One version of direct response priming requires automatization of the relevant associations but not awareness of the prime

Do You Control Your Unconscious Action Impulses?

A crucial aspect of self-control is the voluntary inhibition of impulsive actions. Stimuli can elicit impulses (or preparation) to act not only in the presence but also in the absence of perceptual awareness, but whether people control action impulses elicited by unconscious stimuli remains unclear. This study used a masked prime version of the Go/NoGo/Free task and combined mathematical modeling of behavioral data to investigate whether people control the unconscious action impulses. In the experiment, when the subliminal prime stimulus triggers the unconscious action impulse, participants need to freely decide whether or not to perform the action. The results showed that the no-response rate was higher in Go-prime free-choice trials than in NoGo-prime free-choice trials, and there were marginally larger negative drift rates in the former than in the latter. The results suggest that people are more likely to make inhibitory decisions about unconscious action impulses. This finding provides support for a framework that extends the feedback loop model of intentional inhibition.

Two fundamentally different mechanisms by which unconscious information impairs behavioral performance: Evidence from fMRI and computational modeling

It is increasingly clear that unconscious information impairs the performance of the corresponding action when the instruction to act is delayed. However, whether this impairment occurs at the response level or at the perceptual level remains controversial. This study used fMRI and a computational model with a pre-post design to address this elusive issue. The fMRI results showed that when the unconscious information containing strong stimulus-response associations was irrelevant to subsequent stimuli, the precuneus in the parietal lobe, which is thought to be involved in sensorimotor processing, was activated. In contrast, when the unconscious information was relevant to subsequent stimuli, regardless of the strength of the stimulus-response associations, some regions in the occipital and temporal cortices, which are thought to be involved in visual perceptual processing, were activated. In addition, the percent signal change in the regions of interest associated with motor inhibition was modulated by compatibility in the irrelevant but not in the relevant stimuli conditions. Modeling of behavioral data further supported that the irrelevant and relevant stimuli conditions involved fundamentally different mechanisms. Our finding reconciles the debate about the mechanism by which unconscious information impairs action performance and has important implications for understanding of unconscious cognition.

Influences of Music Reading on Auditory Chord Discrimination: A Novel Test Bed for Nonconscious Processing of Irrelevant Prime Meaning

The question whether nonconscious processing could involve higher-level, semantic representations is of broad interest. Here, we demonstrate semantic processing of task-relevant and task-irrelevant features of nonconscious primes within a novel, empirical test bed. In two experiments, musicians were visually primed with musical note triads varying in mode (i.e., major vs minor) and position (i.e., the arrangement of notes within a triad). The task required to discriminate only the mode in the following auditory target chord. In two experimental blocks, primes were either consciously visible or masked, respectively. Response times for auditory discrimination of the modes (relevant dimension) of heard triads were measured. Crucially, the targets also varied with respect to mode and position, creating different grades of congruency with the visual primes. Based on the Theory of Event Coding, we expected and found interactions between relevant and irrelevant semantic characteristics of masked primes, illustrating that even irrelevant prime meaning was processed. Moreover, our results indicated that both task-relevant and task-irrelevant prime characteristics are processed in nonconscious conditions only, and that practice in ignoring uninformative conscious primes can be transferred to a subsequent block. In conclusion, this study demonstrates cross-modal, automatic semantic processing using a novel approach to study such effects.

Alcohol Hangover Differentially Modulates the Processing of Relevant and Irrelevant Information

Elevated distractibility is one of the major contributors to alcohol hangover-induced behavioral deficits. Yet, the basic mechanisms driving increased distractibility during hangovers are still not very well understood. Aside from impairments in attention and psychomotor functions, changes in stimulus-response bindings may also increase responding to distracting information, as suggested by the theory of event coding (TEC). Yet, this has never been investigated in the context of alcohol hangover. Therefore, we investigated whether alcohol hangover has different effects on target-response bindings and distractor-response bindings using a task that allows to differentiate these two phenomena. A total of n = 35 healthy males aged 19 to 28 were tested once sober and once hungover after being intoxicated in a standardized experimental drinking setting the night before (2.64 gr of alcohol per estimated liter of body water). We found that alcohol hangover reduced distractor-response bindings, while no such impairment was found for target-response bindings, which appeared to be unaffected. Our findings imply that the processing of distracting information is most likely not increased, but in fact decreased by hangover. This suggests that increased distractibility during alcohol hangover is most likely not caused by modulations in distractor-response bindings.

Attentional modulation of unconscious inhibitory visuomotor processes: An EEG study

The present study examined the role of attention in unconscious inhibitory visuomotor processes in three experiments that employed a mixed paradigm including a spatial cueing task and masked prime task. Spatial attention to the prime was manipulated. Specifically, the valid-cue condition (in which the prime obtained more attentional resources) and invalid-cue condition (in which the prime obtained fewer attentional resources) were included. The behavioral results showed that the negative compatibility effect (a behavioral indicator of inhibitory visuomotor processing) in the valid-cue condition was larger than that in the invalid-cue condition. Most importantly, lateralized readiness potential results indicated that the prime-related activation was stronger in the valid-cue condition than in the invalid-cue condition and that the followed inhibition in the compatible trials was also stronger in the valid-cue condition than in the invalid-cue condition. In line with the proposed attentional modulation model, unconscious visuomotor inhibitory processing is modulated by attentional resources.

The internal temporal dynamic of unconscious inhibition related to weak stimulus-response associations

Unconscious inhibition has generally been perceived to be dependent on stimulus-response (S-R) associations. Some research has shown that the inhibition related to strong associations increases with response latency to the target. Although this finding suggests that the inhibitory process may need time to unfold, its exact internal temporal dynamic remains to be elucidated. This study examined the role of spontaneous reaction time (RT) fluctuations on sensorimotor processes using letters (Experiments 1 and 2) and faces (Experiment 3), which are more ubiquitous in our environment and do not contain strong associations as stimuli in fixed and free-choice tasks. The results averaged across trials showed that there was no negative compatibility effect in either fixed or free-choice tasks. However, when trials were classified by their response latency, the results indicated that compatibility effects decreased and became negative with longer RTs in the fixed task. These results suggest that the internal temporal dynamic of unconscious inhibitory mechanisms related to fixed responses remains effective for stimuli that do not contain strong S-R associations.

Alcohol Hangover Increases Conflict Load via Faster Processing of Subliminal Information

The detrimental effects of acute alcohol intoxication and long-term alcohol (ab)use on cognition are well-known. Yet, only little is known about the cognitive effects of an acute alcohol hangover, even though it might affect executive functions associated with workplace performance or driving skills. Given that alcohol hangover may increase the speed of information accumulation, we assessed the behavioral effects of conflict load (induced by a subliminal prime) on cognitive control, as assessed via the Flanker effect. We employed a counter-balanced within-subject design, where n = 25 healthy young males were tested once after a sober night and once after a night of experimentally induced heavy drinking of cheap brandy/red wine (2.6375 g alcohol per estimated liter of body water within 2–3 h). Alcohol hangover neither increased the cognitive conflicts induced by consciously processed distractors alone (i.e., the Flanker effect), nor modulated conflict adaptation (i.e., the Gratton effect). Instead, hangover potentiated the detrimental effects of conflicting subliminal primes on top-down cognitive conflicts. This effect was likely due to an increase in the speed of information accumulation from visual stimuli and the resulting increase in subliminal conflict load induced by incompatible primes. We further found the size of this effect to be positively correlated with age and subjective sleepiness during the hangover state, but the hangover effect remained significant even after correcting for those covariates. We further found no correlation of the behavioral effect with the subjective overall rating of hangover symptoms or the maximal breath alcohol concentration reached during prior intoxication. Taken together, our findings suggest that alcohol hangover may affect cognitive performance due to an increase in non-conscious processing of visual distractors. While the size of this effect might increase with age and sleepiness, it is not entirely dependent on those covariates and not necessarily related to subjective ratings of general hangover symptoms/impairment.

The Influence of Masked Stimuli on Response Selection: Evidence from a Semantic Categorization Task

Unconscious visual stimuli can be processed by human observers and influence their behaviour. A striking example is a phenomenon known as "free-choice priming," where masked "prime" stimuli-of which participants are unaware-modulate which of two response alternatives they are likely to choose. Recent efforts to uncover the mechanisms underlying this intriguing effect have revealed that free-choice priming can emerge even in the absence of automatized stimulus-response (S-R) associations between masked primes and specific motor responses, indicating that free choices can be influenced by a masked prime's meaning (Ocampo, 2015). It remains unknown, however, whether masked primes bias response selections because they are implicitly classified according to task instructions, or because spreading activation occurs within the prime's semantic network. To adjudicate between these two possibilities, participants in the present experiment categorised targets as either animals or people and selected which of two response alternatives they wanted to make following presentation of a free-choice target. Crucially, while implicit classifications could proceed during processing of both animal and person masked primes, only animal primes could trigger spreading activation within their semantic network. This manipulation modulated free-choice priming; only masked animal primes influenced response selections to free-choice targets. This result indicates that an automatic spreading activation mechanism might underlie a masked prime's ability to influence free-choice responses.

Exploring the contributions of the supplementary eye field to subliminal inhibition using double-pulse transcranial magnetic stimulation

It is widely accepted that the supplementary eye fields (SEF) are involved in the control of voluntary eye movements. However, recent evidence suggests that SEF may also be important for unconscious and involuntary motor processes. Indeed, Sumner et al. ([2007]: Neuron 54:697-711) showed that patients with micro-lesions of the SEF demonstrated an absence of subliminal inhibition as evoked by masked-prime stimuli. Here, we used double-pulse transcranial magnetic stimulation (TMS) in healthy volunteers to investigate the role of SEF in subliminal priming. We applied double-pulse TMS at two time windows in a masked-prime task: the first during an early phase, 20-70 ms after the onset of the mask but before target presentation, during which subliminal inhibition is present; and the second during a late phase, 20-70 ms after target onset, during which the saccade is being prepared. We found no effect of TMS with the early time window of stimulation, whereas a reduction in the benefit of an incompatible subliminal prime stimulus was found when SEF TMS was applied at the late time window. These findings suggest that there is a role for SEF related to the effects of subliminal primes on eye movements, but the results do not support a role in inhibiting the primed tendency. Hum Brain Mapp 38:339-351, 2017. © 2016 Wiley Periodicals, Inc.

The rapid-chase theory does not extend to movement execution

It is assumed that the processing of a prime followed by a mask occurs sequentially in a feedforward manner when the three (initiation, takeover, and independence) criteria outlined by the rapid-chase theory are met. The purpose of the current study was to determine if the processing of the prime and mask fit the predictions of the rapid-chase theory when the prime and mask are presented during an ongoing movement. In two experiments, participants made rapid pointing movements to a target indicated by the mask. In Experiment 1, the prime was presented at movement onset and the prime-mask stimulus onset asynchrony (SOA) was manipulated. In Experiment 2, the prime-mask SOA was constant but the delay between movement and prime onset was manipulated. Although the results support the initiation and takeover criteria, the data did not support the independence criterion. Consequently, the rapid-chase theory does not appear to extend to movement execution.