An investigation of some factors which impede the acquisition of visually displayed information

Two factors which impede the acquisition of visually displayed information were investigated. These were: (a) optical defocus simulating ametropia, and (b) visual distraction by complex irrelevant displays presented in the periphery. Three separate experiments were carried out. The first two investigated defocus for: (a) the detection of small luminous disc targets exposed briefly against a uniform luminous surround, and (b) the resolution and recognition of alphabetic information presented as single words in 'standard' print styles but at small angular subtense. Defocus was found to degrade both functions of detection and recognition, and a comparison of two analyses of visual performance - frequency of seeing with rate of information transmission - revealed that in addition to increasing the target size for threshold of recognition, defocus slowed the processing of visual information. The third experiment investigated distraction from irrelevant magazine advertisements or photographs. Distraction was effective in degrading tracking performance as well as increasing response times to the peripheral task only when the operator was under severe mental load, or when the physical effects of the distraction stimulus (eg disability glare) were excessive. The experiments were conducted in the context of the road traffic situation but have generality of application to other environments where good visual performance is important. Both factors were found to degrade visual performance significantly, and both have important connotations in the practical situation.

  • Supplemental Notes:
    • Thesis submitted in partial fulfilment of the regulations for admission to the degree of Doctor of Philosophy.
  • Authors:
    • Johnston, A W
  • Publication Date: 1974-2


  • English

Media Info

  • Pagination: 1 vol

Subject/Index Terms

Filing Info

  • Accession Number: 01437746
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ATRI
  • Created Date: Aug 24 2012 9:10PM