In One of the Earliest Studies of Visual Attention, Helmholtz

In one of the earliest studies of visual attention, Helmholtz 1894) constructed a screen on which letters were painted at various distances from the center. Following a brief illumination, he found that

A) he could perceive letters located within the focus of his attention better than letters outside, even when his eyes remained at the center of the screen.
B) although he was unable to remember all the letters on the screen, he could be cued to attend to the top, middle, or bottom row by a tone played just before the illumination.
C) he could perceive letters located within the focus of his attention better than letters outside, but only if he moved his eyes to bring the letters to the center of his visual field.
D) he could remember all the letters on the screen, demonstrating that visual iconic memory increases in capacity with attentional focus.