2.2 Pilot Study

A total of six subjects were tested for the pilot study (one per treatment), whose experience levels ranged from an occasional user to an expert one. Prior to testing our own image browsing program, a very preliminary pilot study (using a commercially available image browsing program) was conducted to get a feel of how long it would take to visually search a database of 176 images. After confirming that a search of this scope would be reasonable we went ahead and tested out our custom program. The mean time to find an image was about 80 seconds. 17 seconds was the fastest time and 255 seconds was the slowest.

While this is only a pilot study, we did make a very interesting observation that due to the high similarity of the images, parallel visual processing was nearly impossible. We noticed that for both the button and scrollbar implementations, the subjects would often pass over the target image at least once (i.e. subjects tended to try to process the information in parallel). However, for the velocity-slider implementation, the nature of the automatically scrolling images forced a sort of serial processing. Thus while the rate of scrolling was on average, slower than the other two implementations, subjects seemed more likely to recognize the target image upon encountering it for the first time.

The following changes were made to the original experiment design:

  • Our original design was to have a 1x1 grid and a 5x5 grid of images as one of the independent variables. Due to other material we have examined (e.g. Chris North's paper) we have decided to change the 1x1 grid to a 3x3 grid. Additionally, the 1x1 grid caused a number of implementation and resource problems. 176 BMP format images at 512x512 resloution requires well over 30 megs of space, which causes all kinds of memory and transportation problems.

  • The original design also called for a modal dialog box to appear whenever an incorrect image was selected. We found this distracting and problematic (we had to cover all the images while the box appeared, and timing issues arose as well), so instead the same message will appear on the screen in a consipcuous place so as to inform the subject of the mistake with minimal distraction.