The Impact of Eccentricity within Visual Vigilance Displays

Abstract

The Functional Field of View (FFOV) plays a crucial role in processing task-relevant visual information, especially in activities like driving and operational domains such as aviation and surveillance. Many tasks requiring a wide FFOV also demand sustained attention over prolonged periods. However, performance in vigilance tasks often declines over time (i.e., vigilance decrement). Understanding the interaction between FFOV and vigilance is vital to optimize performance and reduce risks in such settings. Previous studies suggested that attentional availability limits FFOV, as such introducing attention-demanding tasks like vigilance were expected to decrease FFOV over time. Results revealed that response times for the most centrally located stimuli, while faster than more peripheral regions, selectively worsened over time. These results may suggest a strategic trade-off in attention allocation; in order to compensate for reduced availability of attentional resources, relatively difficult, peripheral locations may have been prioritized.

Introduction

Functional field of view (FFOV) is the area around an individual’s visual fixation that can be successfully processed for task-relevant information (Crundall et al., 1999). FFOV facilitates the processing of visual information in both operational and day-to-day settings. We can observe its application in daily tasks such as driving, which require individuals to have the ability to detect and respond to objects or events in their visual field, often in a timely manner (Seya et al., 2013). In driving scenarios, a wide functional field of view enables drivers to anticipate potential hazards in the periphery, such as pedestrians crossing the street or vehicles merging into their lane, thereby facilitating timely responses to ensure safety on the road. Generally, a wide FFOV facilitates superior performance in operational settings where task-critical information is presented in the visual periphery (e.g., aviation, surveillance; Ellis et al., 2002).

Many settings that benefit from a wide FFOV also require vigilance or sustained attention over an extended duration (Roge et al., 2002; Seya et al., 2013). In high-stakes situations like driving or military surveillance, maintaining vigilance is important to ensure readiness to respond to sudden changes or emerging threats (Warm et al., 2015). Additionally, performance often deteriorates as a function of time within these domains, a phenomenon known as the vigilance decrement. To optimize performance outcomes and mitigate risks in domains that require wide FFOV and vigilance, it is crucial to understand how FFOV and vigilance might interact.

Research on FFOV suggests that FFOV is limited by the availability of attention. The introduction of additional attentional demands (e.g., a secondary task) reduces FFOV, meaning that the ability to detect and respond to relatively peripheral stimuli is reduced as the availability of attentional resources is diminished by additional task demands (Williams, 1982). For this study, we expected FFOV to diminish throughout the duration of a vigilance task, aligning with vigilance theories that propose a decline in attentional resource availability as a function of time (Warm et al., 2015).

Approach

Twenty-three participants (5 men, 18 women; M_age = 18.91, SD_age = 0.9) completed a 40-minute vigilance task divided into four, 10-min blocks. Participants fixed their gaze on the center of the display and were then responsible for detecting a critical signal (square) that would sometimes be presented onscreen among distractors (triangles). With each new display, 24 stimuli were presented around the fixation cross at three different levels of eccentricity: 8 stimuli were presented 5 degrees of visual angle from center, 8 stimuli were presented 10 degrees from center, and 8 stimuli were presented at 15 degrees from center. The critical signal could appear in any location and was equally probable at all three eccentricities. A single critical signal appeared among 23 distractors in 8% of displays, and all other displays (92%) contained only 24 distractors. Participants were instructed to respond when a critical signal appeared and to withhold responses when no critical signal was present.

Findings

This study assessed performance in terms of the rate of correct detections and median response time using two separate 3(Eccentricity) × 4(Block) repeated measures ANOVA. Analysis of response times indicated that the eccentricity affected average response time, F(2, 44) = 27.83, p < .001, η_P² = .559. Specifically, signal detection was fastest when the critical signal appeared at the innermost eccentricity (5°) and slowest when it appeared at the outermost, most peripheral eccentricity (15°). This effect replicates previous research on FFOV showing an advantage for the processing of relatively central visual information, compared to relatively peripheral information. However, analysis of the present data also indicated that the superiority of central visual areas was reduced over time, F(6, 132) = 2.43, p < .05, η_P² = .100. This interaction between eccentricity and block variables indicated that response times slowed over time primarily in the innermost eccentricity (5°), but response times were relatively stable in the other, more peripheral eccentricities (10° and 15°).

Analysis of correct detections indicated that the detection rate declined over the vigilance task’s four blocks, F(3, 66) = 3.222, p < .05, η_P² = .128. Unlike response time data, this time-related decrement in correct detections was not significantly influenced by eccentricity. However, examination of sample means revealed a pattern suggestive of that interaction, meaning that the detection rate fell most precipitously in the inner (5°) eccentricity, and less so in the relatively peripheral eccentricities.

Takeaways

The current study indicated—as others have—that relatively central stimuli are more likely to be processed successfully and efficiently than relatively peripheral. However, the current study showed that this advantage can be reduced by prolonged demands for vigilance. Consequently, display designers should consider the possibility that detection performance may decline more severely over time for relatively central stimuli, when the display also demands attention towards relatively peripheral stimuli. We suggest designing with the vigilance decrement in mind if the application requires prolonged monitoring.

From a theoretical perspective, the current results were somewhat surprising. We expected the demands of vigilance to lead to attentional tunneling, which would have been reflected by more severe performance decrements in the relatively peripheral parts of the display compared to the relatively central areas (Mackworth, 1965). Results indicated the opposite pattern (i.e., performance fell most severely in central areas). Theoretical explanations for the vigilance decrement argue that attentional resources are decreasingly available for detection as the task progresses, either because attentional resources are disengaged or depleted (Warm et al., 2015). The observed results suggest that relatively central locations may suffer the most from that decline in attentional resource availability. This effect might be driven by a tradeoff strategy to compensate for reduced availability of attentional resources (e.g., prioritize attending to relatively difficult to detect peripheral stimuli). Future research will be needed to evaluate this and other possibilities.