Using visual-analogue scales in E-prime

[Kai]

Dear e-prime users,

Using e-prime, we are trying to program a 20-item questionnaire with
visual-analogue scales (VAS) for the responses. This will require the
movement of an arrow along a line (from 0 to100 percent) in response to
the question; e. g., the stimulus “Do you feel tired ?” would be
presented at the top of the screen, and below would be presented a 0-100
percent response line (with labeled endpoints) and a moveable arrow. The
subject would move the arrow back and forth along the line (preferably
by using the SRBox keys no 1 and 5) in order to fine-tune its position
until it is perceived as represntative for his/her current state. The
subject would then confirm/enter this response by pressing a separate
key, and the next question would appear (and so on).

Problem: We are able to achieve the movement of an arrow along a line,
but only by setting up each small step of arrow movement (i. e. each
key-press) as a separate reaction time (RT) stimulus-response (S-R). But
this leads to serious problems: If the scale resolution is set to 2
percent (0-100% = 50 steps), already moving along the scale once leads
to 50 RT S-R:s. Together with some margin for additional movements, the
number of RT:s must reasonably be set to at least 300 for each question!
This would of course make a 20-item questionnaire extremely large (not
to mention the enormous amount of unwanted data obtained). Obviously
this approach is incorrect. We have not succeeded to solve the riddle of
how make the arrow move back and forth along the VAS-scale in response
to keyboard inputs without making e-prime believe that each arrow
movement represents a RT S-R event. The only two response data of
interest to us is the position of the arrow when the subject makes his
FINAL confirmatory key-press and the decision time.

We would welcome any suggestion of how to properly program this type of
VAS-question within e-prime.

Thanks,

Kai Österberg, PhD
Dept. Occupational and Environmental Medicine
Lund University
SE-22185 Sweden

kai.osterberg at ymed.lu.se
phone +46-46-177292