Research Article: Top-down contingent feature-specific orienting with and without awareness of the visual input

Date Published: December 22, 2011

Publisher: University of Finance and Management in Warsaw

Author(s): Ulrich Ansorge, Gernot Horstmann, Ingrid Scharlau.

http://doi.org/10.2478/v10053-008-0087-z

Abstract

In the present article, the role of endogenous feature-specific orienting for
conscious and unconscious vision is reviewed. We start with an overview of
orienting. We proceed with a review of masking research, and the definition of
the criteria of experimental protocols that demonstrate endogenous and exogenous
orienting, respectively. Against this background of criteria, we assess studies
of unconscious orienting and come to the conclusion that so far studies of
unconscious orienting demonstrated endogenous feature-specific orienting. The
review closes with a discussion of the role of unconscious orienting in action
control.

Partial Text

Active vision – orienting towards visual stimulation – has evolved
over hundreds of millions of years. Even organisms as simple as nematodes or
protozoa show phototaxis, that is, they move towards light sources. How is orienting
brought about? Is awareness of the visual input (i.e., conscious
vision) necessary for it? We do not know whether simple organisms, such
as Nematodes, have faint precursors of awareness. Given that their nervous systems
are not very complex, they probably orient without awareness and conscious vision.
However, to date, only introspective report taps into awareness, and we do not know
how to assess awareness objectively so that we can tweak it in animals. Fortunately,
the hypothesis of unconscious visual orienting can also be tested with humans. There
are now numerous articles demonstrating orienting of attention without awareness
(cf. McCormick, 1997; Scharlau, 2007). For example, McCormick (1997) presented his participants with the target of a reaction
time task either to the left or to the right of the screen center. Participants did
not know at which position the target was shown. Prior to the target, a brief cue
appeared at one of the two possible target positions. As a consequence of the
participants’ covertly orienting towards the cues, target responses were
facilitated when cue and target appeared in the same position rather than in
different positions. This was the case even though the participants remained
un-aware of the cue due to a low cue-background contrast.

A vast amount of research suggests that one major function of orienting is the
facilitation of perception of visual information at the selected position (e.g.,
Posner, 1980; Titchener, 1908; Treisman
& Gelade, 1980). In the typical experiment, one of several relevant
visual target stimuli is presented at one of several spatial positions. Participants
neither know at which position the next target will be shown, nor do they know the
target’s exact identity. In this situation, prior orienting of the
participants towards one of the potential target positions improves the
participants’ accuracy of discriminating a target at this location and their
speed of responding to it (e.g., Jonides,
1981; Müller & Rabbitt,
1989; Yantis, 1988, 1993; Yantis
& Jonides, 1984). For instance, target discrimination is better when
a small cue is presented shortly before target onset and at the same position (SP)
as the target than when the cue indicates a different position (DP) than the target
(e.g., Jonides, 1981).

Going one step further, the strongest arguments for a temporal pre-cedence of feature
selection over orienting came from studies showing that orienting is even
conditional on prior feature selection. A test of this sequence requires fulfillment
of three conditions, as these were paradigmatically defined in so-called contingent
capture experiments (Folk, Remington, &
Johnston, 1992). Contingent capture of attention denotes
a form of orienting that is conditional on a match between top-down controlled
templates for relevant visual features and actually selected visual features of an
input stimulus. According to this concept, only stimuli with a feature matching to
the search template elicit orienting towards their position. It is clear that the
very concept of contingent capture requires that features, such as color or shape of
a stimulus, can be selected prior to orienting towards this stimulus.

How does orienting operate in the case of unconscious visual stimuli? Basically, the
two options discussed above have also been studied with unconscious visual stimuli:
exogenous orienting preceding feature selection on the one hand, and endogenous
feature-contingent orienting on the other.

In the present review, we have carefully summarized the general conditions that must
be fulfilled by an experimental protocol for demonstrating endogenous orienting to
visual stimuli, for exogenous orienting, and for orienting to unconscious visual
stimuli. We have shown that there is only one fail-safe criterion by which it can be
concluded with certainty that an orienting effect reflects exogenous orienting: the
absence of a fitting endogenous feature-specific search criterion as a precondition
for an orienting effect (cf. Folk et al.,
1992). We think that some studies that used conscious cues for orienting
successfully pass this criterion and thus support exogenous orienting (e.g., Burnham & Neely, 2008).

 

Source:

http://doi.org/10.2478/v10053-008-0087-z

 

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