in partial fulfil]ment of the - MSpace - University of Manitoba

81
A non-reflective black turntable of 15 cm diameter, with 3 red and 1
blue discs (poker chips) mounted at equidistant positions, was used to
test the fluctuation in the perception of the purkinje-shift during dark
adaptation. À circular gray spot was placed at the center of the turntable
and the sides of the turntable had different luminous symbols,
visible only to the investigator, to indicate the position of the odd
disc (i.e., the bLue disc). Experiment II r+as carried out '10 minutes
after completing experiment I (Thornton' s and 1 0-Second Tests ) . Each
subject was light adapted for one minute by fixating on a white, 65x50
cm paper placed on the work surface. The set up of the light source for
light-adaptation for experiment II was the same as that for experiment
I.
Each subjecL was light adapted, just before the actual testing began,
for one minute by fixating on a whiLe hard paper (65 x 50 cm) placed on
the work surface. Immediately after one minute of light adaptation, the
lighting was dimmed to 0.02 u l.latt (scotopic range). Recording of time
using a stopwatch started when the subject was able to identify the gray
spot on the center of the turntable. Àc this time the turnlable was
spun every 4.88 seconds, and the subject was forced to make a decision,
i.e., to point out the blue disc. The 4.88 second mark was determined
by a tape recorded sound which was heard every 4.88 seconds. All correct
and incorrect decisions were recorded until 7 correct consecutive
decisions were achieved. The time of the last correct decision was used
to determine Lhe tesl time. If the subject couldn't identify the disc
or rlas not sure of the location of the test disc, he/she was allowed to
9UeSS.