Research Article: The influence of distracter and target features on distracter induced blindness

Date Published: February 15, 2012

Publisher: University of Finance and Management in Warsaw

Author(s): Lars Michael, Markus Kiefer, Michael Niedeggen.

http://doi.org/10.2478/v10053-008-0103-3

Abstract

The inhibitory effect of the processing of target-like distracters has already
been shown to affect the conscious detection of simple motion and simple
orientation stimuli in a random dot kinematogram. In two experiments we examined
the effects of single-feature motion distracters, single-feature orientation
distracters, and combined-feature distracters containing both motion and
orientation information. The target was specified as a coherent motion episode
(Experiment 1) or as a combined-feature episode where the coherent motion was
accompanied by an abrupt change in line orientation (Experiment 2). Results
showed that (a) the respective feature-specific inhibitory processes operate
separately even when the distracter features are presented simultaneously and
(b) both inhibitory processes contribute to the blindness effect when the
conjunction of two features is defined as the target. Again, this
inhibitory-process is feature-specific: Only features that are defined in the
task are represented in the inhibitory task set. In case of combined- feature
task-sets, these representations remain separate, so that combined-feature
distracters as well as single-feature distracters are able to induce blindness
effects.

Partial Text

The conscious perception of basic visual features depends on the attentional
resources available to the system (Rees, Frith,
& Lavie, 2001). In a series of experiments, we previously
demonstrated that access and processing of relevant information is not only affected
by the presentation of rivaling information, but also by distracters preceding the
target stimulus (Michael, Hesselmann, Kiefer, &
Niedeggen, 2011; Sahraie, Milders, &
Niedeggen, 2001). In our paradigm, two spatially separate rapid serial
visual presentation (RSVP) sequences are shown. In a local stream, the color of a
central fixation point changes at 10 Hz. The surrounding area consists of a random
dot kinematogram (RDK) whose dots follow a random walk. The random global motion is
interrupted by salient events like short episodes of coherent motion for 100 ms. The
subject’s task is to detect the onset of a coherent motion coinciding or
following a red fixation. Thus, the color change in the local stream serves as a cue
to shift attention to the global stream. Task-irrelevant motion episodes or
orientation changes presented prior to the cue serve as distracters and have to be
ignored.

In this experiment, we tested the notion of feature-specific negative attentional
sets and used a simultaneous presentation of coherent motion and orientation changes
as a combined-feature distracter condition in addition to pure motion and pure
orientation distracters (single-feature distracters). If the negative attentional
set that produces the DIB effect is feature-specific and activated endogenously, the
detection of motion targets is expected to be impaired, when distracters contain
motion information whether presented as single-feature motion distracters or as
combined-feature distracters (Hübner et al.,
2003; Michael et al., 2011).

Experiment 1 provided evidence that combined features in the distracter episode have
no different effects on target processing than single-feature distracters. In other
words, the system responds only to the visual features which are defined a priori in
the task set. Therefore, we changed the number of visual features critical for the
task set in our second experiment: Here, the simultaneous presentation of both
features (coherent motion and change in orientation) was defined as the target
whereas the mere presentation of a single feature was to be ignored. As in
Experiment 1, distracter episodes were defined by single-feature events (motion,
orientation) and by combined feature events (motion and orientation).

The inhibitory effect of distracter processing has already been shown to affect the
conscious detection of simple motion stimuli (AMB, attention-induced motion
blindness; Sahraie et al., 2001). Our current
findings extend these results by showing that (a) the respective feature-specific
inhibitory processes operate separately even when the distracter features are
presented simultaneously and (b) both inhibitory processes contribute to the
blindness effect when the conjunction of two features is defined as target. Again,
this inhibitory process is feature-specific.

 

Source:

http://doi.org/10.2478/v10053-008-0103-3

 

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