 8 df,p<.01). It also shows that the VFA changes as a function of test-time, which
is the usual expected phenomenon (F = 27.233, 2 and 16 df, p<.001). The statistically significant interaction (F
= 6.927, 2 and 16 df, p<.01), indicates that the two groups differ in their magnitudes of distortion as a function
The first prediction that schizophrenic patients with HHPO would have different VFA magnitudes than
schizophrenics without HHPO was confirmed. The second prediction that HHPO patients would manifest
greater figural instability than the HHPO-free group was not confirmed. Instead, it was HHPO-free patients
who showed a wider range of cerebral augmenting - reducing, and thus greater perceptual instability than
schizophrenics with HHPO.
How may these data be explained? One approach which may be helpful would be to compare the HHPO and
HHPO-free VFAs with those of normal individuals. The VFA curve of five normal subjects is shown in Figure 1.
Analyses of variance show that both HHPO and HHPO-free patients have significantly different magnitudes of
figural distortion than normals (p<.01 and <.05, respectively). These results are in agreement with earlier HOD
and VFA studies which report that schizophrenic patients generally (without regard to HHPO status), have
significantly different HOD scores and VFAs than normal subjects (Barnes, 1976; Kelm, 1962; Kelm, Hoffer
& Osmond, 1981).