The Effects of Legibility and Display Size on Performance for RAPCOM and Spatial Display Formats

Abstract

Information formatting in terms of optimal spatial and temporal parameters has become an important issue with the advent of computer automated displays. One temporal format involving sequential presentation of information, termed RAPCOM (for rapid comunication; cf., Matin and Boff, 1988), has the potential to increase performance in situations involving high information transfer rates. The present study investigated the relative contributions of two spatial parameters comparing RAPCOM with more conventional spatial formats involving simultaneous presentation of information. The parameters of character size and spatial separation were examined because they are important determinants of display legibility and visual search, respectively. Performance was assessed in terms of speed and accuracy for a task that required observers to recall integers presented in either an analog or digital format. The findings showed that accuracy performance decreased as the information became spatially separated. Specifically, RAPCOM formats produced the best performance and the large spatial separation the worst performance. A different pattern of results was obtained for character size, depending on whether the display indicators were analog or digital. For analog dials, character size had no systematic effect on performance. However, for digital dials, character size produced an interaction in that the fastest and most accurate performance of all conditions was associated with the spatial format consisting of large characters and small spatial separation. In other words, under conditions associated with high legibility and relatively low visual search, more traditional spatial formats exceeded performance levels associated with the RAPCOM format. These findings are relevant for designers when trying to evaluate the relative merits inherent in spatial versus temporal display formats.