Elsevier

Consciousness and Cognition

Volume 17, Issue 3, September 2008, Pages 657-671
Consciousness and Cognition

Limited transfer of subliminal response priming to novel stimulus orientations and identities

https://doi.org/10.1016/j.concog.2007.06.007Get rights and content

Abstract

Recently, priming effects of unconscious stimuli that were never presented as targets have been taken as evidence for the processing of the stimuli’s semantic categories. The present study explored the necessary conditions for a transfer of priming to novel primes. Stimuli were digits and letters which were presented in various viewer-related orientations (upright, horizontal, inverted). The transfer of priming to novel stimulus orientations and identities was remarkably limited: in Experiment 1, in which all conscious targets stood upright, no transfer to unconscious primes in a non-target orientation was found. Experiment 2, in which primes were presented without masks, ruled out the possibility that primes were presented too short to allow congruency effects. In Experiments 3 and 4, in which all targets were presented upside down, priming transferred to upright stimuli with target identities but neither to horizontal stimuli nor to stimuli with novel identities. We suggest that whether a transfer of priming to unpracticed stimuli occurs or not depends on observers’ expectations of specific stimulus exemplars.

Introduction

How do stimuli that people are not aware of gain influence on their behavior? Almost from the first demonstration of the effects of unconscious stimuli, this question has been hotly debated. One such demonstration is the response-congruency effect in subliminal priming experiments: responding is faster to clearly visible targets if these are preceded by unconscious primes that are assigned to the same response (congruent trials), as compared to trials where primes are assigned to another response (incongruent trials).

In subliminal priming experiments, presentation of a prime leads to measurable neuronal activation in cortical motor areas that are related to the response assigned to the prime (Dehaene et al., 1998, Eimer and Schlaghecken, 1998). The mechanism underlying prime-induced motor activation is, however, unclear. Dehaene et al. (1998) concluded that a prime elicits a covert motor response (which facilitates performance in congruent trials and impairs it in incongruent ones) by means of its semantic properties: “Because this motor parameter was determined by whether the prime was larger or smaller than 5, the prime must have been categorized at the semantic level.” (Dehaene et al., 1998, p. 599).

This view has been challenged however. Damian (2001) argued that participants acquire target-response associations during experimental practice trials. When these targets occur as primes some time later, they trigger a covert motor response via a consciously learned and persisting memory trace of stimulus–response episodes without deep semantic processing. This reasoning was corroborated by Abrams and Greenwald (2000) who demonstrated that “robust unconscious semantic priming…requires previous classification of visible targets that contain the fragments later serving as primes.” (Abrams & Greenwald, 2000, p. 118).

Most challenging for accounts that deny semantic processing of subliminal stimuli are demonstrations of priming effects from subliminal stimuli that were never presented as targets (e.g. Naccache & Dehaene, 2001). Since participants never had to respond to these primes, stimulus–response associations could not have been learned.

Experimentally, priming by novel stimuli has been realized threefold: novel primes might (a) have the same identities as practiced targets but a different perceptual format. For example, Dell’Acqua and Grainger (1999) found priming effects from pictures when targets were the names of the depicted concepts. Steiner (2003), however, failed to find priming from number words when all targets were Arabic numerals (see also Kunde, Kiesel, & Hoffmann, 2003, Experiment 4). Novel primes might (b) have different identities than the targets but the same perceptual format. Naccache and Dehaene (2001) presented the digits 1, 4, 6, and 9 as targets in a numerical judgment task (smaller vs. larger than 5). The digits 2, 3, 7, and 8 led to congruency effects although not being part of the target set. However, when words denoting small or large objects were categorized regarding object size, only those object names activated responses subliminally which had been presented as targets (Damian, 2001). Novel primes might (c) have different identities and a different perceptual format. For example, Klauer, Eder, Greenwald, and Abrams (2007) found congruency effects of positive and negative adjectives in a valence classification task with smiley faces and grumpy faces as targets. Yet, the number words two, three, seven, and eight did not elicit congruency effects in a numerical quantity judgment task that had to be performed on the digits 1, 4, 6, and 9 (Kunde et al., 2003). Taken together, a transfer of priming to novel unseen stimuli seems to occur under specific conditions but it is far from being a robust phenomenon.

Greenwald, Abrams, Naccache, and Dehaene (2003) reconcile the inconsistent evidence by assuming that primes in principle can activate both long-term semantic memory codes and short-term memory codes established within the experimental context but that “across all relevant studies, contextual memory effects on masked priming have tended to dominate those based on long-term memory” (Greenwald et al., 2003, p. 245). Kunde et al. (2003) propose a similar account differing from that of Greenwald et al. (2003) mainly with respect to the temporal order of these processes. Kunde et al. (2003) suggest that long-term semantic codes primarily operate prior to task performance, namely during task instructions and initial practice trials, to segment internal representations of potential stimulus events into appropriate and inappropriate response conditions (“action-triggers”). Subsequently unconscious primes are processed only up to a level that allows detection of the stimulus’ perceptual match or mismatch with an action trigger. As a consequence, priming occurs for all stimuli that are expected regarding both identity and perceptual appearance (see also Kiesel, Kunde, & Hoffmann, in press).

The aim of the current study was to further elaborate on the transfer of subliminal response priming to novel stimuli. We aimed at finding conditions in which priming by novel stimuli emerges robustly. When scanning available evidence, two conditions seem to be especially suitable to demonstrate transfer of priming to novel stimuli: first, novel primes contain fragments of consciously experienced targets (Abrams and Greenwald, 2000, Greenwald et al., 2003). Second, all experimental stimuli are numbers (Kunde et al., 2003, Naccache and Dehaene, 2001). Numbers appear particularly suitable, because semantic access to number meaning is especially fast, and automatic activation of number meanings has been found even in tasks for which number meaning was irrelevant (Brysbaert, 1995, Dehaene and Akhavein, 1995, Dehaene et al., 1993, Fias et al., 1996).

Experiment 1 of the present study was designed to test whether robust transfer of priming to novel stimuli can be achieved when both of the above conditions are met. Experimental stimuli were numbers, and novelty was achieved by presenting primes in different orientations than targets. Although this orientation change can be considered a relatively moderate format change when compared to previous format manipulations, the transfer of priming failed. Experiment 2 rules out that the lack of priming by novel stimuli in Experiment 1 was due to short presentation and prime-target SOA. In Experiment 3, target orientation was varied compared to Experiments 1 and 2. Targets were now presented upside down instead of upright. As a consequence, priming by masked stimuli did transfer to a subset of perceptually novel stimuli: primes in upright presentation induced priming effects whereas horizontal primes again remained ineffective. Experiment 4 was designed to extend the findings of Experiment 3 to identity-defined novelty. Although the transfer of priming to a novel format was replicated, priming did not transfer to novel stimulus identities. Altogether, the apparently complex pattern of transfer suggests that subliminal stimuli exert priming to the extent to which their identity and physical appearance are expected.

Section snippets

Experiment 1

Participants were to classify numerals as smaller or larger than five. All target digits stood upright. Prime numerals had the same identities as the targets but were presented in different orientations (upright, horizontal, inverted). Compared to other format changes used in the literature, this seems to be a rather moderate modification of prime and target appearance (compare e.g.‘

4’ with ‘FOUR - 4’).

The orientation manipulation establishes conditions under which a transfer of priming

Experiment 2

If it had been shortness of SOA and prime presentation that bar rotated primes from evoking congruency effects in Experiment 1, then congruency effects should be absent even when primes were not masked. We therefore reran Experiment 1 without masks. Priming from unmasked horizontal and inverted stimuli would rule out the objection that their processing takes too long to lead to response-congruency effects with presentation times as short as those used in Experiment 1.

Experiment 3

Participants in Experiment 3 consciously experienced upside down oriented targets while all other experimental conditions remained the same as in Experiment 1. We now expected inverted primes to produce congruency effects as well. First of all this would rule out the possibility that inverted primes cannot cause congruency effects for some principled reason. Second, this manipulation might help to discriminate between two competing accounts of masked priming. If priming was due to acquired

Experiment 4

In Experiment 3, priming transferred—at least temporarily—to stimuli in a novel orientation. Experiment 4 was designed to test whether this transfer extends to primes with novel identities.

The number of digits which can be tilted without remaining physically identical or turning into another digit is limited (e.g. 8 in 0° and 180° are identical, 6 in 0° is identical with 9 in 180° and vice versa). Thus number stimuli do not allow us to create conditions with orientation-defined and

General discussion

Response-congruency effects of subliminal primes have been attributed to either learned stimulus–response associations that become activated when the respective stimulus is presented subliminally, or to unconscious access to the primes’ semantic features. Particularly diagnostic for semantic access is a transfer of subliminal priming to novel prime stimuli that have not been used as targets before, because stimulus–response associations cannot be acquired for such stimuli. Prime novelty can

References (38)

  • U. Ansorge et al.

    Intentions determine the effect of invisible metacontrast-masked primes: Evidence for top-down contingencies in a peripheral cuing task

    Journal of Experimental Psychology: Human Perception and Performance

    (2005)
  • G.E. Bodner et al.

    A retrospective view of masked priming: Toward a unified account of masked and long-term repetition priming

  • M. Brysbaert

    Arabic number reading: On the nature of the numerical scale and the origin of phonological recoding

    Journal of Experimental Psychology: General

    (1995)
  • A.M. Collins et al.

    A spreading-activation theory of semantic processing

    Psychological Review

    (1975)
  • M.C. Corballis et al.

    Decisions about identity and orientation of rotated letters and digits

    Memory & Cognition

    (1978)
  • M.F. Damian

    Congruity effects evoked by subliminally presented primes: Automaticity rather than semantic processing

    Journal of Experimental Psychology: Human Perception and Performance

    (2001)
  • S. Dehaene et al.

    Attention, automaticity, and levels of representation in number processing

    Journal of Experimental Psychology: Learning, Memory, and Cognition

    (1995)
  • S. Dehaene et al.

    The mental representation of parity and numerical magnitude

    Journal of Experimental Psychology: General

    (1993)
  • S. Dehaene et al.

    Imaging unconscious semantic priming

    Nature

    (1998)
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