User`s guide

E-Prime User’s Guide
Appendix B: Considerations in Research
Page A-24
Familiarizing subjects with the situation
Especially with computerized experiments, it is sometimes necessary to spend time making sure
subjects are comfortable, because they need to do the experimental task without being distracted
by the surroundings. Many researchers rely on undergraduates as subjects, and can assume a
familiarity with computers. However, in an elderly population, the subjects may not be familiar
with computers. In research with psychiatric patients, a strange situation may significantly alter
the subject’s ability to comprehend and focus on the experimental task. Giving a session of
practice just to overcome the threat of a new, strange environment may be well worth the extra
time and trouble. Research with children introduces other problems, such as understanding
instructions. The use of a response box with just a few keys might be helpful in some of these
situations by reducing the distractions inherent in a computer keyboard with its 100+ keys.
If data collection will take place on a computer other than the one used for setting up the
experiment, be sure the pilot testing is done on the computer to be used for the final experiment.
Problems that can arise include differences in display sizes, as well as problems of switching to a
different graphics adapter.
Where will data collection take place?
Give some prior consideration to the setting for data collection. Most often, this is done with one
subject at a time, in a laboratory setting. Sometimes, however, the data collection may take place
in a hospital or clinic, or another setting.
Considerations in regard to the location of the laboratory include:
Limiting outside noise and interruptions. If tests must be done in a noisy environment, it may
help to use a white-noise generator being played over a speaker or headphones to block most
extraneous sounds. If several subjects are tested at once, it helps to have dividers or separate
booths, since this discourages the subjects from chatting among themselves.
Control of lighting. Glare on the computer monitor is sometimes a problem, especially in a
relatively dimly lit room. This can be a major problem when using brief, data-limited displays.
Adjust the position of the monitor to eliminate glare. Also adjust the brightness and contrast so
that the display is clear and sharp. Note that a display seen in a brightly lit room may look too
bright (and fuzzy) when the lights are dimmed.
Control of access to the computer. It is a good idea to place the computer itself where the
subject cannot reach the controls (i.e., so that they do not reboot the machine, pop out a floppy
disk, or adjust the monitor settings).
Comfort. If subjects must sit for lengthy experimental sessions, be sure to have a comfortable
chair. A few minutes spent adjusting the chair for a tall or short subject may reduce their
discomfort considerably. Ambient temperature should also be comfortable.
Testing multiple subjects. If several computers are available, consider testing several subjects
at once. Verbal instructions can be used if all subjects start at the same time, but if they do not,
maybe have all instructions on the screen. If so, be sure to test those instructions thoroughly
beforehand—instructions that were thought to be perfectly clear may not be for the subject
population. Another consideration for multiple-subject testing arises when using auditory
presentation of stimuli or tones to signal error trials. Subjects can easily be confused about
where the sounds are coming from; however, headphones can usually avoid that problem.