An unbiased errors-in-variables approach to detecting unconscious cognition

Greenwald, Klinger and Schuh (1995) have proposed a regression approach for detecting unconscious cognition. An errors-in-variables approach is presented that corrects for measurement error in the predictor and takes into account that the latent predictor variable is assumed to be non-negative. The new approach requires the same input as the uncorrected regression analysis and provides consistent estimates of regression weights as well as valid statistical tests of their significance. In particular, the method yields a consistent estimate of the regression intercept that provides critical evidence for unconscious cognition. A simulation study illustrates these aspects of the new technique. Several data sets are then reanalysed by means of the new method.

Imaging unconscious semantic priming

Visual words that are masked and presented so briefly that they cannot be seen may nevertheless facilitate the subsequent processing of related words, a phenomenon called masked priming. It has been debated whether masked primes can activate cognitive processes without gaining access to consciousness. Here we use a combination of behavioural and brain-imaging techniques to estimate the depth of processing of masked numerical primes. Our results indicate that masked stimuli have a measurable influence on electrical and haemodynamic measures of brain activity. When subjects engage in an overt semantic comparison task with a clearly visible target numeral, measures of covert motor activity indicate that they also unconsciously apply the task instructions to an unseen masked numeral. A stream of perceptual, semantic and motor processes can therefore occur without awareness.

Baseline salivary cortisol levels and preconscious selective attention for threat. A pilot study

This study was conducted to examine the relationship between baseline salivary cortisol (CORT) levels and selective attention for displays of angry faces. Selective attention was investigated using a pictorial emotional Stroop task, comparing colournaming-speed of angry and neutral faces. The task was assessed in supraliminal (unmasked) and subliminal (masked) conditions to 28 non-clinical subjects (14 male and 14 female). Repeated measures analysis of variance revealed a significant interaction between median split CORT levels (low vs. high) and masked face valence (angry vs. neutral). The latter effect was mainly due to significant facilitation in the high CORT subject-group; these subjects seemed to allocate their attention away from the masked angry face. A relation between baseline CORT levels and fast withdrawal behavior is suggested.

Replicable unconscious semantic priming

In 4 experiments, subjects classified visually presented target words as pleasant-unpleasant words or male-female first names. Prime words were similar (congruent) or dissimilar (incongruent) in meaning to targets. Brief duration of prime words (17, 33, or 50 ms), along with pre- and postmasking, prevented most subjects from perceiving their physical and semantic properties. By constraining response latencies to fall within a response window--a narrow time band that occurred earlier than subjects would ordinarily respond--these experiments consistently produced subliminal priming effects, indicated by greater error rates for incongruent than congruent priming trials. This conclusion was confirmed by analyzing magnitude of priming as a regression function of prime perceptibility using the method of A. G. Greenwald, M. R. Klinger, and E. S. Schuh (1995). The data of each experiment passed their significant-intercept criterion for demonstrating unconscious cognition.

Distinguishing unconscious from conscious cognition--reasonable assumptions and replicable findings: reply to Merikle and Reingold (1998) and Dosher (1998)

S. C. Draine and A. G. Greenwald (1998) demonstrated replicable unconscious semantic priming by combining a response window procedure, which increases priming effects by requiring rapid responding, and a regression analysis in which the regression intercept is a marker for unconscious cognition. The commentaries by B. A. Dosher (1998) and by P. M. Merikle and E. M. Reingold (1998) raise two questions about conclusions based on these methods: (a) Did Draine and Greenwald (1998) demonstrate an indirect effect (subliminal priming) in the absence of a direct effect (i.e., visibility of the subliminal priming words)? and (b) Did Draine and Greenwald (1998) demonstrate dissociation of conscious from unconscious cognition? The first question has reassuring responses that are reviewed here. The second question is answered by pointing out that although Draine and Greenwald (1998) did not claim to have established such dissociation, they provided data that advance the plausibility of that conclusion.

Time course of corticospinal excitability in reaction time and self-paced movements

We used transcranial magnetic stimulation (TMS) to study the time course of corticospinal excitability before and after brisk thumb abduction movements, either in a simple reaction time (RT) paradigm or self-paced. Premovement increase in corticospinal excitability began about 20 msec earlier for self-paced compared with simple RT movements. For both simple RT and self-paced movements after electromyographic (EMG) offset, there was a first period of increased excitability from 0 to 100 msec, followed by a second period from 100 to 160 msec. Corticospinal excitability was decreased from about 500 to 1,000 msec after EMG offset for both types of movements. Our results show that motor preparation that begins 1.5 to 2 seconds before self-paced movement is not associated with increased corticospinal excitability. The first phase of increased corticospinal excitability after EMG offset may be due to activity of motor cortex neuron subthreshold for activating spinal motor neurons, and the second phase may reflect a subthreshold second agonist burst. The period of decreased corticospinal excitability after movement corresponds to the onset of event-related synchronization (ERS) of electroencephalographic signals in the 20-Hz band, and supports the hypothesis that ERS may be related to an inactive, idling state of the motor cortex.

On demonstrating unconscious perception: comment on Draine and Greenwald (1998)

S. C. Draine and A. G. Greenwald (1998) have described a methodology based on regression analysis for demonstrating unconscious perception. They have suggested that their methodology represents a major improvement over existing methodologies. An analysis of their methodology reveals that it is closely related to the classic dissociation paradigm. As such, interpretation of their results is compromised by the same issues concerning the measurement of awareness that have plagued all previous attempts to use the dissociation paradigm to demonstrate unconscious perception in the complete absence of conscious perception.

Correcting for measurement error in detecting unconscious cognition: comment on Draine and Greenwald (1998)

A. G. Greenwald, M. R. Klinger, and E. S. Schuh (1995) have proposed a regression method for detecting unconscious cognition in experiments that obtain measures of indirect and direct effects of stimuli with suspected unconscious effects. Their indirect-on-direct-measure regression approach can produce misleading evidence for indirect effects in the absence of direct effects when the direct-effect measure has typical measurement error. This article describes an errors-in-variables variant of the regression method that corrects for error in the direct-effect measure. Applied to the uses of the regression method by S. C. Draine and A. G. Greenwald (1998) in this issue, the errors-in-variables method affirms substantial evidence for indirect effects in the absence of direct effects.

Reply to Greenberg's critique of Malik, et al.'s experiment on the method of subliminal psychodynamic activation

Greenberg raised two issues concerning an experiment reported by Malik, et al. on the method of subliminal psychodynamic activation. One relates to the appropriateness of control and threshold stimuli and the other to the use of subjective thresholds. Both concerns are addressed.

Effect of subthreshold target stimuli on event-related potentials

OBJECTIVES

Event-related potentials (ERPs) elicited by subthreshold visual stimuli were studied to assess the relationship between unconscious cognitive processing and the electrical activity of the brain.

METHODS

A new method of modified visual oddball paradigm with supraliminal and subliminal stimuli was applied. Prior to the experiment, the individual 'subjective' threshold for the conscious discrimination between frequent and target stimuli was established for each subject. Supraliminal and subliminal, frequent and target visual stimuli were then alternatively presented in random order to each subject.

RESULTS

Both the individual and the grand average ERPs revealed a typical response (P3) in the parietal region after supraliminally presented target stimuli. In subliminal conditions an analogous positive deflection in the central-parietal region was observed, which was elicited by the target stimulus, but not the frequent stimulus. Its latency could be clearly distinguished from the latency of the classical P3, the time difference between the two waveforms was approximately 100 ms.

RESULTS

The results of this study revealed the impact of unconscious processing to target stimuli on the configuration of event-related responses.

Neural response during preference and memory judgments for subliminally presented stimuli: a functional neuroimaging study

Preexposing subjects to visual stimuli is sufficient to establish a subsequent preference, even when previous exposure is subliminal, such that explicit recognition is at chance. This influence of previous exposure on preference judgments, known as the "mere exposure effect," is a form of unconscious memory. The present functional neuroimaging study examines the mechanism of this effect. Nine volunteer subjects were studied using functional imaging while making forced choice judgments about abstract stimuli on the basis of either preference or memory. Each judgment type was made under two conditions: under one condition one or the other stimulus had previously been presented subliminally, whereas under the second condition both stimuli were novel. Memory judgments were associated with activation of left frontopolar cortex and parietal areas, whereas preference judgments were associated with activation of medial prefrontal cortex and regions of occipital cortex. The modulation of preference by objective familiarity (implicit memory) was associated with right lateral frontal activation. Significant activation of hippocampal gyrus was seen in response to objective stimulus novelty, regardless of judgment type required. Our data thus demonstrate activations of a memory system independent of recollective experience. Dissociable activations within this system implicate a frontopolar involvement in explicit retrieval attempt and right lateral prefrontal cortex involvement in implicit memory expressed in preference judgments. Furthermore, the results suggest that hippocampal response to stimulus novelty can be independent of conscious reportability of familiarity.

[Delusions and intuition]

Taking into account the different concepts of delusion and analysing rational and intuitive cognition, the present phenomenological-conceptual study aims at defining the essential nature of delusion. Intuitive cognition as a result of holistic processing is founded in the development of polysensoric-kinaesthetic basic pictures (eidetic matrices), which are recognized preverbally and prereflexively by subliminal perception of corresponding eidetic structures. A positive match between a matrix and a given phenomenon produces an eidetic feeling. This eidetic feeling encompasses three aspects. The first is a preverbal knowledge of something as something definite. As a direct self-reference, the second is the feeling of an object-inherent significance of the given phenomenon for the subject itself. Thirdly, a power vector is perceived to derive from the object. The application of this concept allows us to consider delusion as a disturbance in the system of holistic information processing. This disturbance is characterized by a disinhibition and actualization of eidetic matrices in different ways. The resulting eidetic feeling we call delusion; its expression in thoughts and words we call a delusional idea. All features of an eidetic feeling can be demonstrated in delusion. Owing to their special intensity and suspended reason, they mostly appear to be unique. The analysis of the eidetic structures of delusion allows a deeper understanding of delusion and facilitates both its diagnosis and its differentiation. Heterogeneous terms, such as delusional mood, idea of meaning, idea of reference, delusional notion and delusional perception emerge in an understandable context.

[Temporal illusory conjunction in RSVP tasks: effects of target complexity]

We examined the complexity effects of stimuli and tasks on temporal illusory conjunction in the Rapid Serial Visual Presentation (RSVP) tasks. Subjects were asked to report the partially defined target. We found that error patterns greatly depended on the visual complexity of stimuli. In the case of visually complex stimuli such as Kanji characters consisting of many strokes, pre-target intrusion errors were dominant. In contrast, post-target intrusion errors mainly occurred for visually simple stimuli such as alphabetic letters. Moreover, when target letters were not defined by a specific feature, pre-target intrusion errors were dominant for alphabetic letters. These results were discussed in view of the limited capacity of visual attention.

How limited is the unconscious? A brief commentary

This report discusses the problems associated with the prevailing view that the province of unconscious influence is highly restricted. It is argued that present empirical data neither strongly support nor argue against a circumscribed notion of the unconscious.

Alterations of motor cortical inhibition in patients with dystonia

Cortical inhibitory mechanisms were investigated with the technique of paired transcranial magnetic stimulation in 10 patients with dystonia of the right arm: six patients had focal, task-specific dystonia (writer's cramp) and three had segmental and one had generalized dystonia. Paired stimuli were delivered in a conditioning-test design during slight voluntary activation of the target muscle, with subthreshold conditioning stimuli at short intervals (3-20 ms) and suprathreshold conditioning stimuli at long intervals (100-250 ms). The amount of inhibition at short interstimulus intervals did not differ significantly between patients and normal subjects. With long interstimulus intervals, patients showed more inhibition of the test response, which was significant at the 150-ms interval. The cortical silent period following a single suprathreshold magnetic stimulus was slightly shorter in patients. No significant difference was detected between the affected side and the unaffected side in patients with unilateral task-specific dystonia, neither in the duration of the silent period nor in the response to paired magnetic stimuli. These results indicate that the different types of motor cortical inhibition are produced by different inhibitory circuits. We propose that the alterations observed in patients with dystonia are the result of impaired feedback from the basal ganglia to motor cortical areas, with the ultimate effect of a flattening of the excitability curve of the cortical motoneuron pool during voluntary muscle activation.

Failure to uncover the effects of unconscious symbiotic fantasies on heart rate and fine motor performance

18 men and 18 women were tachistoscopically shown the stimuli MOMMY AND I ARE ONE, DADDY AND I ARE ONE, and MYMMO NAD I REA ENO, at subjective thresholds (subliminal condition) and at 500 msec. (supraliminal condition). Following exposure to each stimulus, subjects performed a fine motor line-tracing task. Heart rate was monitored continuously during stimulus presentation and the fine motor task. Analysis showed subjects did not respond more positively with decreased heart rate or fewer errors on the fine motor task following the MOMMY message than the anagram phrase, thereby providing no support for the hypotheses. No correlation was found between responsiveness to the MOMMY message and scores on measures of self-perception and kinship. In the light of mounting negative evidence, the validity of the method of subliminal psychodynamic activation is questioned.

[The effects of subliminal and supraliminal presentation of trait-related words on person perception]

The present experiment was conducted to investigate how prior information affects subsequent person perception and when perceivers can control such an effect. One of three types of trait related words (i.e., hostility-related, friendliness-related, and neutral words) was subliminally or supraliminally presented to subjects, and subsequently, subjects rated the impression of four targets: a hostile person, a friendly person, a neutral person and themselves. Although results did not show that supraliminally presented words affected targets' impressions, they showed that the impressions sometimes varied with the valence of subliminally presented words regardless of targets' valence. The mechanism and controllability of priming effects in person perception were discussed.

The effects of subliminal symbiotic stimulation on free-response and self-report mood

Research has shown that subliminal presentation of MOMMY AND I ARE ONE (MIO) can help improve adaptive functioning. Two experiments tried to determine whether changes in mood, especially free-response mood, could help explain these findings. In one experiment, 20 men were randomly assigned to receive either a subliminal MIO or control stimulus. Results showed predicted effects on a free-response and no effects on a self-report mood measure. In the other experiment, 54 male subjects randomly received one of three subliminal stimuli. They evidenced the same pattern of mood results. Sentential semantics were shown to be relevant to the obtained results. Ascending threshold and 150 forced-choice discrimination trials demonstrated that subjects could not report stimulus content. It was concluded that MIO effects were attributable to unconscious processing of the entire message and that free-response mood may partly mediate these effects. Suggestions for future research were offered.

Disclosure of contextually hidden sexual images embedded in an advertisement

The discovery of sexual images embedded in an advertisement significantly affected responses to the advertisement by 147 female and 159 male undergraduates.

Stroop and mood/memory measures in the study of unconscious "oneness"

Adaptive behavior following subliminal stimulation with "Mommy and I are One" (MIO) is a poorly understood finding. Positive mood may explain adaptive behavior, but we replicated an earlier finding that effects can also include negative mood. Color naming in a Stroop paradigm was slower on "symbiosis" words (Cohen's d = .19 to .56). Perhaps a "oneness" structure if primed has different affective correlates in different participants.

Alexithymia in patients with eating disorders: an investigation using a new projective technique

The concept of alexithymia was scrutinized in a group of female patients with eating disorders: 15 anorectics and 13 bulimics (mean age of 27 yr.), plus a control group of 21 (mean age 38 yr.). Subjects were interviewed and tested. In the main test an ambiguous face was flashed briefly on a screen opposite the viewer who had to describe her impressions. To enhance the ego-involvement, subliminal words (I, I ILL, I WELL) were presented before each exposure. Contrary to expectations the present patients used more emotional words than controls. Instead, they employed alternative strategies to avoid empathizing. The results were interpreted as indicating a pronounced incapacity for emotional understanding.

Effects of nondirective suggestions on pain tolerance, pain threshold and pain intensity perception

In this experiment, we followed the issue whether nondirective suggestions have an effect on pain threshold, pain tolerance, and perception of pain intensity. 48 healthy subjects consented to take part. At intake into the study (t1), pain threshold and pain tolerance were assessed in all subjects using a pressure algometer. Perception of maximum pain intensity perception was rated on a scale of 0 to 25. Seven days later, the session was repeated (t2). Subjects were randomly assigned to one of two groups. One group received nondirective suggestions as pretreatment. Subjects listened to a tape of 20 min. which consisted of general information about pain theory. In this context, suggestions for coping with pain were placed. The other group served as a control and received no pretreatment. Analysis showed that pain tolerance was significantly prolonged in the group who received nondirective suggestions, while pain threshold and perception of maximum pain intensity did not differ across groups. This study demonstrates that nondirective suggestions are effective in prolonging pain tolerance. It can be stated that, beside information, cues on coping with pain may be helpful in clinical practice.