XV.
COMMUNICATIONS
A.
N.
R.
G.
Prof. W. A. Rosenblith
Prof. R. C. Booton, Jr.
Dr. J. S. Barlow*
Dr. M. A. B. Brazier*
Dr. D. H. Raab
A.
E.
E.
M.
S.
BIOPHYSICS
Albert
Berg
Brown
Fahringer
BEHAVIORAL REACTION TIMES TO ACOUSTIC
S. Frishkopf
H. Goldstein, Jr.
Y. S. Kiang
Petron
Pulsifer
CLICKS
Subjects placed in a dimly-lit anechoic chamber were instructed to press a microswitch as soon as they heard a click presented to them by an earphone. The click was
always preceded by a warning light of fixed duration.
The warning light and the click
were separated by a variable time interval so that the subjects were not able to anticipate the click. The data presented below were selected for a time interval of 2. 5 sec
between the onset of the warning light and the click; this time interval yielded on the
average the shortest reaction times. The simple reaction times were measured by
The subjects were trained separately on clicks approxi-
means of an electronic counter.
mately 60 db above their respective thresholds until their performance had stabilized.
Then simple reaction times were determined for five different intensities of the click.
260
250
SUBJECT
240
SUBJECT B
SUBJECT C
A
230
u' 220
o 210
_ 200
Z 190
0,_
I
180
+
0
o
w
Ir
-0,~
II
it't'
-70
-60
I
-50
I
-40
I
I
-30
-20
i
-10
I
I
0
CLICK INTENSITY (DB BELOW REFERENCE LEVEL)
Fig. XV-1
Mean reaction time vs. click intensity.
From the Neurophysiological Laboratory of the Neurology Service of the Massachusetts General Hospital.
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(XV.
COMMUNICATIONS BIOPHYSICS)
a
O
0
SUBJECT
SUBJECT
SUBJECT
A
B
C
".
-0
0-r-0
II
-80
,
-70
,
-60
I
i
-50
-40
CLICK INTENSITY
-30
-20
I
i
-10
0
(DB BELOW REFERENCE LEVEL)
Fig. XV-2
Percentage of deviation (standard deviation/mean) vs. click intensity.
Figure XV-1 presents the mean reaction times for three subjects; each point represents
at least 100 judgments, but in most instances 200 judgments.
(It may, in this connec-
tion, be worth while to recall that the onset latency of evoked electrical responses to
clicks at the auditory cortex of anesthetized animals is roughly 1/100 sec.)
Figure XV-2 plots the standard deviation as a percentage of the mean (coefficient
of variation).
The data mentioned above were all collected in so-called "fixed-intensity-
runs," that is,
in each experimental session clicks were presented at a single intensity
level only.
is,
For one of the subjects we have also data for "mixed-intensity-runs," that
for sessions in which the five intensity levels were presented randomly.
to the fixed-intensity-run data, there is
Compared
a tendency toward an increase of the mean
reaction time, and there is a consistent increase in the coefficient of variation.
N. E. Berg, A. E. Albert
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