Journal of Experimental Psychology 1968, Vol. 78, No. 2, 344-346
SUPPLEMENTARY
REPORTS
EFFECT OF EAR STIMULATED ON REACTION TIME AND MOVEMENT TIME J. RICHARD SIMON 1 University of Iowa
In a unimanual choice RT task, 5s moved a control handle to the right or left from the midline of the body in response to monaural verbal commands of "right" or "left" which were presented to the right or left ear. Both RT and MT were significantly faster when the content of the command corresponded to the ear stimulated than when it did not; i.e., the time required to initiate and execute the movement was affected by a cue irrelevant to the task itself, the ear in which the command was heard. RT was faster for abductive movements toward the side of the responding member whereas MT (for the right hand) was faster when movements were directed toward the opposite arm. In a recent experiment, Simon and Rudell (1967) noted a potent population stereotype which affected reaction time (RT) to verbal directional commands. Their 5s pressed a right- or left-hand key in response to the commands "right" or "left" which were presented to the right or the left ear. RT was significantly faster when the content of the command corresponded to the ear stimulated (i.e., right in the right ear or left in the left ear) than when it did not (i.e., right in the left ear or left in the right ear). In other words, information processing was affected by a cue irrelevant to the task itself, the ear in which the command was heard. The present study was designed to determine whether the above-mentioned stereotype is specific to a bimanual task or whether it is also present in a unimanual task involving the movement of a lever to the right or left. If the former were true, it would suggest that the stereotype derives from a simple isomorphic association of right-ear stimulation with a right-hand response and left-ear stimulation with a left-hand response. If the latter were true, it would suggest that the stereotype is a manifestation of a more basic orienting reflex; i.e., a reaction toward the source of stimulation (Razran, 1961). This study was also concerned with determining whether the stereotype in question affected movement time (MT) as well as RT. 1 The author acknowledges the assistance of Philip Tolin in collecting the data.
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Method.—The 5s" task was to move a control handle to the right or left from a center position in response to a recorded series of 132 commands used previously (Simon & Rudell, 1967). Each command consisted of the words right or left and was presented through earphones to the right or the left ear in a predetermined random sequence. A klockounter which recorded RT started when a command was presented and stopped when S moved the handle away from the center position. Another klockounter which recorded MT started when the handle had been moved from the center position and stopped when the 10-in. lateral movement had been completed. The 5s were instructed to "react and move as fast as you can on each trial." The 5s were 32 male and 32 female undergraduates. All were righthanded. Half of the males and half of the females performed with their right hand while the other half of each group performed with their left hand. Results.—Median RTs and MTs were computed for each 5 for each of the four experimental conditions; i.e., right and left commands in the right and in the left ear. The left half of Table 1 summarizes the mean RT under each treatment condition for the right- and left-hand groups. Analysis of variance revealed no differences as a function of the main effects of ear stimulated, command, or responding member. There was, however, a significant difference between the sex groups, F (1, 60) =7.69, p < .01, with males responding significantly faster than females (377 vs. 419 msec.).
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SUPPLEMENTARY REPORTS TABLE 1 REACTION TIME AND MOVEMENT TIME (MSEC.) TO VERBAL COMMANDS AS A FUNCTION OF EAR STIMULATED AND RESPONDING MEMBER
Responding Member
Ear Stimulated
Reaction Time
Movement Time
Command
Command
Right
Left
M
Right
Left
M
Right- (Preferred) Hand Group
Right ear Left ear M
365 401 383
415 376 395
390 389 389
182 183 183
169 166 168
175 175 175
Left- (Nonpreferred) Hand Group
Right ear Left ear M
392 426 409
424 384 404
408 405 407
166 169 167
168 166 167
167 168 167
Right- and Left-Hand Groups Combined
Right ear Left ear M
378 414 396
420 380 400
399 397 398
174 176 175
168 166 167
171 171 171
The analysis also revealed a significant Command X Responding Member interaction, F (1, 60) =7.11, p < .01. Table 1 shows that the right-hand group reacted faster to the right command than to the left command (383 vs. 395 msec.) whereas the lefthand group reacted faster to the left command than to the right command (404 vs. 409 msec.). This interaction is probably due to the nature of the reaction required to respond to the command. Both the right reaction with the right hand and the left reaction with the left hand involved an abductive movement (from the midline of the body) toward the same side as the responding member. In contrast, the left reaction with the right hand and the right reaction with the left hand involved an abductive movement toward the opposite arm. The major finding was a significant Command X Ear Stimulated interaction, F (1, 60) = 179.69, p < .001. This effect is pictured in the left half of Fig. 1. It will be noted that RT to the right command was faster when it was heard in the right ear than when it was heard in the left ear (378 vs. 414 msec.) and, similarly, RT to the left command was faster when it was heard in the left ear than when it was heard in the right ear (380 vs. 420 msec.). Analysis of responses of individual 5s revealed that the difference between right and left ear responses was in the predicted direction in 117 out of 128 separate comparisons. The right half of Table 1 summarizes the mean MT under each treatment condition for the right- and left-hand groups. Analysis of variance revealed that movements to the left were significantly faster than movements to the right (167 vs. 175 msec.), F ( I ,
60) = 30.99, p < .001. Inspection of Table 1 reveals, however, that this difference appeared only in the right-hand group, Command X Responding Member interaction, F (1, 60) =28.18, P< .001. The analysis also indicated that males moved significantly faster than females (158 vs. 184 msec.), F (1, 60) =6.75, p < .05. The other main effects, ear stimulated and responding member, were not significant. Of perhaps greatest interest was the significant Command X Ear Stimulated interaction, F (1, 60) =10.49, p < .01. The right half of Fig. 1 shows that movements to the right were faster when the right command was heard in the right ear than when it was heard in the left ear. Similarly, movements to the left were faster when the left command was heard in the left ear than when it was heard in the right ear. Though the differences between the means were small, the direction of the differences was in the hypothesized direction in 75 out of 128 comparisons with seven ties. This relationReaction Time
Movement Time
430 „_-» RIGHT COMMAND •—• LCFT COMMAND
420 410
o **0o
ISO -
V
A
o
SJ 390
/
I 380
J
\
170
\
ISO
•^
.
-
150 -
370 1
RIGHT EAR LEFT EAR EAR
RIGHT EAR LEFT EAR STIMULATED
Fio. 1. Effect of ear stimulated on RT and MT.
346
SUPPLEMENTARY REPORTS
ship was observed in both right- and lefthand groups but was more marked for males than for females-—Command X Ear Stimulated X Sex interaction, F (I, 60) = 6.62, p < .05. Discussion.—Results of the present study indicated that the speed of processing directional commands (i.e., the words right and left) was affected by an irrelevant cue; that is, the ear in which the command was heard. RT to right in the right ear was faster than to right in the left ear, and, similarly, RT to left in the left ear was faster than to left in the right ear. These results, obtained on a unimanual task, paralleled those noted by Simon and Rudell (1967) on a bimanual task. Another notable result was that MT was also affected by the ear in which the command was heard, movements being faster when the content of the command corresponded to the ear stimulated than when it did not. Whereas the literature contains numerous examples of display characteristics affecting RT, there are apparently few, if any, examples of display characteristics affecting the rate of a ballistic movement once it has been initiated (McCormick, 1964). The response interference observed in the present studies to date is, apparently, unrelated to sensory motor connections or hemispheric dominance since there is no interaction between ear stimulated and handedness (Simon & Rudell, 1967), and there is also no interaction between ear stimulated
and responding member on either unimanual or bimanual tasks. Initially, it appeared that the interference was due to a strong natural tendency to associate rightear stimulation with a right-hand response and left-ear stimulation with a left-hand response. Indeed, in a bimanual key-pressing task with monaural pure tones as stimuli, 6"s responded faster on blocks of trials involving uncrossed reactions (responding with hand ipsilateral to ear stimulated) than they did on trials involving crossed reactions (responding with hand contralateral to ear stimulated) (Simon, 1967). Obviously, however, the interference observed in the present study (a unimanual task) cannot be explained on the basis of a simple isomorphic association between ear stimulated and ipsilateral hand. It may, instead, be a manifestation of the more basic orienting reflex (OR) which, in its fully developed form, can involve a specific molar reaction of turning toward the source of stimulation (Razran, 1961). REFERENCES McCoRMlCK, E. J. Human factors engineering. (2nd ed.) New York: McGraw-Hill, 1964. RAZRAN, G. The observable unconscious and the inferable conscious in current Soviet psychophvsiolpgy: Interoceptive conditioning, semantic conditioning, and the orienting reflex. Psychological Review, 1961, 68, 81-147. SIMON, J. R. Choice reaction time as a function of auditory S-R correspondence, age and sex. Ergonomics, 1967, 10, 659-664. SIMON, J. R., & RUDELI, A. P. Auditory S-R compatibility: The effect of an irrelevant cue on information processing. Journal of Applied Psychology, 1967, 61, 300-304. (Received July 28, 1967)
