‘Tapun 1, Standard deviations in log mL. of inter-modality matches in the dark-adapted condition.
Comparison
Ss stimulus
loudness (dB) ‘Test flash duration (msec.)
rT 2 5 Or |) 200-500-1000
% 39 38 AB 32 Qt 808
BB 86 64 TM 58 38 5B As
97 BT 50 65 7 73 6568
% 60 5880 68 8 59 BB
KT 86 32 58 780
oT 530 52TH “i 70 BAR
% 38 31 OS 8G
BI 86 BB ee ee)
oT 66 18 G47 71 7 OT
6 3B 49 4890
Combined 86 53 BT LO LBC
97 6 6 Tl 73 66 69
‘Tasre 2. Standard deviations in log mL. of inter-modality matches in the light-adapted condition.
Comparison
8 stimulus
loudness (dB) ‘Test flash duration (msec.)
1 2 5 10 2 «50 1002005001000
KT 97 Bt 43 BT TRB ew wR
BI 97 ne 3 6 88 GBT
Combined 97 4600°«S1 48 er
Taste 3. Standard deviations in log mL, of intra-modality matches in the dark-adapted condition.
Comparison
flash
8 luminance
(log mL.) ‘Test flash duration (msec.)
1 2 5 10 20 «50 1002005001000
10 31 33GB a a re
BB 20 49 45 8789 Bt dl 2688
3.0 3500087 ST 30000 88 TBS
10 46°87: aL AT BT
KT 20 400 5059 38 308
3.0 430 4658 2 360
10 29 8286. al 8G
BI 2.0 Al 384088 370 46 BE
3.0 450 BL 60d A 868d
10 Bo Bh Bk HO aT
Combined 20 4 43 4k 5D 8G BB
3.0 Bo lO GB



L (log mL)

Fiecre 10,

© 1.0 fog mi
© 2.0 log me
2 3.0 log mi

3.0

25F

2.0

35

L (log mt)

© 1.0 fog me
© 2.0 log mi
33.0 log mL

10 20. 50

1 (msec)

100 200 500 1000

Mean test flash luminance required for an
modality match {o three comparison stimulus
brightnesses as a function of test stimulus duration
for Subject KT in the dark-adapted condition. Each
mean represents 58 matches.

20 50
1 (msec)
Fievre 11,

intr:

modality

100 200 500 1000

Mean test flash luminance required for an
match to three comparison stimulus

brightnesses ax a function of test stimulus duration,

Data of the three subjects
condition are combined.

in

the dark-adapted


There is even a slight tendency for the effect to
be greater with dark adaptation in their study.
Baumgardt’s method was different in that he
used hapaloscopic presentation of stimuli in a
brightness matching task. The possibility re-
mains that dark adaptation may have an in-

.—lllCO Oo

hibiting effect as observed in the current study
and by Baumgardt when comparison stimuli and
test stimuli are not presented to the same eye in
a brightness matching task, or if a method of
measuring brightness is used which does not
involve a visual comparison stimulus.

3.57
35
© 75.48
© 86 a8
0 97 4B
3.0
25
3
E a
E
z
= 20 3
4 = 20
4
Lop 1s
tof 10
12 5 10 20 50 100 200 500 1000 2 5 10 20 50 100 200 500 1000
+ (msec) t (msec)
Figure 1, Mean test flash luminance required for inter- Fieure Mean test flash luminance required for inter-
modality matches to three comparison stimulus modality matches to three comparison stimulus

loudnesses as a function of test stimulus duration
for Subject BB in the dark-adapted condition, Each
mean represents 44 matches.

loudnesses as a function of test stimulus duration
for Subject BJ in the dark-adapted condition. Each
mean represents 48 matches.



Tarte 4, Standard deviations in log mL. of intra-modality matches in the light-adapted condition.
Comparison
flash
8 luminance
(og mL.) Test flash duration (msec.)
rT 2 5 1 2 ©=50 1002005001000
10 45 3388 43 8888 38 32 ft 22
KT 2.0 32 39° al 39 40 80GB AT 28
3.0 19 260287 48 42 Az AS 31 27
10 46 (388 87 at 308 33 AT 88
BI 20 AB OAT 38 39 36 40 35 29285
3.0 30 60 58 Bd 49 58 BS 38 27
10 46 (B68 40 82 34 31 32 19°28
Combined 2.0 40 43 37 39 8388 33 ot 38 26
3.0 24 4B 48 SL 48 AG 4988 32 28

The results of cross-modality matching with
dark-adaptation (Figures 1-4) reveal the possi-
bility of a Broca-Sulzer effect in the data of BJ
for the 97 dB comparison stimulus and in the
data of KT for the 86 dB comparison stimulus.
The high variability of the inter-modality data
could easily have masked small effects in this
condition or could have caused the deviations of
the single points just mentioned. The cross-
modality matching data for the light-adapted
condition (Figures 5-7) show a Broca-Sulzer
effect for BJ with the 97 dB comparison stimulus.
The minimum in the curve for KT at 500 msec.,
which involves displacement of only one point,
is probably due to response variability, as it is
beyond the range of durations in which the
maximum Broca-Sulzer effect occurs. The clear
hump in the curve for BJ is most likely an ap-
pearance of the Broca-Sulzer effect.

The results of the brightness-matching condi-
tions show a clear Broca-Sulzer effect for the
1000 mL. comparison stimulus in both the light-
adapted condition (Figures 8-11) and in the
dark-adapted condition (Figures 12-14).

The Broca-Sulzer effect is unequivocally present
only at the highest comparison stimulus level in
all instances. The minima of curves, indicating
a Broca-Sulzer effect, appear in every case at
the 50 and 100 msec. durations, Subject KT
consistently shows less effect than the other sub-
jects, but this does not seem to be due to her
data being more variable than that of the other
subjects,

The data of the cross-modality matching con-
ditions of this experiment indicate a Broca-

Sulzer effect for one subject with the effect
clearly attenuated in the dark-adapted condition.
This finding is in disagreement with a previous
study using cross-modality matching® in which
no Broca-Sulzer effect was obtained. The condi-
tions of the previous experiment were similar to
the dark-adapted inter-modality matching con-
dition of the current study and included the same
luminances. It appears that the carlier failure
to obtain the Broca-Sulzer effect may be due to
the inherently greater variability of cross-
modality matching data and possible attenuation
of the Broca-Sulzer effect in the dark-adapted
eye, this attenuation having previously been
noted by Baumgardt.°

The current experiment does confirm the ap-
pearance of the Broca-Sulzer effect with bright-
ness measurements not involving a visual
comparison stimulus, in agreement with the
studies of Raab’ and of Stevens and Hall.° Un-
like the inter-modality matching condition of the
current study, the Broca-Sulzer effect appeared
in the latter two studies with dark-adapted ob-
servers, An interaction between adaptive state
and method of measuring perceived brightness
in the determination of the Broca-Sulzer effect
may be indicated.

The intra-modality matching data in the dark-
adapted condition of the current experiment do
not show significant attenuation of the Broca-
Sulzer effect. The latter finding is in agreement
with Aiba and Stevens't who presented stimuli
under dark adaptation and at luminance levels
above and below the range of the present study.


35

3.0
a
E
B25
4

20

ro2 5 10 2 50 100 200 500 1000
t (msec)

Fiecre 7, Mean test flash luminance required for inter-
modality matches to three comparison stimulus
loudnesses as a function of test stimulus duration.
Data of both subjects in the light-adapted condition

are combined.
35

© 1.0 log mu
© 2.0 log mL
& 3.0 log mL

© 1.0 log mt
© 2.0 log mt
© 3.0 fog mt.

25p
25F

20

L (log mL)
L (log mL)

\ sh
1s
1.0
oF
1 A L A L oe yo
12 5 10 20 50 100 200 500 1000 2. 5 10 20 50 100 200 500 1000
t (msec) t (msec)

Fiecre 8 Mean test flash luminance required for an Ficcre 9, Mean test flash luminance required for an
jutrasmodality match to three comparison stimulus intra-modality match to three comparison stimulus
brightnesses as a function of test stimulus duration brightnesses as a function of test stimulus duration
for Subject BB in the dark-adapted condition, Each for Subject BJ in the dark-adapted condition, Each
mean represents 44 matches, mean represents 48 matches,


AM 68-27

ASSESSMENT OF THE BROCA-SULZER PHENOMENON
VIA INTER- AND INTRA-MODALITY MATCHING
PROCEDURES: STUDIES OF SIGNAL-LIGHT BRIGHTNESS

Mark F. Lewis, Ph.D.
Henry W. Mertens, M.A.

Approved by Released by
Bhat Ble (PU Sege€ ud
J. Rosert Ditre, M.D. P. V. Srecen, M.D.
Cuner, Crvi. AEROMEDICAL FeperaL Air SurGeon
INnstIruTE

October 1968

Department of Transportation

FEDERAL AVIATION ADMINISTRATION
Office of Aviation Medicine

24844


35
© 1.0 tog me
© 2.0 tog me
3.0 log mi
3.0
2.5
a
E
Py
&
Zaol
4
LS
10
2 5 10 20 50 100 200 500 1000
+ (msec)
Ficvre 14. Mean test flash luminance required for an
intra-modality match to three comparison stimulus

brightnesses as a function of test stimulus duration.
Data of both subjects in the light-adapted condition

i

cs

2

. STEVENS,

. Rass, D., FERRER,

. Srevens, J. C., and Harr, J. W.

are combined.

REFERENCES

S. S.: Concerning the measurement of

brightness. J. opt. soc, Amer., 56 :1135-1136, 1966.

. STEVENS, S. S.: Duration, luminance and the bright-

ness exponent. Percept. & Psychophys., 1:96-100,

1966,

, and HERSHENSON, M.: Visual

reaction time and the Broca-Sulzer phenomenon.

J. exp, Psychol., 61 :193-199, 19

. Lewis, M. F.: Category judgments as functions of

flash luminance and duration. J. opt. soc. Amer,

55 11655-1660, 1965.

. Raaw, D.: Magnitude estimation of the brightness

of brief foveal stimuli. Science, 135:

and
loudness as functions of stimulus duration. Percept.

& Psychophys. 1:96-100, 1966.

10

7. Lewis, M. F.: Category judgments and the luminance-

duration function. J. opt. soe. Amer. 56 21399-1400,

1966.

Lewis, M. F.: Cross-modality matching of loudness
to brightness for hes of varying luminance and

duration, Federal Aviation Administration Report

AM 67-16, 1967.

. Srevens, J. C., Mack, J. 1, and Srevens, 8, -S.:
Growth of sensation on seven continua as measured

we

2

by force of handgrip. J. erp. Psychol. 59 :60-67,

1960,
10, Bavaearpr, E.: Le phenomene de Broca et Sulzer
peripherique. @. R. Soe, Biol. (Paris).

and Str : Relation of bright
jon and luminance under light- and.
Vision Res., 4:391-401, 1964,

dur:
dark-adaptation,



35
© 1.0 Jog mL
© 2.0 tog mL
© 3.0 log mt
3.0
25h
a
E
4
er
Lob

L (log mL)

35h
© 1.0 tog mt
\ \ © 2.0 tog mt
3.0 tog me
3.0F
_o.
2.55 eo
\
20F
Sp
Lo

bo 5 10 20 50 100 200 500 1000
1 (msec)

Figure 12. Mean test flash luminance required for an
intra-modality match to three comparison stimulus
brightnesses as a function of test stimulus duration
for Subject BJ in the light-adapted condition. Each
mean represents 28 matches.

12 5 10 20 $0 100 200 $00 1000
t (msec)

Fievre 18, Mean test flash luminance required for an

intra-modality match to three comparison stimulus
brightnesses as a function of test stimulus duration
for Subject KT in the light-adapted condition, Each
mean represents 24 matches,



L (log mL)

Figvre 3.
modality

L (log mt)

Fievre 5.

35

RK

L (log mL)

2.0 2.0
1s 15
o 75 oB
© 86 48
2 97 aB
Lo 10
L 4 on 1
roe 5 10 20 0 100 200 500 1000 12 5 10 20 50 100 200 500 1000
1 (msec) 1 (msec)

Mean test flash luminance required for inter-

matches to three comparison stimulus
sas a function of test stimulus duration
ject KT in the dark-adapted condition, Each
mean represents 58 matches.

Figure 4.

Mean test flash Iuminance required for inter-
modality matches to three comparison stimulus
loudnesses as a function of test stimulus duration.
Data of the three subjects are combined.

3.5 asp
3.0 F 3.0
a
E
25F 3 ast
4
20F 2.0
2 5 10 20 50 100 200 500 1000 12 5 10 20 50 100 200 500 1000
t (msec) t (msec)

Mean test flash luminance required for inter-
modality matches to three comparison stimulus
loudnesses ax a function of test stimulus duration
for Subject BJ in the light-adapted condition. Each
mean represents 28 matches.

Fievre 6.

Mean test flash luminance required for inter-
modality matches to three comparison stimulus
loudnesses as a function of test stimulus duration
for Subject KT in the light-adapted condition. Each
mean represents 24 matches,



color vision defects. All were paid an hourly
wage. Data for one of the subjects (BB) are
available only for the dark-adapted conditions.

B. Apparatus. A three field optical system
was set up to deliver two adjacent 0.5° circular
stimuli to the fovea by Maxwellian view. The
stimuli were separated horizontally by approxi-
mately 0.2° in the field-of-view. In two of the
channels light from a Sylvania Glow Modulator
tube (R1131C) was collimated by one lens; an
image of the 2.36 mm. crater was focused in the
subject’s pupil by a second lens after the light
had passed through neutral density filters (Oriel
Optics) and neutral density wedges (Optical
Coating Laboratory) that were used to control
stimulus intensity, then through a field stop, and
a beam splitter. In the dark-adapted condition
the subject fixated, through the 3 mm. artificial
pupil, four red fixation lines provided through
the third field. In the light-adapted condition,
the tungsten source used in the fixation field was
replaced by a third Sylvania Glow Modulator
tube and the fixation lines were replaced with a
clear reticle with four fixation lines inscribed
upon it. Head position was controlled by a chin
and forehead rest. The glow modulator tubes
were driven by an Iconix light driver; the flash
durations were controlled by an Iconix 6257 time
base with preset controllers (Iconix 6010) and
associated logic. Flashes were monitored with
an RCA 1P21 photomultiplier tube operating
behind a Kodak Wratten 106 filter. Temporal
characteristics of the wave form of the light
flashes showed that, at the current level used
(40 mA.), rise time was less than Id5psec. and
decay time less than 25 psec. Luminance cali-
brations were made with a S. E. I. exposure
photometer by a method described earlier (Lewis.
1965).

Acoustic stimuli were generated by a Krohn-
Hite oscillator (model 440) and delivered mon-
aurally through a Western Electric headset
(#1002F) after passing through a Hewlett-
Packard model 350D attenuator set used to
control intensity.

C. Procedure. Fach session was preceded by

ten minutes of dark adaptation. Under the dark-
adapted condition the subject was then required
to adjust the intensity of the fixation lines until
the fixation lines were just visible. For bright-
ness matching conditions the comparison stimulus
was a 500-msec. flash of either 10, 100, or 1000
mL. Termination of the comparison flash was
coincident with termination of the test flash.
There were ten test flash durations ranging from
one to 1000 msec. The subjects adjusted the
brightness of the test flash to match the bright-
ness of the comparison flash by manipulating
with synchros a neutral density wedge in the
test field. The comparison stimulus always ap-
peared on the right and the test stimulus on the
left. For cross-modality matching, the compari-
son stimuli were 500-msec. presentations of a
1000-Hz tone whose intensity was either 97, 86,
or 75 dB SPL, these intensities calculated from
the data of Stevens, Mack, and Stevens’ to match
the luminance levels employed in the brightness
matching procedure. Subjects were instructed
to adjust the intensity of the test flash until it
was as bright as the tone was loud. On a single
trial, stimulus presentation occurred every 20
seconds in the dark-adapted condition and every
6 seconds in the light-adapted condition until
the subject was satisfied with his match. In the
Jight-adapted condition an adapting flash of 1.5
seconds duration was presented 2.5 seconds before
onset of the comparison flash on each trial; the
luminance of the adapting flash was identical
with the luminance of the comparison flash.

III. Results and Discussion.

The mean test flash luminance required to
match the comparison stimulus is plotted in
Figures 1-14 as a function of test flash duration
with luminance or loudness of the comparison
stimulus as the parameter, Standard deviations
of these matches are presented in Tables 1~4.
The data from cross-modality matches to the
75 dB and 86 dB comparison stimuli in the light-
adapted conditions were lost due to a technical
error in controlling the luminance of the light-
adapting field.


ASSESSMENT OF THE BROCA-SULZER PHENOMENON VIA INTER- AND
INTRA-MODALITY MATCHING PROCEDURES: STUDIES OF
SIGNAL-LIGHT BRIGHTNESS

I. Introduction.

The current study is directed toward evaluating
the effective brightness of signal lights for ob-
servers in aviation. Since signal lights are
usually presented to the observer as flashes with
finite duration, the effect of flash duration on
apparent brightness assumes importance. The
apparent brightness of a light flash of constant
supra-threshold luminance does not increase
monotonically with duration, but rather passes
through a maximum between 30 and 300 msec.
and then decreases about 2 dB to a steady
value.* This well known phenomenon, referred
to as the Broca-Sulzer effect, is typically meas-
ured using brightness matching procedures in
which subjects cither adjust the luminance of a
constant duration comparison stimulus to match
the brightness of test flashes which vary in dura-
tion, or adjust the luminance of test flashes of
varying duration to match the brightness of a
comparison flash of fixed duration and luminance.
Both procedures involve a visual comparison
stimulus.

Some experiments using techniques other than
brightness matching to measure perceived bright-
ness have not found the Broca-Sulzer effect.
Raab, Fehrer, and Hershenson* had three sub-
jects make category judgments of brightness to
flashes of constant luminance (3000 ft. L.) and
varying duration (10 to 500 msec.). No Broca-
Sulzer effect was observed. The authors hy-
pothesized that Broca-Sulzer maxima may occur
only when a visual comparison stimulus is pre-
sented along with the test flash and may not be
solely a function of flash duration. Lewis* had
two subjects make category judgments of bright-
ness to flashes of varying luminance and dura-
tion, Luminance of flashes ranged from 10 to
3000 mL. and durations from 0.2 to 260 msec.
No Broca-Sulzer effect was found.

Raab® did find the Broca-Sulzer effect when
eighteen subjects made magnitude estimates of
the apparent brightness of flashes whose lumi-
nance was between 0.035 and 100 mL. No effect
was noted, however, when luminance fell above
or below this range. Flash duration varied be-
tween 0.5 and 2000 msec. Stevens and Hall*
also interpreted their magnitude estimation data
indicating a Broca-Sulzer effect. Durations
used were 0.5 to 1000 msec. The effect appeared
in their study at Iuminances between 0.3 and
800 mL; however, no effect appeared with the
3000 mL. luminance. The negative finding of
Raab, Fehrer, and Hershenson. who employed a
similar high luminance is, thus, in agreement
with the results of the two studies just cited.
The results of these magnitude estimation studies,
as mentioned elsewhere,’ are not unequivocal,
however.

In a previous study.’ each of two subjects ad-
justed the intensity of a 1000 Hz tone presented
monaurally until he was satisfied that the tone
was as loud as the flash was bright. Stimuli
ranged in duration from 2 to 1024 msec., and in
luminance from 7.9 to 15.850 mL. The results
were interpreted as supporting the hypothesis
that the Broca-Sulzer effect may be obtained
only when a visual comparison stimulus is
presented.

The current study compares brightness func-
tions obtained using cross-modality matching
with those obtained with conventional procedures
in which a visual comparison stimulus is em-
ployed. These functions were obtained under
both dark-adapted and light-adapted conditions.

Il. Method.

A. Subjects, The three subjects (2 women and
a man) were undergraduates of the University
of Oklahoma. All were emmetropes with no


Qualified requestors may obtain Aviation Medical Reports from Defense Documentation
Center, The general public may purchase from Clearinghouse for Federal Scientific
and Technical Information, U.S. Dept. of Commerce, Springfield, Va. 22151.