Features are mislocalized and “travel” into the focus of
attention. (A) Most subjects claim to focus on one of
the two outside edges of the grating to judge the direction of induced
offset (preferred edge). To test this statement, we displayed a vernier
followed by a grating in three conditions. In the first condition (Pref
1), the vernier is followed by a grating having only straight elements.
Subjects attend to their preferred edge. In the second condition (Pref
2), the grating comprises four elements without offset plus an
additional double-bar carrying an offset with offset direction
opposite to the vernier. This element is located
opposite the subject's preferred edge. Observers attend to their
preferred edge. In the third condition (Non-Pref) the same stimuli were
used as in the condition before (that is, outer element offset in
opposite direction than vernier). However, subjects were instructed to
switch attention to their nonpreferred edge. (B)
Focusing on the preferred location hardly changes the amount of correct
responses determined according to the foregoing vernier
independent of whether (Pref 1) or not (Pref 2) the grating comprised
an element with a real offset. However, focusing on the opposite
location, where the offset element is displayed, leads to a very
significant reduction of correct responses. This indicates that the
offset element of the grating determines decision
(Non-Pref). (C) To investigate feature inheritance in a
more quantitative fashion, the vernier was presented at the five
positions of the grating having five straight elements. Position 1
indicates the preferred location, position 5 the opposite location.
Percentage of correct responses drops monotonically and almost linearly
from its maximum if the vernier is presented close to the preferred,
attended edge to almost chance level at the nonpreferred edge of the
grating. C also shows the dependence of performance on
interstimulus (ISI) time between vernier and grating (for two
observers, 30 ms; for the other one, 20 ms).