The Effect of Area, Density, and Number of Background Characters on Visual Search

In a search task, area of search field, density of background characters, and number of background characters are not independent. Many authors have found increases in search times with each of these factors but have not adequately controlled all three together. In this experiment, eight subjects searched a set of search fields covering combinations of all three variables. Search time was found to depend most heavily on number of background characters, but there were significant effects due to the other two variables. For a constant number of background characters, search time decreases as density increases. Direct visual lobe measurements confirmed these findings, which could have importance in visual inspection tasks.