publications
publications in reversed chronological order.
2024
- The Doorway Effect For An Object Layout Memory Task: An Examination Using Immersive Virtual RealityFlorian FriedrichUniversity of Tübingen, Tübingen, Germany. Master Thesis, grade: 1.3 , May 2024
The “doorway effect” or location updating effect is the decrease in performance for a simple memory task after passing through a doorway. Walking through doorways, according to the Event Horizon Model, constitutes the passing of an event boundary and switching between two mental event models - thus creating an interference effect on memory items. While previous research has consistently demonstrated this effect using a simple memory task, the present study aimed to take a closer look at the robustness of this phenomenon by applying a new, more complex object layout memory task, using a highly immersive virtual reality. No convincing evidence for the presence of a location updating effect could be found, but this study still reveals potential future research opportunities. In particular, using measures of subjective confidence as well as higher working memory loads seems to be a promising direction to examine the generalizability of the “doorway effect” to different memory tasks.
@article{Friedrich_2024, title = {The Doorway Effect For An Object Layout Memory Task: An Examination Using Immersive Virtual Reality}, author = {Friedrich, Florian}, journal = {University of Tübingen}, location = {Tübingen, Germany}, month = may, dimensions = {true}, year = {2024}, doi = {10.17605/OSF.IO/KZ8A6}, url = {https://github.com/floflixt/master-thesis}, }
2022
- Neural mechanisms of response priming do not support veridical unconscious processingConsciousness and Cognition, Jul 2022
Studies using the priming paradigm often infer that unconscious processes have more veridical access to the world than conscious processes. These interpretations are based on a standard reasoning that erroneously infers good sensitivity of indirect measures from a clear priming effect. To correct for this fallacy, researchers should explicitly compute the sensitivities from indirect measures and compare them against the sensitivities of direct measures. Recent results suggest that indirect behavioral measures are not more sensitive than direct measures and challenge interpretations about veridical unconscious processing. We add to these behavioral results by focusing on neurophysiological indirect measures. In two EEG experiments, we investigate whether event related potentials (ERPs) are more sensitive to different visual stimuli than direct measures. The results show the opposite effect: higher sensitivities for direct than indirect measures. Therefore—contrasting commonly held belief—we find no evidence for more veridical unconscious than conscious processes in ERP measures.
@article{Schnepf_2022, title = {Neural mechanisms of response priming do not support veridical unconscious processing}, author = {Schnepf, Iris A. and Friedrich, Florian and Hepting, Christian and Meyen, Sascha and Franz, Volker H.}, journal = {Consciousness and Cognition}, volume = {102}, pages = {103348}, month = jul, year = {2022}, publisher = {Elsevier}, doi = {10.1016/j.concog.2022.103348}, dimensions = {true}, issn = {1053-8100}, url = {https://www.sciencedirect.com/science/article/pii/S1053810022000800} }
2021
- Unconscious priming revisited: Is there evidence for superior unconscious processing with EEG?ECVP, Virtual. Poster presented by I.A. Zerweck , Aug 2021Poster
@article{Zerweck_2021c, title = {Unconscious priming revisited: Is there evidence for superior unconscious processing with EEG?}, author = {Zerweck, Iris A. and Meyen, Sascha and Friedrich, Florian and Hepting, Christian and Franz, Volker H.}, journal = {ECVP}, dimensions = {true}, location = {Virtual}, month = aug, year = {2021}, note = {Poster} } - Effects of visually masked numbers and lines on brain activityJournal of Vision, Sep 2021Poster
A frequently used paradigm to investigate unconscious processing of visual stimuli is masked priming. Traditionally, a direct task is compared to an indirect task: In the direct task, detection of a masked prime stimulus is typically found to be close to chance-level. In the indirect task, effects of the prime on reaction times to a subsequent target stimulus are analyzed (priming effects). Here, we focus on the indirect task and use event-related potentials (ERPs) to examine the effects of the masked primes on brain activity. Previous studies found that early deflections in the lateralized readiness potential (LRP), a measure of specific motor activation, reflect correct and incorrect response activations by the prime. This supports the idea of prime-induced covert motor activations that conflict with the responses required by the target. To test this, we performed two experiments using masked priming with numbers (Exp. 1) and simple line stimuli (Exp. 2). Additionally, in Exp. 1 prime contrast was varied to modulate visibility of the numbers. Preliminary results show that ERP onset latencies for congruent vs. incongruent trials measured at electrode Cz (Exp. 1: normal contrast: M=12 ms, p<.001 / high contrast: M=21 ms, p<.001; Exp. 2: M=51 ms, p<.001) closely matched the behavioral priming effects (Exp. 1: normal contrast: M=9 ms, p<.001 / high contrast: M=21 ms, p=.003; Exp. 2: M=46 ms, p=.001). In addition, we found more negative deflections in the early LRP phase for incongruent as compared to congruent trials in Exp. 2 (albeit not in Exp. 1). Overall, the results support the idea of prime-induced pre-activated motor responses. We discuss differences between the experiments and to which extend the behavioral results are related to the ERP effects.
@article{Zerweck_2021b, title = {Effects of visually masked numbers and lines on brain activity}, author = {Zerweck, Iris A. and Meyen, Sascha and Friedrich, Florian and Hepting, Christian and Franz, Volker H.}, journal = {Journal of Vision}, volume = {21}, issue = {9}, pages = {2293}, month = sep, year = {2021}, dimensions = {true}, note = {Poster}, publisher = {ARVO}, doi = {10.1167/jov.21.9.2293} } - Unconscious priming. Should scientists use continuous direct measures?TeaP, Virtual, TeaP@home. Tagung experimentell arbeitender Psychologen , Mar 2021Talk
A frequently used paradigm to investigate unconscious processing is the masked priming paradigm. Traditionally, a direct task is compared to an indirect task. In the direct task, detection of a masked prime stimulus is measured, typically being close to chance. In the indirect task, effects of the prime on reaction times to a subsequent target stimulus are analyzed (priming effects). Here, we focus on the direct task, where participants usually provide a binary response. In a previous experiment we have shown that confidence covaried with the accuracy of prime detection in number discrimination tasks, suggesting that participants have access to a richer, continuous representation of the prime in the direct task and therefore should not be restricted to a binary decision. To assess whether this remains true for different sets of stimuli, N=11 participants performed the masked priming paradigm with simple line stimuli that were horizontally or vertically oriented. Participants classified the orientation of the prime (direct task) or of the later target stimulus (indirect task). Additionally, in the direct task, participants judged their confidence in their response on a continuous scale. We found that confidence covaried with the accuracy of prime detection (F(1,10)=14.0, p=.004, η²=.58), with higher accuracies of prime detection for trials with higher confidences. We discuss to which extent continuous direct measures open up new analysis strategies and why they might be favorable for the investigation of unconscious priming. [This project is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through the CRC1233 “Robust Vision”, project number 276693517]
@article{Zerweck_2021a, title = {Unconscious priming. Should scientists use continuous direct measures?}, author = {Zerweck, Iris A. and Meyen, Sascha and Friedrich, Florian and Franz, Volker H.}, journal = {TeaP}, location = {Virtual, TeaP@home}, month = mar, year = {2021}, dimensions = {true}, note = {Talk}, publisher = {TeaP} }
2019
- Effects of Visually Entrained Alpha-Frequencies and Individual Alpha Frequencies on Near-Threshold Stimulus Discrimination Task PerformanceFlorian FriedrichUniversity of Tübingen, Tübingen, Germany. Bachelor Thesis, grade: 1.7 , Dec 2019
Rhythmic stimulus presentation is a concept used in multiple sensory modalities and widely used; in the EEG, rhythmic oscillations in the alpha range (7 - 14 Hz) are one of the most prominent patterns. Interindividual differences in these rhythms can be demonstrated, characterizing complex neural activity into an easily measurable marker. Individual resting state alpha frequencies (IAF) and their characteristics (power, phase, frequency) have been shown to correlate with complex cognitive functions, such as the attentional blink (MacLean, Arnell & Cote, 2012) or temporal visual perception (Ronconi, Busch & Melcher, 2018). By presenting rhythmic stimuli, oscillatory activity in the brain can be entrained and subsequentially influences stimulus processing (Mathewson et al., 2012). The present study aimed to examine to what extent IAF and visually entrained frequencies influence the processing of near-threshold (masked) stimuli. No effects of IAF or entrainment to different frequencies (8, 12, 30 Hz) could be found. This result demonstrates that the frequency of rhythmic brain activity itself did not prove to be a reliable indicator of the temporal resolution of the visual system in the discrimination task used here. The speed of visual processing as examined by briefly presented masked stimuli does not seem to be connected to the dominant alpha frequencies during resting states. Further examination of IAF and visual alpha oscillations is required to examine their connection to the speed of visual processing.
@article{Friedrich_2019, title = {Effects of Visually Entrained Alpha-Frequencies and Individual Alpha Frequencies on Near-Threshold Stimulus Discrimination Task Performance}, author = {Friedrich, Florian}, journal = {University of Tübingen}, location = {Tübingen, Germany}, month = dec, year = {2019}, dimensions = {true}, }
2018
- Evaluating methods in visual tasks: Confidence ratings convey more information than binary responsesECVP, Triest, Italy. 41st European Conference on Visual Perception , Aug 2018Poster
To investigate unconscious processing, researchers often present sequences of different stimuli (mask, prime, target) and compare two tasks: In the direct task, participants directly respond to a masked prime. In the indirect task, participants respond to a target preceded by the masked prime. Typically, the prime has effects on reaction times in the indirect task, which is interpreted as preserved unconscious processing of the prime. However, this paradigm is problematic, because participants are restricted to a binary response in the direct task. 12 participants gave a binary response and also judged their confidence on a continuous scale. We found that confidence modulated the accuracy of prime detection: Overall accuracy (mean+/-SEM in percent): 58.6+/-1.4; accuracy in high/low- confidence trials: 64.4+/-2.1 / 53.5+/-1.1. We also applied classic information theory and found that the higher accuracies in high/low confidence trials increased the overall information about the prime.
@article{Zerweck_2018b, title = {Evaluating methods in visual tasks: Confidence ratings convey more information than binary responses}, author = {Zerweck, Iris A. and Meyen, Sascha and Amado, Catarina and Friedrich, Florian and Franz, Volker H.}, journal = {ECVP}, location = {Triest, Italy}, month = aug, year = {2018}, note = {Poster}, dimensions = {true}, publisher = {ECVP} } - Unconscious processing of numbers: How important is the response format?TeaP, Marburg, Germany. Tagung experimentell arbeitender Psychologen , Mar 2018Poster
To evaluate unconscious processing of numbers, we used a classic priming paradigm: In a ‘direct’ task, participants classified a masked ‘prime’-stimulus (i.e., decided whether it is a number larger or smaller than 5). In this task, participants typically perform close to chance, suggesting no conscious awareness of the prime. In an ‘indirect’ task, the masked prime was also presented, but participants responded to another stimulus (decided whether that number was larger or smaller than 5). Typically, the prime has effects on reaction times in the indirect task, which is usually interpreted as preserved unconscious processing of the prime. However, this paradigm could be problematic, because participants are restricted to a binary response in the direct task. To assess whether participants have access to a richer, continuous representation of the prime in the direct task, we had 12 participants give a binary response and also judge their confidence on a continuous scale. We found that confidence modulated the accuracy of prime detection: Overall accuracy (mean+/-SEM in percent): 58.6+/-1.4; accuracy in high/low-confidence trials: 64.4+/-2.1 / 53.5+/-1.1, respectively. We will discuss to which degree this effect could be exploited to improve the response format in such paradigms.
@article{Zerweck_2018a, title = {Unconscious processing of numbers: How important is the response format?}, author = {Zerweck, Iris A. and Meyen, Sascha and Friedrich, Florian and Grethen, Klara and Franz, Volker H.}, journal = {TeaP}, location = {Marburg, Germany}, month = mar, year = {2018}, note = {Poster}, dimensions = {true}, publisher = {TeaP} }