Previous research has shown that higher-level cognitive processes like attention, memory or mental imagery can produce pupil responses, without any actual difference in luminance of the visual stimulus. Interestingly, the inverse scenario remains untested: when a difference in luminance is perceptually eliminated from awareness, does pupil size still track cognitive factors? In this study, Vilotijević and Mathôt (2024) seek to test this experimentally using a perceptual fading phenomenon where two Gaussian patches with different luminances fade from consciousness and are thus perceived as mid-level uniform grey. The researchers will present this fading manipulation and a control condition where no fading occurs in separate blocks. Participants are instructed to covertly attend one of the patches. If pupil size reflects attentional selection, pupil responses should be reduced in the fading condition, and this should evolve with time as the stimuli are perceptually fading.

 

The Stage 1 manuscript was evaluated by three reviewers and the Recommender over three rounds of review. One reviewer advises conducting robustness checks to rule out eye movements confounds. This constitutes exploratory analyses at Stage 2 that probably require some flexibility. Despite this, the Recommender decided to grant in-principle acceptance of this study. While these robustness tests can put the eventual results in context, the general hypotheses and predictions specified in this version are clear and straightforward.

 

URL to the preregistered Stage 1 protocol: https://osf.io/bmtp6
 
Level of bias control achieved: Level 6. No part of the data or evidence that will be used to answer the research question yet exists and no part will be generated until after IPA.
 
List of eligible PCI RR-friendly journals:

 

 

 

1. Vilotijević, A. & Mathôt, S. (2024). The effect of covert visual attention on pupil size during perceptual fading. In principle acceptance of Version 3 by Peer Community in Registered Reports. https://osf.io/bmtp6

 

Much of how we use our perception involves judgements on how similar things are: You might vaguely recognise an actor's face in a movie but not immediately recognise where you have seen it before. Some people claim to be "bad with faces". Is that in fact based on objectively poorer ability to recognise faces? Psychophysical lab studies of perception typically use forced-choice discrimination tasks in which participants must make explicit, and usually binary, decisions. Such designs can yield parametric information about underlying perceptual processes, but it is very different from how we use perception in daily life.

 

Here, Moharramipour and colleagues (2024) seek to better understand the link between such subjective similarity jugdements and objective discrimination ability. They argue that subjective similarity can be considered a metacognitive process, reflecting the person's awareness of their perceptual capacity. Participants will be asked to discriminate face pairs across a spectrum of morphing steps in a classical forced-choice paradigm to estimate perceptual threshold performance, as well as provide subjective ratings of similarity of the face pairs. The researchers hypothesise a correlation between objective perceptual ability and subjective similarity judgements. They will evaluate this at the group level, and also use a resampling approach to determine the specificity of this relationship in individual participants. Confirming this hypothesis would advance our knowledge of how perceptual ability links with our metacognitive introspection of it. Are you really "bad with faces" or do you only think you are?

 

The Stage 1 manuscript was evaluated over two rounds of in-depth review. Based on detailed responses to the reviewers' comments, the recommender judged that the manuscript met the Stage 1 criteria and awarded in-principle acceptance (IPA).

 

URL to the preregistered Stage 1 protocol: https://osf.io/pzugy
 
Level of bias control achieved: Level 6. No part of the data or evidence that will be used to answer the research question yet exists and no part will be generated until after IPA.
 
List of eligible PCI RR-friendly journals: 

 

 

Moharramipour, A., Zhou, W., Rahnev, D., & Lau, H. (2024). Is subjective perceptual similarity metacognitive? In principle acceptance of Version 4 by Peer Community in Registered Reports. https://osf.io/pzugy

Loneliness is increasingly a focus of governments and health systems due to its potential adverse effects. Various ways to measure it have been developed but the psychometric properties of common instruments have not yet been evaluated across all countries in the European Union (EU).

 

In this study, Paris et al. (2025) will examine three measures of loneliness across 27 EU member countries. An online survey (n = 25,646) incorporated three instruments which were translated into national languages: the De Jong Gierveld Loneliness Scale (6 items), the three-item UCLA Loneliness Scale (3 items), and a single-item measure (“How much of the time, during the past 4 weeks, have you been feeling lonely”). The factor structure, internal consistency, and measurement invariance for the 6- and 3-item measures will be assessed, as well as the construct validity of all three measures using nomological networks. The authors have adopted an n-fold procedure to analyse the data, with a first exploratory fold using half of the data to establish hypotheses for each question and a second confirmatory fold using the remainder of the data to test the hypotheses. The results of the study will provide important information about the psychometric properties of commonly used loneliness instruments, and can indicate which measures are appropriate for loneliness monitoring across the EU.

 

The study plan was refined across four rounds of in-depth review with input from four reviewers, Thuy-vy Nguyen, Joe Bathelt, Mary Louise Pomeroy, and Drew Altschul, and the recommenders, after which it was judged to meet the Stage 1 criteria and received in-principle acceptance.
 
URL to the preregistered Stage 1 protocol: https://osf.io/2s38v

 
Level of bias control achieved: Level 3. At least some data/evidence that will be used to the answer the research question has been previously accessed by the authors (e.g. downloaded or otherwise received), but the authors certify that they have not yet observed ANY part of the data/evidence
 
List of eligible PCI RR-friendly journals:
 

 

 

Paris, B., Ropovik, I., Silan, M., d'Hombres, B., Casabianca, E., & IJzerman, H. (2025). Evaluating Loneliness Measurements across the European Union. In principle acceptance of Version 4 by Peer Community in Reigstered Reports. https://osf.io/2s38v

 

Previous research has demonstrated that experimental participants – both adults and infants – can track syllable co-occurrences in an artificial speech stream. This statistical learning (SL) is thought to support word segmentation and to be a core component of language acquisition. There is also some evidence that SL, as measured through artificial language tasks, is related to individual differences in language learning. What is not well understood is the underpinnings of individual differences in SL. In the current study, van der Wulp et al. (2023) will investigate the relationship between auditory SL and musical – specifically rhythmic – abilities. This work takes advantage of recent methodological innovations which allow online assessment of SL via electroencephalography (EEG) measures of neural entrainment. Up to N=105 participants will be recruited (using a well specified optional stopping procedure) and will be exposed to an artificial language using this EEG method to measure their response to the language through the exposure phase. In addition, post-tests will assess participants’ learning of the artificial language using behavioural tasks, as well as their abilities in a battery of tasks measuring rhythmic, musical, and cognitive abilities, and their vocabulary size. Core analyses will investigate whether the neural signature of statistical learning is found at a group level (i.e. replicating previous work) and whether at the individual level this is related to rhythm perception. Bayes factors will be used to assess the extent of evidence for these hypothesized relationships over the null. Exploratory analyses will explore other relationships, including with working memory and vocabulary size. 

 

The topic of individual differences in language learning and is important, but work in this area is often underpowered, and the correlational nature of the research makes it vulnerable to HARKing. In this context, the current RR looks set to make an important contribution. The Stage 1 manuscript was evaluated over two rounds of in-depth review by the recommender and two expert reviewers, and one additional round of review by the recommender, before issuing in-principle acceptance.

 

Level of bias control achieved: Level 6. No part of the data or evidence that will be used to answer the research question yet exists and no part will be generated until after IPA.
 
List of eligible PCI RR-friendly journals:
 

• Advances in Cognitive Psychology
• Brain and Neuroscience Advances
• Collabra: Psychology
• Cortex
• Experimental Psychology
  
• Imaging Neuroscience
• In&Vertebrates
• Journal of Cognition
• NeuroImage: Reports
• Peer Community Journal
• PeerJ
• Royal Society Open Science
• Studia Psychologica

 

References
 
1. van der Wulp, I. M., Struiksma, M. E., Batterink, L. J., & Wijnen, F. N. K. (2023). Investigating individual differences in linguistic statistical learning and their relation to rhythmic and cognitive abilities: A speech segmentation experiment with online neural tracking. In principle acceptance of Version 4 by Peer Community in Registered Reports. https://osf.io/2y6sx

 

 

Over the past decade there has been an exponential increase in the number of research papers utlising nanoparticles for biological applications such as intracellular sensing [1, 2], theranostics [3-5] and more recently drug delivery and precision medicine [6, 7]. Despite the success stories, there is a disconnect regarding current dogma on issues such as nanoparticle uptake and trafficking, nanoparticle delivery via the enhanced permeability and retention (EPR) effect, and endosomal escape. Critical re-evaluation of these concepts both conceptually and experimentally is needed for continued advancement in the field.

 

For this preregistration, Said et al. (2024) focus on nanoparticle intracellular trafficking, specifically endosomal escape [8]. The current consensus in the literature is that nanoparticles enter cells via endocytosis [9, 10] but reportedly just 1-2% of nanoparticles/ nanoparticle probes escape endosomes and enter the cytoplasm [11-13]. There is therefore an apparent paradox over how sensing nanoparticles can detect their intended targets in the cytoplasm if they are trapped within the cell endosomes. To address this fundamental issue of nanoparticle endosomal escape, Lévy and coworkers are carrying out replication studies to thoroughly and transparently replicate the most influential papers in the field of nanoparticle sensing. The aim of these replication studies is twofold: to establish a robust methodology to study endosomal escape of nanoparticles, and to encourage discussions, transparency and a step-change in the field.  

 

 

For this replication study, the authors classified papers on the topic of nanoparticle sensing and subsequently ranked them by number of citations.  Based on this evaluation they selected a paper by Zhu and colleagues [14] entitled “Carbon-Dot-Based Dual-Emission Nanohybrid Produces a Ratiometric Fluorescent Sensor for In Vivo Imaging of Cellular Copper Ions” for their seminal replication study.  To determine the reproducibility of the results from Zhu et al., the authors aim to establish the proportion of endosomal escape of the nanoparticles, and to examine the data in a biological context relevant to the application of the probe.

 

 

The authors plan to replicate the exact conditions reported in the materials and methods section of the selected paper such as nanoparticle probe synthesis of CdSe@C-TPEA nanoparticles, assessment of particle size, stability and reactivity and effect on cells (TEM, pH experiments, fluorescent responsivity to metal ions and cell viability). In addition, Said et al., plan to include further experimental characterisation to complement the existing study by Zhu and colleagues. They will incorporate additional controls and methodology to determine the intracellular location of nanoparticle probes in cells including: quantifying excess fluorescence in the culture medium, live cell imaging analysis, immunofluorescence with endosomal and lysosomal markers, and electron microscopy of cell sections. The authors will also include supplementary viability studies to assess the impact of the nanoparticles on HeLa cells as well as an additional biologically relevant cell line (for use in conjunction with the HeLa cells as per the original paper).

 

The Stage 1 manuscript underwent two rounds of thorough in-depth review. After considering the detailed responses to the reviewers' comments, the recommenders  determined that the manuscript met the Stage 1 criteria and awarded in-principle acceptance (IPA).  

 

The authors have thoughtfully considered their experimental approach to the replication study, whilst acknowledging any potential limitations. Given that conducting such a replication study is novel in the field of Nanotechnology and there is currently no ‘gold standard’ approach in doing so, the authors have showed thoughtful regard of statistical analysis and unbiased methodology where possible.

 

Based on current information, this study is the first use of preregistration via Peer Community in Registered Reports and the first formalised replication study in Nanotechnology for Biosciences. The outcomes of this of this study will be significant both scientifically and in the wider context in discussion of the scientific method.

 

 
Level of bias control achieved: Level 6. No part of the data or evidence that will be used to answer the research question yet exists and no part will be generated until after IPA.
 
List of eligible PCI RR-friendly Journals:

 

 

1. Howes, P. D., Chandrawati, R., & Stevens, M. M. (2014). Colloidal nanoparticles as advanced biological sensors. Science, 346(6205), 1247390. https://doi.org/10.1126/science.1247390

 

2. Liu, C. G., Han, Y. H., Kankala, R. K., Wang, S. B., & Chen, A. Z. (2020). Subcellular performance of nanoparticles in cancer therapy. International Journal of Nanomedicine, 675-704. https://doi.org/10.2147/IJN.S226186

 

3. Tang, W., Fan, W., Lau, J., Deng, L., Shen, Z., & Chen, X. (2019). Emerging blood–brain-barrier-crossing nanotechnology for brain cancer theranostics. Chemical Society Reviews, 48(11), 2967-3014. https://doi.org/10.1039/C8CS00805A

 

4. Yoon, Y. I., Pang, X., Jung, S., Zhang, G., Kong, M., Liu, G., & Chen, X. (2018). Smart gold nanoparticle-stabilized ultrasound microbubbles as cancer theranostics. Journal of Materials Chemistry B, 6(20), 3235-3239. https://doi.org/10.1039%2FC8TB00368H

 

5. Lin, H., Chen, Y., & Shi, J. (2018). Nanoparticle-triggered in situ catalytic chemical reactions for tumour-specific therapy. Chemical Society Reviews, 47(6), 1938-1958. https://doi.org/10.1039/C7CS00471K

 

6. Hou, X., Zaks, T., Langer, R., & Dong, Y. (2021). Lipid nanoparticles for mRNA delivery. Nature Reviews Materials, 6(12), 1078-1094. https://doi.org/10.1038/s41578-021-00358-0

 

7. Mitchell, M. J., Billingsley, M. M., Haley, R. M., Wechsler, M. E., Peppas, N. A., & Langer, R. (2021). Engineering precision nanoparticles for drug delivery. Nature Reviews Drug Discovery, 20(2), 101-124. https://doi.org/10.1038/s41573-020-0090-8

 

8. Said, M., Gharib, M., Zrig, S., & Lévy, R. (2024). Replication of “Carbon-Dot-Based Dual-Emission Nanohybrid Produces a Ratiometric Fluorescent Sensor for In Vivo Imaging of Cellular Copper Ions”. In principle acceptance of Version 3 by Peer Community in Registered Reports. https://osf.io/qbxpf

 

9. Behzadi, S., Serpooshan, V., Tao, W., Hamaly, M. A., Alkawareek, M. Y., Dreaden, E. C., ... & Mahmoudi, M. (2017). Cellular uptake of nanoparticles: Journey inside the cell. Chemical Society Reviews, 46(14), 4218-4244. https://doi.org/10.1039/C6CS00636A

 

10. de Almeida, M. S., Susnik, E., Drasler, B., Taladriz-Blanco, P., Petri-Fink, A., & Rothen-Rutishauser, B. (2021). Understanding nanoparticle endocytosis to improve targeting strategies in nanomedicine. Chemical society reviews, 50(9), 5397-5434. https://doi.org/10.1039/D0CS01127D

 

11. Smith, S. A., Selby, L. I., Johnston, A. P., & Such, G. K. (2018). The endosomal escape of nanoparticles: toward more efficient cellular delivery. Bioconjugate Chemistry, 30(2), 263-272. http://dx.doi.org/10.1021/acs.bioconjchem.8b00732

 

12. Cupic, K. I., Rennick, J. J., Johnston, A. P., & Such, G. K. (2019). Controlling endosomal escape using nanoparticle composition: current progress and future perspectives. Nanomedicine, 14(2), 215-223. https://doi.org/10.2217/nnm-2018-0326

 

13. Wang, Y., & Huang, L. (2013). A window onto siRNA delivery. Nature Biotechnology, 31(7), 611-612. https://doi.org/10.1038/nbt.2634

 

14. Zhu, A., Qu, Q., Shao, X., Kong, B., & Tian, Y. (2012). Carbon-dot-based dual-emission nanohybrid produces a ratiometric fluorescent sensor for in vivo imaging of cellular copper ions. Angewandte Chemie (International ed. in English), 51(29), 7185-7189. https://doi.org/10.1002/anie.201109089