Academic journal article Human Factors

Foveal Task Complexity and Visual Funneling

Academic journal article Human Factors

Foveal Task Complexity and Visual Funneling

Article excerpt


Factors such as driving speed and task complexity when using foveal vision are generally regarded as related to the narrowing of the visual field. Although the whole visual field has a width of about 180[degrees], the sensitive area of the retina is only about 2[degrees]. This is physiologically determined by the neural structure of the visual system (retina). Thus eye movement plays an important role in the acquisition of visual information presented in the periphery. People acquire visual information using not only foveal vision but also peripheral vision. The characteristics of peripheral vision in actual behavior are as important as those of foveal vision. The range around a fixation point within which people can recognize or utilize visual information for later recognition is known as the functional visual field. The functional visual field varies from 4[degrees] to 50% depending on many factors. The variation of the functional visual field is very important for cognitive information processing.

The functional visual field is affected by the workload placed on foveal vision, the level of concentration, the familiarity with and context of the peripheral stimulus, and environmental stress. Results of a large number of studies have suggested that information overload in foveal vision induce decrements in peripheral performance (Abernethy & Leibowitz, 1971; Bursill, 1958; Leibowitz & Appelle, 1969; Mackworth, 1965; Provins & Bell, 1970).

Bursill (1958) reported that a decrease in peripheral performance became more pronounced as stimuli moved farther into the periphery. This phenomenon is generally called the funneling effect, a phenomenon in which increasing foveal task complexity causes a narrowed functional visual field. Mackworth (1965) also reported that the more a participant was stressed, the narrower the visual field became and the more funneling occurred. Contrary to these studies, a few studies did not observe a funneling effect but showed that increasing the foveal workload reduced peripheral performance equally at all peripheral locations (Abernethy & Leibowitz, 1971; Leibowitz & Appelle, 1969; Provins & Bell, 1970). Provins and Bell reported that the percentage of missed peripheral signals increased when the participant, using foveal vision, was required to complete the assigned task as quickly as possible. As the activation of foveal vision increased, peripheral performance decreased equally at all peripheral locations as a result of the decrease of the bandwidth of attention. Bartz (1976) reported an exceptional phenomenon, in which performance at the periphery improved as foveal task complexity increased. Different results have been reported on the relationship between foveal task complexity and peripheral performance. Studies on how foveal task complexity affects peripheral performance do not necessarily support a visual funneling effect.

In this study, a method to measure the functional visual field was developed by considering foveal task complexity. Using this experimental paradigm confirmed whether or not a funneling effect would be observed. Some implications for the potential and practical applications of these results in methodology and in design will be given.



Eight healthy male undergraduates, aged 18 to 23 years, participated in the experiment.


The measurement system was prepared on an Engineering Work Station (Sun Ultra60 computer with Solaris 2.6 operating system) with a 19-inch (48-cm) CRT.


The fixation point appeared randomly on the CRT. The fixation point was an outline, and the digits appeared inside it (Figure 1). The luminances of the circle and digits were about 87 cd/[m.sup.2] and 62 cd/[m.sup.2], respectively. The background luminance was 73 cd/[m.sup.2]. The peripheral stimulus was a solid circle. The digits were presented in black. …

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