Demonstrating perception without visual awareness: Double dissociations between priming and masking

A double dissociation impressively demonstrates that visual perception and visual awareness can be independent of each other and do not have to rely on the same source of information (T. Schmidt & Vorberg, 2006). Traditionally, an indirect measure of stimulus processing and a direct measure of visual awareness are compared (dissociation paradigm or classic dissociation paradigm, Erdelyi, 1986; formally described by Reingold & Merikle, 1988; Merikle & Reingold, 1990; Reingold, 2004). If both measures exhibit opposite time courses, a double dissociation is demonstrated. One tool that is well suited to measure stimulus processing as fast visuomotor response activation is the response priming method (Klotz & Neumann, 1999; Klotz & Wolff, 1995; see also F. Schmidt et al., 2011; Vorberg et al., 2003). Typically, observers perform speeded responses to a target stimulus preceded by a prime stimulus, which can trigger the same motor response by sharing consistent features (e.g., shape) or different responses due to inconsistent features. While consistent features cause speeded motor responses, inconsistent trials can induce response conflicts and result in slowed responses. These response time differences describe the response priming effect (Klotz & Neumann, 1999; Klotz & Wolff, 1995; see also F. Schmidt et al., 2011; Vorberg et al., 2003). The theoretical background of this method forms the Rapid-Chase Theory (T. Schmidt et al., 2006, 2011; see also T. Schmidt, 2014), which assumes that priming is based on neuronal feedforward processing within the visuomotor system. Lamme and Roelfsema (2000; see also Lamme, 2010) claim that this feedforward processing does not generate visual awareness because neuronal feedback and recurrent processes are needed. Fascinatingly, while prime visibility can be manipulated by visual masking techniques (Breitmeyer & Öğmen, 2006), priming effects can still increase over time. Masking effects are used as a direct measure of prime awareness. Based on their time course, type-A and type-B masking functions are distinguished (Breitmeyer & Öğmen, 2006; see also Albrecht & Mattler, 2010, 2012, 2016). Type-A masking is most commonly shown with a typically increasing function over time. In contrast, type-B masking functions are rarely observed, which demonstrate a decreasing or u-shaped time course. This masking type is usually only found under metacontrast backward masking (Breitmeyer & Öğmen, 2006; see also Albrecht & Mattler, 2010, 2012, 2016). While priming effects are expected to increase over time by Rapid-Chase Theory (T. Schmidt et al., 2006, 2011; see also T. Schmidt, 2014), the masking effect can show an opposite trend with a decreasing or u-shaped type-B masking curve, forming a double dissociation. In empirical practice, double dissociations are a rarity, while historically simple dissociations have been the favored data pattern to demonstrate perception without awareness, despite suffering from statistical measurement problems (T. Schmidt & Vorberg, 2006). Motivated by this shortcoming, I aim to demonstrate that a double dissociation is the most powerful and convincing data pattern, which provides evidence that visual perception does not necessarily generate visual awareness, since both processes are based on different neuronal mechanisms. I investigated which experimental conditions allow for a double dissociation between priming and prime awareness. The first set of experiments demonstrated that a double-dissociated pattern between priming and masking can be induced artificially, and that the technique of induced dissociations is of general utility. The second set of experiments used two awareness measures (objective vs. subjective) and a response priming task in various combinations, resulting in different task settings (single-, dual-, triple tasks). The experiments revealed that some task types constitute an unfavorable experimental environment that can prevent a double dissociation from occurring naturally, especially when a pure feedforward processing of the stimuli seems to be disturbed. The present work provides further important findings. First, stimulus perception and stimulus awareness show a general dissociability in most of the participants, supporting the idea that different neuronal processes are responsible for this kind of data pattern. Second, any direct awareness measure (no matter whether objective or subjective) is highly observer-dependent, requiring the individual analysis at the level of single participants. Third, a deep analysis of priming effects at the micro level (e.g., checking for fast errors) can provide further insights regarding information processing of different visual stimuli (e.g., shape vs. color) and under changing experimental conditions (e.g. single- vs. triple tasks)

A Theory of Visibility Measures in the Dissociation Paradigm

Research on perception without awareness primarily relies on the dissociation paradigm, which compares a measure of awareness of a critical stimulus (direct measures) with a measure indicating that the stimulus has been processed at all (indirect measure). We argue that dissociations between direct and indirect measures can only be demonstrated with respect to the critical stimulus feature that generates the indirect effect, and the observer's awareness of that feature, the critical cue. We expand Kahneman's (1968) concept of criterion content to comprise the set of all cues than an observer actually uses to perform the direct task. Different direct measures can then be compared by studying the overlap of their criterion contents and their containment of the critical cue. Because objective and subjective measures may integrate different sets of cues, one measure generally cannot replace the other without sacrificing important information. Using a simple mathematical formalization, we redefine and clarify the concepts of validity, exclusiveness, and exhaustiveness in the dissociation paradigm, show how dissociations among different awareness measures falsify simple theories of consciousness, and formulate the demand that theories of visual awareness should be sufficiently specific to explain dissociations among different facets of awareness.Comment: v1: initial upload. v2: added arXiv identifier. v3: corrected an error in mathematical notation in the "definition (iii)" section. v5: adds reference to the published article. Note that the manuscript responding to this preprint has now been published in Psychonomic Bulletin & Review and should be cited preferentiall

Demonstrating perception without visual awareness: Double dissociations between priming and masking

A double dissociation impressively demonstrates that visual perception and visual awareness can be independent of each other and do not have to rely on the same source of information (T. Schmidt & Vorberg, 2006). Traditionally, an indirect measure of stimulus processing and a direct measure of visual awareness are compared (dissociation paradigm or classic dissociation paradigm, Erdelyi, 1986; formally described by Reingold & Merikle, 1988; Merikle & Reingold, 1990; Reingold, 2004). If both measures exhibit opposite time courses, a double dissociation is demonstrated. One tool that is well suited to measure stimulus processing as fast visuomotor response activation is the response priming method (Klotz & Neumann, 1999; Klotz & Wolff, 1995; see also F. Schmidt et al., 2011; Vorberg et al., 2003). Typically, observers perform speeded responses to a target stimulus preceded by a prime stimulus, which can trigger the same motor response by sharing consistent features (e.g., shape) or different responses due to inconsistent features. While consistent features cause speeded motor responses, inconsistent trials can induce response conflicts and result in slowed responses. These response time differences describe the response priming effect (Klotz & Neumann, 1999; Klotz & Wolff, 1995; see also F. Schmidt et al., 2011; Vorberg et al., 2003). The theoretical background of this method forms the Rapid-Chase Theory (T. Schmidt et al., 2006, 2011; see also T. Schmidt, 2014), which assumes that priming is based on neuronal feedforward processing within the visuomotor system. Lamme and Roelfsema (2000; see also Lamme, 2010) claim that this feedforward processing does not generate visual awareness because neuronal feedback and recurrent processes are needed. Fascinatingly, while prime visibility can be manipulated by visual masking techniques (Breitmeyer & Öğmen, 2006), priming effects can still increase over time. Masking effects are used as a direct measure of prime awareness. Based on their time course, type-A and type-B masking functions are distinguished (Breitmeyer & Öğmen, 2006; see also Albrecht & Mattler, 2010, 2012, 2016). Type-A masking is most commonly shown with a typically increasing function over time. In contrast, type-B masking functions are rarely observed, which demonstrate a decreasing or u-shaped time course. This masking type is usually only found under metacontrast backward masking (Breitmeyer & Öğmen, 2006; see also Albrecht & Mattler, 2010, 2012, 2016). While priming effects are expected to increase over time by Rapid-Chase Theory (T. Schmidt et al., 2006, 2011; see also T. Schmidt, 2014), the masking effect can show an opposite trend with a decreasing or u-shaped type-B masking curve, forming a double dissociation. In empirical practice, double dissociations are a rarity, while historically simple dissociations have been the favored data pattern to demonstrate perception without awareness, despite suffering from statistical measurement problems (T. Schmidt & Vorberg, 2006). Motivated by this shortcoming, I aim to demonstrate that a double dissociation is the most powerful and convincing data pattern, which provides evidence that visual perception does not necessarily generate visual awareness, since both processes are based on different neuronal mechanisms. I investigated which experimental conditions allow for a double dissociation between priming and prime awareness. The first set of experiments demonstrated that a double-dissociated pattern between priming and masking can be induced artificially, and that the technique of induced dissociations is of general utility. The second set of experiments used two awareness measures (objective vs. subjective) and a response priming task in various combinations, resulting in different task settings (single-, dual-, triple tasks). The experiments revealed that some task types constitute an unfavorable experimental environment that can prevent a double dissociation from occurring naturally, especially when a pure feedforward processing of the stimuli seems to be disturbed. The present work provides further important findings. First, stimulus perception and stimulus awareness show a general dissociability in most of the participants, supporting the idea that different neuronal processes are responsible for this kind of data pattern. Second, any direct awareness measure (no matter whether objective or subjective) is highly observer-dependent, requiring the individual analysis at the level of single participants. Third, a deep analysis of priming effects at the micro level (e.g., checking for fast errors) can provide further insights regarding information processing of different visual stimuli (e.g., shape vs. color) and under changing experimental conditions (e.g. single- vs. triple tasks)

We prefer what we fear: A response preference bias mimics attentional capture in spider fear

Haberkamp A, Biafora M, Schmidt T, Weiß K. We prefer what we fear: A response preference bias mimics attentional capture in spider fear. JOURNAL OF ANXIETY DISORDERS. 2018;53:30-38.The extent to which emotionally significant stimuli capture visual attention remains elusive because a preference for reporting or choosing emotionally significant stimuli could mimic attentional capture by these stimuli. We conducted two prior-entry experiments to disentangle whether phobic and fear-relevant stimuli capture attention or merely produce a response bias in spider-fearful participants. Prior entry denotes the effect that attended stimuli are perceived earlier than unattended stimuli as indicated by temporal order judgments. We presented phobic (spiders), fear-relevant (snakes) and neutral stimuli in pairs with varying temporal onset. The participants' task was to indicate which stimulus was presented first (Experiment 1) or second (Experiment 2). In the first experiment, spider-fearful but not control participants indicated that they had perceived spiders as occurring earlier in time, suggesting a prior-entry effect for spiders in this group. But surprisingly, in the second experiment, spider-fearful participants indicated more frequently that they had seen spiders as being presented second. This finding rules out a genuine prior-entry effect and instead suggests a strong preference for the response option associated with the feared animal. This response bias may result from a hypervigilance toward the feared stimulus and contribute to maintaining avoidance behavior in individuals with specific phobias