Effects of age and eccentricity on visual target detection

Abstract

The aim of this study was to examine the effects of aging and target eccentricity on a visual search task comprising 30 images of everyday life projected into a hemisphere, realizing a ±90° visual field. The task performed binocularly allowed participants to freely move their eyes to scan images for an appearing target or distractor stimulus (presented at 10°; 30°, and 50° eccentricity). The distractor stimulus required no response, while the target stimulus required acknowledgment by pressing the response button. One hundred and seventeen healthy subjects (mean age = 49.63 years, SD = 17.40 years, age range 20-78 years) were studied. The results show that target detection performance decreases with age as well as with increasing eccentricity, especially for older subjects. Reaction time also increases with age and eccentricity, but in contrast to target detection, there is no interaction between age and eccentricity. Eye movement analysis showed that younger subjects exhibited a passive search strategy while older subjects exhibited an active search strategy probably as a compensation for their reduced peripheral detection performance.

Keywords: aging; functional visual field; target detection; visual exploration behavior; visual search; visual search strategy.

Figure 1

Experimental setup. (A) Hemisphere, forehead- and chin-rest. In (B), the front panel is removed to illustrate the projection of the images into the cupola. The images are generated with a miniature projector positioned in the upper part of the hemisphere and reflected by a spherical mirror in the lower part (Nef et al., 2013).

Figure 2

Visual saliency analysis. (A) Two example images of the functional visual field test (courtesy of Gabriele Schoenemann, Kurt Bouda/pixelio.de). (B) Corresponding saliency maps. (C) Mean saliency map over all 30 images.

Figure 3

Target and distractor positions. (A) Thirty-six targets positions. (B) Twenty distractors positions

Figure 4

Scatterplot of target detection performance depending on age. Each subjects’ performance is shown with circles, linear broken-line regression with colored solid lines, and the 90% confidence interval is shown with dotted lines and the polynomial regression as a solid black line. (A) Performance at ε_H = 10°. (B) Performance at ε_H = 30°. (C) Performance at ε_H = 50°.

Figure 5

Scatterplot of the reaction time depending on age. Each subjects’ performance is shown with circles, linear broken-line regression with colored solid lines, and the 90% confidence interval is shown with dotted lines and the polynomial regression as a solid black line. (A) Reaction time at ε_H = 10°. (B) Reaction time at ε_H = 30°. (C) Reaction time at ε_H = 50°.

Figure 6

Scatterplot of the gaze position during the test depending on age. Each subjects’ performance is shown with circles, linear regression with colored solid lines, and the 90% confidence interval is shown with dotted lines. (A) Gaze position between 0 and 20°. (B) Gaze position between 20 and 40°. (C) Gaze position between 40 and 60°.