Experiment 2 was identical to Experiment 1, except that the
boundary boxes were made visible by drawing them in black lines,
as shown in Figure 2.
Observers. Observers were 10 psychology staff members and
10 postgraduate students at Bristol University. Eighteen were naive
to the purpose of the experiment, 10 had previously participated
in Experiment 1, and 16 were nonexperts in participating in visual
psychophysical experiments. All had normal or corrected-to-normal
vision.