Reaction, movement, and task times refer to the times needed to initially respond to a stimulus, make the specific movement, and complete the entire task. This study evaluated the reliability of a simple reaction timer designed to mimic a Space Shuttle task (turning on an overhead switch)

Hays, Russell D.

Mazzocca, Augustus D.

Rashid, Michael

Siconolfi, Steven F.

English

NASA Technical Reports Server

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Technical
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3176
January 1992
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Reliability of
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Russell D. Hays,
Augustus D. Mazz0cca,
Michael Rashid,
and Steven Siconolfi
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NASA
Technical
Paper
3176
1992
National Aeronautics and
Space Administration
Office of Management
Scientific and Technical
Information Program
Reliability of
a "Shuttle"
Reaction Timer
Russell D. Hays
and Augustus D. Mazzocca
KRUG Life Sciences
Houston, Texas
Michael Rashid
and Steven Siconolfi
Lyndon B. Johnson Space Flight Center
Houston, Texas
± ;
ABSTRACT
Reaction, movement, and task times refer to the times needed to
initially respond to a stimulus, make the specified movement, and
complete the entire task. These three times can characterize the
function of a neuromuscular circuit. This study evaluated the
reliability of a simple reaction timer designed to mimic a Shuttle task
(turning on an overhead switch). A "Shuttle" reaction timer was
designed in which a joystick rested between the subject's legs and a
Shuttle switch was mounted overhead. The stimulus was presented
both visually and audibly. A monitor that was placed in the subject's
visual field displayed scenes of spacecraft and airplanes. Reaction
and movement times were recorded by a computer. Task time was
the sum of the reaction and movement times. Ten subjects were
given an orientation session to the instrument and then completed 2
blocks of 25 trials on each of the next 3 days. For each block of trails
on the 3 days, the 25 trials for each subject were averaged to
provide a single measure of reaction time. Intraclass correlation and
a 2x3 repeated measures ANOVA were used to evaluate the
reliability and to test for differences in mean reaction time. Mean
(SD) reaction times in msec are shown below:
Day 1 Day 2 Day
Block 1 291 (35) 276 (30) 263 (24)
Block 2 286 (40) 270 (36) 265 (18)
Neither the means across days nor the means between blocks were
significantly different. The intraclass correlation was 0.908. The
Shuttle reaction timer is a reliable means of measuring reaction time.
The timer may be used to evaluate the effects of muscle
deconditioning on reaction, movement, and task times.
INTRODUCTION
Changes in reaction and movement times as a result of long-term
space flight could pose a potentially hazardous situation during entry
and landing. To date, very little research has been conducted
examining the effect of space flight on reaction and movement time.
Reaction and movement times refer to the time required to initially
respond to a stimulus and to make the specified movement. Task
time refers to the summation of these two times.
Clement, et al. (2) observed no changes in the reaction time of an arm
flexion motion following a seven-day space flight (n = 2). Reaction
time was measured as the time elapsed between initiation of the
auditory stimulus and the earliest detectable change in the arm
accelerometric signal. Movement and task times were not reported.
The need for further studies is warranted because of the apparent
limitations in sample size. An alternative to actual space flight would
be to study the effects of simulated microgravity on reaction, move-
ment, and task times.
Simplistic motions, such as elbow flexion, are often used as a model
for evaluation of reaction and movement time. It has been shown
that simple reaction time (SRT) increases as the response becomes
more complex (1). Most operational tasks on the Shuttle are made
up of complex movements. The evaluation of reaction, movement,
and task times for an operational task is, therefore, needed. A
reaction timer was constructed to simulate such a task. The scenario
of a pilot turning on an overhead switch was chosen as a task vital to
the safe entry and landing of the spacecraft. The purpose of this
study was to determine the reliability of a newly designed reaction
timer which could fractionate complex task times into reaction time
(time elapsed between visual/auditory stimuli and initiation of
movement) and movement time (time elapsed between initiation of
movement and turning on the overhead switch).
METHODS
Construction. A reaction time measurement system (RTMS) was
constructed to study the effects of simulated microgravity on human
reaction time. This system was designed and built to operationally
mimic the Shuttle pilot position and to establish and implement
certain test protocols utilizing the various Shuttle display and control
apparatus. The particular display and control devices utilized in the
tests were the flight control joystick, the main panel alarm indicator,
and the overhead control panel (Figure 1).
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Figure 1 - Reaction Timer
The flight joystick was utilized to provide an accurate starting
position of the subject's hand. The visible main panel alarm
indicator, in conjunction with an audible alarm, was used as the
subject stimulus, and the overhead control panel provided the target
switch for the subject to actuate after being stimulated. A monitor
was placed above the main panel and below the overhead panel so
that scenes of space and air flight could be displayed.
A single chip microcontroller unit (MCU) and associated electronic
interface circuitry was constructed to measure reaction time during
this complex movement. The interface circuitry was designed to
allow the MCU to control the activation of the audible and visual
stimuli, to monitor the position of the test subjects' switches and
operating control selectors, and to permit interconnection of the MCU
and a host computer system. The subjects' switches were located in
the flight joystick and on the overhead panel. Computer software for
satisfaction of the test protocol was written and transferred
permanently to the MCU. The time base was derived from a high
stability, four megahertz, crystal oscillator contained within the MCU
that enabled event timing accuracy to within + 1 millisecond. The
3
MCU measured reaction, movement, and task times.
were recorded and saved to a host computer.
These times
Protocol. Ten subjects were given an orientation session to
familiarize themselves with the instruments and procedures.
Subjects were seated at arm's length from the overhead control
panel. The height of the joystick, control panel, and chair remained
constant for all individuals. Subjects sat i_the chair with a
restraining strap placed across the right shoulder. Reaction time was
assessed using the right arm of all subjects. Initiation of a trial
began when the subject depressed the joystick trigger. The
visual/auditory stimulus occurred randomly between one and four
seconds after depressing the trigger. Subjects responded to the
stimulus by activating the specified switch on the overhead control
panel. A monitor displaying space and aviation scenes was placed in
the subject's visual field to provide competing information that
would normally be present during entry and landing of the Shuttle.
All ten subjects completed two blocks of 25 trials over the next three
days, with the two blocks being separated by a two minute rest
period. Reaction and movement times were recorded and saved to a
host computer. For each block of trials during the three days, the 25
trials for each subject were averaged to provide a single measure of
reaction time. Statistical analysis included an intraclass correlation
and a 2x3 (blocks of trials versus days of testing) repeated measures
analysis of variance to determine mean differences in reaction time.
DISCUSSION
The accuracy of the reaction timer hardware can be attributed to the
single chip microcontroller unit that controls the activation of the
stimuli, monitors position of the switches, and transfers results
obtained to a host computer system. Elapsed time is accurate to
within _+ 1 millisecond due to the four megahertz, crystal oscillator
contained in the microcontroller unit.
Reaction and movement times can provide valuable information
pertaining to a skilled motor performance. Reaction time can be
affected by a variety of factors including fatigue (4), repetition of
stimuli (3), task complexity (1), and sensory modaIity employed (5).
The effects of microgravity on reaction and movement times require
evaluation. Decrements in skilled motor performance during
extended space flight may pose serious problems to the successful
4
completion of a mission. The reaction timer described in the present
study was constructed to initiate studies evaluating the effects of
microgravity on components of skilled motor performance. Before
such studies could proceed, however, it was necessary to assess the
reliability of the reaction timer.
The present study demonstrated that reaction time of a complex
movement can be performed consistently over several days. It is
well accepted that the greater the complexity of the task, the greater
the reaction time (1). The present study demonstrated a significant
correlation over blocks and days despite the increased complexity of
the task. This indicates that the reaction timer described can be used
to reliably assess possible changes in reaction time incurred by
simulated or actual microgravity.
RESULTS
Analysis of variance indicated no significant differences between
means over the three days of testing (Figure 2).
350
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._ 250
_ 2000
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150
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Figure 2
[] Block 1
I! Block 2
2
Days
i
Reaction Time
3
Intraclass correlation provided a value of 0.908. These results
indicate that the reaction timer can be used as a reliable and
consistent means of assessing reaction time.
REFERENCES
1. Christina, R. W., Fischman, M. G., Vercruyssen, M. J. P., and Anson,
J.G. Simple reaction time as a function of response complexity:
Memory drum theory revisited. J. Motivat. Behav. 14(4):301-21,
1982.
2. Clement, G., Gurfinkle, V. S., Lestienne, F., Lipshits, M. I., and
Popov, K.E. Changes of posture during transient perturbations in
microgravity. Aviat. Space Environ. Med. 56(7):666-71, 1985.
3. Mowbray, G. H. and Rhoades, M. V. On the reduction of choice
reaction times with practice. Quart. J. Exp. Psych. 11:16-23, 1959.
4. Muto, W. H. and Wierwille, W. W. The effect of repeated
emergency response trials on performance during extended duration
simulated driving. Human Factors 2:693-698, 1982.
5. Sheridan, T. B. and Ferrell, W. R. Man-Machine Systems-
Information, Control, and Decision Models for Human Performance.
Massachusetts: MIT press, 1974.
6


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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE
January 1992
' 41 TITLE AND SUBTITLE 5. FUNDING NUMBERS
Reliability of a "Shuttle" Reaction Timer
3 REPORTTYPEAND DATESCOVERED
Technical Paper
6 AUTHOR(S)
Russell D. Hays, Augustus D. Mazzocca, Michael Rashid, and
Steven Siconolfi
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES}
Medical Sciences Division
Space Biomedical Research Institute
National Aeronautics and Space Administration
Johnson Space Center
Houston, Texas 77058
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National Aeronautics and Space Administration
Washington, D.C. 20546-001
8. PERFORMING ORGANIZATION
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S-659
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NASA TP-3176
11. SUPPLEMENTARYNOTES
R. D. Hays and A. D. Mazzocca IKRUG Life Sciences, Houston, Texas)
M. Rashid and S. F. Siconolfi (NASA Johnson Space Center, Houston, Texas)
12a. DISTRIBUTION / AVAILABILITY STATEMENT
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13. ABsrRACT (Maximum 2OO word$)
Reaction, movement, and task times refer to the times needed to initially respond to a
stimulus, make the specified movement, and complete the entire task. These three times
can characterize the Function of a neuromuscular circuit. This study evaluated the
reliability of a simple reaction timer designed to mimic a shuttle task (turning on an
overhead switch).
M. SUBJECTTERMS
Reaction time, movement time, task time, and reaction timer
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Reliability of a Shuttle reaction timer

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