Thomas Schmidt

• PhD (Dr. rer. nat.), FPsyS
• Professor at RPTU Kaiserslautern-Landau

We present a new experimental technique to induce dissociations between the visibility of a masked prime and its ability to induce a priming effect in response times. In three experiments, we systematically couple an independent variable known to influence the priming effect (prime-mask SOA) with a variable expected to influence prime visibility bu...

Stockart et al. (2024) recommend guidelines for best practices in the field of unconscious cognition. However, they condone the repeatedly criticized technique of excluding trials with high visibility ratings or of participants with high sensitivity for the critical stimulus. Based on standard signal detection theory for discrimination judgments, w...

Research on perception without awareness primarily relies on the dissociation paradigm, which compares a measure of awareness of a critical stimulus (direct measure) 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...

Dissociation paradigms examine dissociations between indirect measures of prime processing and direct measures of prime awareness. It is debated whether direct measures should be objective or subjective, and whether these measures should be obtained on the same or separate trials. In two metacontrast experiments, we measured prime discrimination, P...

Recent advances in autonomous driving systems raise new questions about how to enhance the communication and takeover control between the system and the driver. Eye tracking technologies have shown their feasibility to recognize whether the driver’s gaze is directed ‘on-road’ or ‘off-road’. However, this binary information alone is not sufficient t...

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 wit...

The Negative Compatibility Effect (NCE) is a reversal in priming effects that can occur when a masked arrow prime is followed by an arrow target at a long stimulus-onset asynchrony (SOA). To test the explanation that the NCE is actually a positive priming effect elicited by mask features associated with the prime-opposed response, we devise masks t...

Research on spatial cueing has shown that uninformative cues often facilitate mean response time (RT) performance in valid- compared to invalid-cueing conditions at short cue-target stimulus-onset-asynchronies (SOAs), and robustly generate a reversed or inhibitory cueing effect at longer SOAs that is widely known as inhibition-of-return (IOR). To s...

We propose that any theory of visual awareness must explain the gradient of different awareness measures over experimental conditions, especially when those measures form double dissociations among each other. Theories meeting this requirement must be specific to the measured facets of awareness, such as motion, contrast, or color. Integrated infor...

Skrzypulec (2021) raises the question whether motor activation by masked color primes is based on the same type of color representation as conscious vision. He postulates that the literature on color processing without awareness makes an implicit assumption that "conscious" and "unconscious" color representations have the same properties, in which...

The hypothesis of grounded procedures of separation predicts accentuated effects in individuals with psychiatric disorders, for example, obsessive-compulsive disorders with washing compulsion. This could provide a vantage point for understanding cognitive processes related to specific disorders. However, fully exploring it requires updated experime...

The visual system has to distinguish between information that is relevant and irrelevant for current behavioral goals. This is especially important in automatized responses. Here, we study how task-irrelevant distractors with task-relevant features gain access to speeded, automatized motor responses in a response-priming paradigm. In two tasks, we...

In this Methods paper, we discuss and illustrate a unifying, principled way to analyze response time data from psychological experiments-and all other types of time-to-event data. We advocate the general application of discrete-time event history analysis (EHA) which is a well-established, intuitive longitudinal approach to statistically describe a...

Research on spatial cueing has shown that uninformative cues often facilitate mean response time (RT) performance in valid- compared to invalid-cueing conditions at short cue-target stimulus-onset-asynchronies (SOAs), and robustly generate a reversed or inhibitory cueing effect at longer SOAs that is widely known as inhibition-of-return (IOR). To s...

In response priming experiments, a participant has to respond as quickly and as accurately as possible to a target stimulus preceded by a prime. The prime and the target can either be mapped to the same response (consistent trial) or to different responses (inconsistent trial). Here, we investigate the effects of two sequential primes (each one eit...

Thanks to the work of Anne Treisman and many others, the visual search paradigm has become one of the most popular paradigms in the study of visual attention. However, statistics like mean correct response time (RT) and percent error do not usually suffice to decide between the different search models that have been developed. Recently, to move bey...

Why do we take so much care to obtain high-resolution RT data when we collapse all the temporal information by calculating a single, mean (correct) RT? More and more research findings show that RT variance is not just noise, and that the mean RT is not more informative than any other time point at which responses occur. Furthermore, the dynamic sys...

A longitudinal analysis of RT and accuracy data in typical backward masking paradigms.

Background and objectives: The fast detection of and response to threatening stimuli is an important task of the human visual and motor systems, and is especially challenging when stimuli are ambiguous. This study investigates the perception, evaluation and fast response to ambiguous natural spider stimuli in spider-fearful and non-anxious partici...

Published RT and accuracy data in 3 visual search tasks are analyzed using discrete-time event history analysis. The results reveal new features of visual search performance, such as (a) individual differences in the presence of a pattern of early errors, (b) a relatively flat hazard function in the right tail of the RT distribution in all tasks, a...

Illustrates how the mean (correct) RT and overall error rate conceal the underlying temporal dynamics in the time-dispersed behavior of observers.

In response priming tasks, speeded responses are performed toward target stimuli preceded by prime stimuli. Responses are slower and error rates are higher when prime and target are assigned to different responses, compared to assignment to the same response, and those priming effects increase with prime-target SOA. Here, we generalize Vorberg et a...

In response priming tasks, speeded responses are performed toward target stimuli preceded by prime stimuli. Responses are slower and error rates are higher when prime and target are assigned to different responses, compared to assignment to the same response, and those priming effects increase with prime-target SOA. Here, we generalize Vorberg et a...

Poster presented at the 50th Autumn meeting of experimental cognitive psychology (HexKoP) 2017 in Günzburg, Ulm, Germany.

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 pro...

STATCHECK is an R algorithm designed to scan papers automatically for inconsistencies between test statistics and their associated p values (Nuijten et al., 2016). The goal of this comment is to point out an important and well-documented flaw in this busily applied algorithm: It cannot handle corrected p values. As a result, statistical tests apply...

Statcheck is an R algorithm designed to scan papers automatically for inconsistencies between test statistics and their associated p values (Nuijten et al., 2016). Due to concerns about its reliability and validity, Nuijten et al. (2017) check the output of the program against the sample of 49 papers manually checked by Wicherts et al. (2011), but...

Inhibitory control such as active selective response inhibition is currently a major topic in cognitive neuroscience. Here we analyze the shape of behavioral RT and accuracy distributions in a visual masked priming paradigm. We employ discrete time hazard functions of response occurrence and conditional accuracy functions to study what causes the n...

Note: glmer will often not converge. Instead you could use glmmPQL from the MASS package, as follows (this example fits a cloglog hazard model; for a ca(t) model apply the logit link): fit1 <- glmmPQL(outcome ~ 1 + BinCent1 + BinCent2 + # main effect of time (reference condition) TrialC + TrialC:BinCent1 + TrialC:BinCent2 + # effect of trial numb...

This file contains the person-trial-bin oriented data set of Experiment 1 in Panis and Schmidt (2016). It is used by: R code for inferential statistics using event history analysis, as can be found in the supplementary materials of Panis and Schmidt (2016). You must rename the file to: "pppdataset_NCE_Exp1_n6.Rdata" and use load("pppdataset_NCE_Exp...

Visuomotor Processing and Perception of Natural Morphed Images in Spider Phobics.

Some studies of unconscious cognition rely on judgments of participants stating that they have “not seen” the critical stimulus (e.g., in a masked-priming experiment). Trials in which participants gave invisibility judgments are then treated as those where the critical stimulus was “subliminal” or “unconscious”, as opposed to trials with higher vis...

Rapid motor responses to visual stimuli can involve both the activation and inhibition of motor responses. Here, we trace the early processing dynamics of response genera- tion, examining whether activation and inhibition events form a strict sequence when elicited by sequential stimuli, as we would expect if motor events are driven by fast, stimul...

Poster TEAP 2015

Most objects can be recognized easily even when they are partly occluded. This also holds when several overlapping objects share the same surface features (self-splitting objects) which is an illustration of the grouping principle of Good Gestalt. We employed outline and filled contour stimuli in a primed flanker task to test whether the processing...

The rapid-chase theory of response priming defines a set of behavioral criteria that indicate feedforward processing of visual stimulus features rather than recurrent processing. These feedforward criteria are strong predictions from a feedforward model that argues that sequentially presented prime and target stimuli lead to strictly sequential wav...

Numerous studies have identified attentional biases and processing enhancements for fear-relevant stimuli in individuals with specific phobias. However, this has not been conclusively shown in blood-injury-injection (BII) phobia, which has rarely been investigated even though it has features distinct from all other specific phobias. The present stu...

Responses to a target can be sped up or slowed down by a congruent or incongruent prime, respectively. Even though presentations are rapid, the prime and the target are thought to activate motor responses in strict sequence, with prime activation preceding target activation. In feature fusion, the opposite seems to be the case. For example, a verni...

We (1) introduce a primed flanker task as an objective method to measure perceptual grouping, and (2) use it to directly compare the efficiency of different grouping cues in rapid visuomotor processing. In two experiments, centrally presented primes were succeeded by flanking targets with varying stimulus-onset asynchronies (SOAs). Primes and targe...

Flanker effects with schematic faces have been reported to be larger for happy than for sad faces, allegedly because sad faces restrict the focus of spatial attention. We report a parametric study that fails to replicate this effect. Participants performed speeded identifications of happy or sad faces accompanied by compatible or incompatible flank...

To pin down the processing characteristics of symmetry and closure in contour processing, we investigated their ability to activate rapid motor responses in a primed flanker task. In three experiments, participants selected as quickly and accurately as possible the one of two target contours possessing symmetry or closure. Target pairs were precede...

Whereas physiological studies indicate that illusory contours (ICs) are signaled in early visual areas at short latencies, behavioral studies are divided as to whether IC processing can proceed in a fast, automatic, bottom-up manner or whether it requires extensive top-down intracortical feedback or even awareness and cognition. Here, we employ a r...

A textbook of Cognitive Psychology, covering the topics of perception, attention, thinking, and language. Part 2 is by Gernot Horstmann & Gesine Dreisbach, "Allgemeine Psychologie 2 kompakt: Lernen, Emotion, Motivation, Gedächtnis", covering learning, memory, motivation, and emotion.

Response priming is a well-understood but sparsely employed paradigm in cognitive science. The method is powerful and well-suited for exploring early visuomotor processing in a wide range of tasks and research fields. Moreover, response priming can be dissociated from visual awareness, possibly because it is based on the first sweep of feedforward...

Whereas neurophysiological studies have shown that illusory contours are signaled in early visual areas at very short latencies, it has been concluded from behavioral studies using backward masking that illusory-contour stimuli have to be present unmasked for at least 100 ms to be perceived and discriminated. In three experiments, we employed a res...

Background / Purpose: Figure-ground perception (FGP) is a complex sequential process initiated by detection of borders and followed by surface enhancement or filling in of the image (Grossberg’s model). Normal perception of figure and ground relies on recurrent processing of signals and is informed by feedback processes. Conversely, border detect...

Visual stimuli can be classified so rapidly that their analysis may be based on a single sweep of feedforward processing through the visuomotor system. Behavioral criteria for feedforward processing can be evaluated in response priming tasks where speeded pointing or keypress responses are performed toward target stimuli which are preceded by prime...

Two experiments employed feature-based attention to modulate the impact of completely masked primes on subsequent pointing responses. Participants processed a color cue to select a pair of possible pointing targets out of multiple targets on the basis of their color, and then pointed to the one of those two targets with a prespecified shape. All ta...

We demonstrate qualitative dissociations of brightness processing in visuomotor priming and conscious vision. Speeded keypress responses to the brighter of two luminance targets were performed in the presence of preceding dark and bright primes (clearly visible and flanking the targets) whose apparent brightness values were enhanced or attenuated b...

Single-cell recordings indicate that a visual stimulus elicits a wave of rapid neuronal activation that propagates so fast that it might be free of intracortical feedback. We traced the time-course of early feedforward activation by measuring pointing responses to color targets preceded by color stimuli priming either the same or opposite response...

We studied how people attribute action outcomes to their own actions under conditions of uncertainty. Participants chose between left and right keypresses to produce an action effect (a corresponding left or right light), while a computer player made a simultaneous keypress decision. In each trial, a random generator determined which of the players...

'Binding' refers to a process whereby separately analyzed features are combined to form a perceptual object. The 'binding problem' arises when features have to be assigned unambiguously to different objects without creating false combinations. Although it is unclear whether binding problems arise in early neural coding, there is solid psychophysica...

Natural images can be classified so rapidly that it has been suggested that their analysis is based on a first single pass of processing activity through the visuomotor system. We tested this theory in a visuomotor priming task in which speeded pointing responses were performed toward one of two target images containing a prespecified stimulus (e.g...

We studied the influence of spatial visual attention on the time course of primed pointing movements. We measured pointing responses to color targets preceded by color stimuli priming either the same response as the target or the opposite response. The effects of visual attention at the prime and target locations were studied by varying both the cu...

Feedforward activation processes are widely regarded as crucial for the automatic initiation of motor responses, whereas recurrent processes are often regarded as crucial for visual awareness. Here, we used a set of behavioral criteria to evaluate whether rapid processing in the human visuomotor system proceeds as would be expected of a feedforward...

Visual masking can be employed to manipulate observers' awareness of critical stimuli in studies of masked priming. This paper discusses two different lines of attack for establishing unconscious cognition in such experiments. Firstly, simple dissociations between direct measures (D) of visual awareness and indirect measures (I) of processing per s...

We investigated the simultaneous effects of different reference systems on spatial memory. Participants studied a configuration of objects surrounding them. During retrieval, they imagined themselves in the center of the object configuration facing a particular object, and then indicated the directions of other objects relative to this imagined hea...

Single-cell recordings have indicated that visual stimuli elicit rapid waves of neuronal activation that propagate so fast that they might be free of intracortical feedback. Here, the time course of feedforward activation was traced by measuring pointing responses to color targets preceded by color primes initiating either the same or opposite resp...

To demonstrate unconscious cognition, researchers commonly compare a direct measure (D) of awareness for a critical stimulus with an indirect measure (I) showing that the stimulus was cognitively processed at all. We discuss and empirically demonstrate three types of dissociation with distinct appearances in D-I plots, in which direct and indirect...

Research on learning under anesthesia has focused on showing that learning is possible in the absence of awareness. However, a simple dissociation between learning and awareness is conclusive only under strong additional assumptions, and the actual state of consciousness of an anesthetized person is difficult to determine. Instead of trying to esta...

Spatial short-term memory for single target positions is subject to distortions which depend on the spatial layout of visual landmarks. Here, participants had to reproduce the positions of briefly presented targets in the context of three-landmark configurations presented in various orientations. Symmetry properties of distortional patterns were de...

We tested the influence of two horizontally aligned visual landmarks on pointing movements to memorized targets, to investigate whether the visuomotor system can make use of an egocentric representation unaffected by visual context. The endpoints of pointing movements were systematically distorted toward the nearest visual landmark, indicating that...

The findings reported in this paper show that perceptual measures based on conscious reports do not suffice to determine whether some information is or is not available to the visual system at large. Instead, motor and perceptual effects can be become perfectly dissociated. This indicates that relevant stimulus attributes are fully processed up to...

Visual landmarks introduce systematic distortions into spatial short-term memory for single target positions, the exact form of the distortion depending on the spatial layout of the landmarks. In two experiments, we investigated how the combined effect of two landmarks can be predicted from the effects of individual landmarks. Participants used a m...

Visual stimuli may remain invisible but nevertheless produce strong and reliable effects on subsequent actions. How well features of a masked prime are perceived depends crucially on its physical parameters and those of the mask. We manipulated the visibility of masked stimuli and contrasted it with their influence on the speed of motor actions, co...

Current theories of dual visual systems suggest that color is processed in a ventral cortical stream that eventually gives rise to visual awareness but is only indirectly involved in visuomotor control mediated by the dorsal stream. If the dorsal stream is indeed less sensitive to color than the ventral stream, color stimuli blocked from awareness...

Memory representations of spatial information require the choice of one or more reference systems to specify spatial relations. In two experiments we investigated the role of different reference systems for the encoding of spatial information in human memory. In Experiment 1, participants had to reproduce the location of a previously seen dot in re...

This book brings together an international group of neuroscientists and philosophers who are investigating how the content of subjective experience is correlated with events in the brain. The fundamental methodological problem in consciousness research is the subjectivity of the target phenomenon—the fact that conscious experience, under standard c...