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Reaction time as a function of retinal location
RESEARCH Reaction
U.S. I’ia\y
NOTE
time as a function of retinal
Electronics
LaborAtory,
(Received
San Diego,
4 Janunr~
location’
California
97151
1966)
IT HAS been concluded by POFFENBERCER (1912) that reaction time (RT) increases as the distance from the fovea increases along both directions on the horizontal meridian for a photopic stimulus. RAINS (1964) successfully replicated Poffenberger’s experiment. Between the two studies RTs at only 13 retinal locations on the horizontal meridian were investigated. It was the purpose of this study to investigate RT at a great number of points along several different meridians using four stimulus light intensities.
METHOD An American optical perimeter equipped with a lvhite fiberboard background illuminated at I.61 ml was used. The stimulus light subtended a visual angle of I ‘. The apparatus was later modified by using a black background and reducting stimulus light visual angle at I?‘. The apparatus was modified so that E could sample arbitrary points along a meridian (he was limited to multiples of 2-t” with the white background). The reduction in the stimulus size was to insure that totally different areas of the retina would be stimulated when using small, but greater than 12’, increments along a meridian. The stimulus light was produced by a Grass Photostimulator. Three levels of intensities of the stimulating light were used Lvith the apparatus with the white background. These intensities varied over a reasonably A single photopic stimulus large (about 1.5 log neutral density units) photopic range. intensity wxs used with the black-background apparatus. A fixed foreperiod (I .5 set) RI to the stimulus light was recorded on the paper tape of a Hewlett-Packard printer. 5 reacted to the stimulus by lifting a nail from a plate; if S felt he erred in response he \cas able to nulify it by depressing a key. The author, 25 yr of age with no known visual defects, ser\.ed as S. PROCEDlJRE
Twenty-four retinal locations were examined on each of four meridians using the I^ .4 counterbalanced experimental design stimulus light. Figure 1 gives the exact locations. with four running orders was used. Ten RTs were collected at each retinal location for each running order. Three stimulus intensities were run with this design along each of the four meridians. Next, using the modified apparatus, 33 retinal locations were investigated along the horizontal meridian, taking 60 RTs at each position except one. Two running orders 1 This study was done while the author was a NAS-NRC post-doctoral Research Associate under the sponsorship of Drs. C. T. White and R. G. Eason. The opinions and assertions contained herein are the private ones of the author. 729
FIG. I. The map of the subject’s retina showing where the RT data were gathered. The distance “a” was I.5 cm and the subject’s eye was located 30 cm from the perimeter. The RT data along meridians I, 2, 3, and 4 are given in Figs. 2 and 3.
SLOW
30
xl
NASA1 RETINA
IO
II0 OfGREG
10
20 TfMFORRl
30 RfilNI
FIG. 2. The plot of RT as a function of retinal location. The locations of the meridians arc seen in Fig. 1. The curves are offset for viewing clarity. The fovea1 RT for meridian 1 is 193 msec, 185 msec for meridian 2, and 183 msec for meridian 3. Each data point on the graph is based on 120 RTs. A white backgro~lnd ilfuminated by I41 mi and averaged data for three stimulus intensities were used in obtaining each plot.
Reaction
Time as a Function
of Retmal
Location
731
retinal used (30 RTr taken at each point on each order) so that running order location differences could be tested. Ten RTs at 1’ on the temporal retina lvere taken after each 30 RTs. This Leas done to test changes in RT over long periods of time.
tverz
RESULTS
The results are graphically given means (estimated from error terms meridian 7, 3.75 msec; and meridian standard deviation is 3.32 msec and order or time of data collection were
in Figs. 2 and 3. The standard deviations of the RT of analyses of variance) are meridian 1. 3.19 msec: 3, 4.49 msec, for Fig. I. For Fig. 2, meridian 4, the 4.32 msec for meridian 2. No differences in running found.
,
r
I
I
I
0 MtRlOlln4
A MtRlOlliN 2
NASAL RETINA
TEMPORAL
RETINA
OtGREIS
FIG. 3. The plor of RT as a function of retinal location along meridians 2 and 4. The t\+o curves are offset for viewing clarity. The fovea1 RT for meridian 2 is 192 msec and 190 msec for meridian 4. Each data point for meridian ? is based on I’70 RTs. The meridian Z data were based on 60 RTs except for circled point where there were 640 RTs. The RTs along meridian 1 were gathered under the same conditions as those in Fig. I (seecaption. Fig. I). .+. black background illuminated by I.61 ml and a single stimulus intensity were used in collecting the RTs along meridian 1.
DISCGSSIOS
The limited data gi\.en in the earlier studies on RT LS. retinal localion are misleading. The conclusion that RT increases directly with the distance from the fovea along the horizontal meridian is unwarranted, in view of the present data. Rather, there is a decrease in RT at the point along the horizontal meridian where the sum of the rods and cones is mosr numerous (i.e. 17”), as plotted by ~STERBERG (1935). The minimum RT not at the fo~sa. occurs on the retinal area corresponding to the blind spot of the other eye. Otherwise, these data are completely compatible with the Rains and PoEenberger data: only the additional points investigated here change their conclusion. The RTs along the 45-225” meridian do not resemble those collected along the horizontal meridian. These curves can be obtained under a wide variety of stimtllating cond~tjons. It is only important that the stimulus not be excessively bright or very dim (see RAINS, 1964). REFERENCES ~STERBEKG, G. (1935). Topography of the layer of rods and cones in the human retina. .-tc~n opithzl. Suppl. 6, l-102. POFFENBERGER,A. T. (1912). Reaction time to retinal stimulation with special reference to time lost in conduction through nerve centers. Arc/~ fqA_~l., N. 1.. 3, 23, l-73. RMNS, J. D. (1944). Signal luminance and position effects in human reaction time. Vis:isiut~ lies. 3, 239-251.
U.S. I’ia\y
NOTE
time as a function of retinal
Electronics
LaborAtory,
(Received
San Diego,
4 Janunr~
location’
California
97151
1966)
IT HAS been concluded by POFFENBERCER (1912) that reaction time (RT) increases as the distance from the fovea increases along both directions on the horizontal meridian for a photopic stimulus. RAINS (1964) successfully replicated Poffenberger’s experiment. Between the two studies RTs at only 13 retinal locations on the horizontal meridian were investigated. It was the purpose of this study to investigate RT at a great number of points along several different meridians using four stimulus light intensities.
METHOD An American optical perimeter equipped with a lvhite fiberboard background illuminated at I.61 ml was used. The stimulus light subtended a visual angle of I ‘. The apparatus was later modified by using a black background and reducting stimulus light visual angle at I?‘. The apparatus was modified so that E could sample arbitrary points along a meridian (he was limited to multiples of 2-t” with the white background). The reduction in the stimulus size was to insure that totally different areas of the retina would be stimulated when using small, but greater than 12’, increments along a meridian. The stimulus light was produced by a Grass Photostimulator. Three levels of intensities of the stimulating light were used Lvith the apparatus with the white background. These intensities varied over a reasonably A single photopic stimulus large (about 1.5 log neutral density units) photopic range. intensity wxs used with the black-background apparatus. A fixed foreperiod (I .5 set) RI to the stimulus light was recorded on the paper tape of a Hewlett-Packard printer. 5 reacted to the stimulus by lifting a nail from a plate; if S felt he erred in response he \cas able to nulify it by depressing a key. The author, 25 yr of age with no known visual defects, ser\.ed as S. PROCEDlJRE
Twenty-four retinal locations were examined on each of four meridians using the I^ .4 counterbalanced experimental design stimulus light. Figure 1 gives the exact locations. with four running orders was used. Ten RTs were collected at each retinal location for each running order. Three stimulus intensities were run with this design along each of the four meridians. Next, using the modified apparatus, 33 retinal locations were investigated along the horizontal meridian, taking 60 RTs at each position except one. Two running orders 1 This study was done while the author was a NAS-NRC post-doctoral Research Associate under the sponsorship of Drs. C. T. White and R. G. Eason. The opinions and assertions contained herein are the private ones of the author. 729
FIG. I. The map of the subject’s retina showing where the RT data were gathered. The distance “a” was I.5 cm and the subject’s eye was located 30 cm from the perimeter. The RT data along meridians I, 2, 3, and 4 are given in Figs. 2 and 3.
SLOW
30
xl
NASA1 RETINA
IO
II0 OfGREG
10
20 TfMFORRl
30 RfilNI
FIG. 2. The plot of RT as a function of retinal location. The locations of the meridians arc seen in Fig. 1. The curves are offset for viewing clarity. The fovea1 RT for meridian 1 is 193 msec, 185 msec for meridian 2, and 183 msec for meridian 3. Each data point on the graph is based on 120 RTs. A white backgro~lnd ilfuminated by I41 mi and averaged data for three stimulus intensities were used in obtaining each plot.
Reaction
Time as a Function
of Retmal
Location
731
retinal used (30 RTr taken at each point on each order) so that running order location differences could be tested. Ten RTs at 1’ on the temporal retina lvere taken after each 30 RTs. This Leas done to test changes in RT over long periods of time.
tverz
RESULTS
The results are graphically given means (estimated from error terms meridian 7, 3.75 msec; and meridian standard deviation is 3.32 msec and order or time of data collection were
in Figs. 2 and 3. The standard deviations of the RT of analyses of variance) are meridian 1. 3.19 msec: 3, 4.49 msec, for Fig. I. For Fig. 2, meridian 4, the 4.32 msec for meridian 2. No differences in running found.
,
r
I
I
I
0 MtRlOlln4
A MtRlOlliN 2
NASAL RETINA
TEMPORAL
RETINA
OtGREIS
FIG. 3. The plor of RT as a function of retinal location along meridians 2 and 4. The t\+o curves are offset for viewing clarity. The fovea1 RT for meridian 2 is 192 msec and 190 msec for meridian 4. Each data point for meridian ? is based on I’70 RTs. The meridian Z data were based on 60 RTs except for circled point where there were 640 RTs. The RTs along meridian 1 were gathered under the same conditions as those in Fig. I (seecaption. Fig. I). .+. black background illuminated by I.61 ml and a single stimulus intensity were used in collecting the RTs along meridian 1.
DISCGSSIOS
The limited data gi\.en in the earlier studies on RT LS. retinal localion are misleading. The conclusion that RT increases directly with the distance from the fovea along the horizontal meridian is unwarranted, in view of the present data. Rather, there is a decrease in RT at the point along the horizontal meridian where the sum of the rods and cones is mosr numerous (i.e. 17”), as plotted by ~STERBERG (1935). The minimum RT not at the fo~sa. occurs on the retinal area corresponding to the blind spot of the other eye. Otherwise, these data are completely compatible with the Rains and PoEenberger data: only the additional points investigated here change their conclusion. The RTs along the 45-225” meridian do not resemble those collected along the horizontal meridian. These curves can be obtained under a wide variety of stimtllating cond~tjons. It is only important that the stimulus not be excessively bright or very dim (see RAINS, 1964). REFERENCES ~STERBEKG, G. (1935). Topography of the layer of rods and cones in the human retina. .-tc~n opithzl. Suppl. 6, l-102. POFFENBERGER,A. T. (1912). Reaction time to retinal stimulation with special reference to time lost in conduction through nerve centers. Arc/~ fqA_~l., N. 1.. 3, 23, l-73. RMNS, J. D. (1944). Signal luminance and position effects in human reaction time. Vis:isiut~ lies. 3, 239-251.