Pietro Amerio

A central challenge in consciousness research is to dissociate perception from awareness using rigorous, bias-free methods. Traditional approaches often suffer from two key limitations: the criterion biases in reporting perceptual (un)awareness, and the criterion content fallacy, where awareness measures do not capture the specific information required to perform the perceptual task. These problems are compounded by the widespread use of single-object paradigms, which typically involve presenting isolated stimuli near threshold and suppressing them with masking techniques. These constraints result in a low signal-to-noise ratio that severely limits sensitivity to detect effects and offers low ecological validity. Here, we introduce a novel paradigm based on ensemble perception that overcomes these long-standing limitations. Experiment 1 used a bias-free two-interval forced-choice task in which observers had to discriminate the predominant category in ensembles comprising animate and inanimate items and also detect which interval contained the task-relevant features. Experiment 2 extended these findings with a single-interval design, addressing concerns about potential detection inefficiencies. Multiple control analyses across experiments demonstrate unconscious ensemble perception: observers reliably discriminated ensemble-level properties even when detection of the task-relevant features was at chance. Convolutional neural network simulations further showed that this dissociation can arise from weak ensemble-level evidence, supporting discrimination even when detection fails. Bayesian ideal observer modeling situated these findings within a formal computational account of unconscious perception. Together, our findings demonstrate that perceptual processing of complex visual summaries can occur without conscious awareness. The work offers a new framework for studying visual consciousness beyond the limits of traditional single-target paradigms.

Outliers can strongly change statistical results, yet the three most widely used methods in psychology and neuroscience to detect them, Standard Deviation (SD), Interquartile Range (IQR), and Median Absolute Deviation (MAD), do not perform equally well across different data conditions. Importantly, these methods have rarely been compared systematically across a broad set of realistic scenarios, making it difficult for researchers to select an appropriate method in advance.In this study, we conducted large-scale simulations that varied distributional shape (normal, asymmetric, leptokurtic, uniform, asymmetric bimodal), sample size, outlier placement and outlier rate (0–40%). For each scenario, we assessed how SD, IQR, and MAD classified data points as valid or outlying by computing an accuracy score.Across the classic approaches, the most effective fixed thresholds were 2 SD, 2 IQR, and 3 MAD. SD performed well only when outliers were extremely rare (0-6%), but its accuracy dropped sharply as contamination increased. IQR was more robust at moderate outlier rates (8-20%), yet it became unreliable when many outliers were present or when distributions were uniform or bimodal. MAD showed the highest accuracy at high contamination levels (22-40%), although in leptokurtic (heavy-tailed) distributions both MAD and IQR were more biased than SD.To address these limitations, we introduce the MAD–IQR–SD Simultaneous (MISS) method, which integrates the three classical statistics using optimized weights identified through a genetic algorithm: 1.5 MAD [87.8%], 1 IQR [1.2%], 5 SD [11%]. Across all simulations, MISS achieved the highest overall accuracy (97.4%) and outperformed each classical method across most contexts.

Although in recent years some studies have found evidence suggesting that working memory (WM) may operate on unconscious perceptual contents, decisive demonstrations of the existence of unconscious WM are lacking. In the present Registered Report, we replicate the first study on this topic by Soto et al. (Working memory without consciousness. Curr Biol 2011;21:R912–3.): a visual discrimination task asking participants to report the direction in which a subliminal Gabor grating was rotated after a 2-s delay. We acquired a multisite sample from 19 laboratories, with a larger number of participants (N = 531) and trials (720 in two sessions) than those typically used in previous studies. As a result, a large-sample, international, and open-access dataset is now available for researchers and future analyses. Furthermore, some minimal baseline requirements were guaranteed for the experimental task (i.e. number of valid trials, motivation, and consistent labels for the Perceptual Awareness Scale). The results showed (1) above-chance WM performance in cue-present trials reported as unseen (.55 accuracy), (2) a significant positive correlation between WM performance and cue detection sensitivity (r = .228), and (3) a significant above-chance intercept in the regression of performance on sensitivity (β0 = .521). These findings suggest that WM can operate on unconscious representations, although it remains positively associated with perceptual sensitivity. Crucially, because measurement error could compromise the interpretation of these three results, we provide evidence for our measures’ excellent reliability and, more fundamentally, for their validity.

Although in recent years some studies have found evidence suggesting that Working Memory (WM) may operate on unconscious perceptual contents, decisive demonstrations of the existence of unconscious WM are lacking. In the present Registered Report, we replicate the first study on this topic by Soto et al. (2011): a visual discrimination task asking participants to report the direction in which a subliminal Gabor grating was rotated after a 2-second delay. We acquired a multisite sample from 19 laboratories, with a larger number of participants (N = 531) and trials (720 in two sessions) than those typically used in previous studies. As a result, a large-sample, international, and open-access dataset is now available for researchers and future analyses. Furthermore, some minimal baseline requirements were guaranteed for the experimental task (i.e., number of valid trials, motivation, and consistent labels for the Perceptual Awareness Scale). The results showed: (1) above-chance WM performance in cue- present trials reported as unseen (.55 accuracy), (2) a significant positive correlation between WM performance and cue detection sensitivity (r = .228), and (3) a significant above-chance intercept in the regression of performance on sensitivity (β0 = .521). These findings suggest that WM can operate on unconscious representations, although it remains positively associated with perceptual sensitivity. Crucially, because measurement error could compromise the interpretation of these three results, we provide evidence for our measures’ excellent reliability and, more fundamentally, for their validity.

Perceiving a brief visual stimulus depends on both its intensity and its exposure duration.These two parameters are in a reciprocal relationship, such that doubling the duration andhalving the intensity of a stimulus leads to equivalent perceptual performance. Thisrelationship is known as Bloch’s law. Despite numerous demonstrations of the validity ofBloch’s law, recent evidence shows violations for exposures ranging from few microsecondsto tens of milliseconds. The main goal of this work was to reassess the law’s validity on theperception of simple geometric shapes. The latter were presented for durations between0.15 and 100 ms thanks to a modern LCD-based tachistoscope. We successfully replicatedthe reciprocal relationship between intensity and duration across five different tasksinvolving detection, shape discrimination and subjective visibility judgements. In accordancewith past literature, we report reciprocity only for stimuli shorter than a maximum criticalduration (between 15 and 36 ms, depending on the task). We discuss these results incomparison with the aforementioned violations of Bloch’s law, and identify potential causesof the latter. This work also served as a proof-of-principle that our apparatus is suitable forthe study of the intensity-duration reciprocity with a diverse range of stimuli.

The scope of unconscious processing has long been, and still remains, a hotly debated issue. This is driven in part by the current diversity of methods to manipulate and measure perceptual consciousness. Here, we provide ten recommendations and nine outstanding issues about designing experimental paradigms, analyzing data, and reporting the results of studies on unconscious processing. These were formed through dialogue among a group of researchers representing a range of theoretical backgrounds. We acknowledge that some of these recommendations naturally do not align with some existing approaches and are likely to change following theoretical and methodological development. Nevertheless, we hold that at this stage of the field they are instrumental in evoking a much-needed discussion about the norms of studying unconscious processes and helping researchers make more informed decisions when designing experiments. In the long run, we aim for this paper and future discussions around the outstanding issues to lead to a more convergent corpus of knowledge about the extent – and limits – of unconscious processing.

The scope of unconscious processing has long been, and still remains, a hotly debated issue. This is driven in part by the current diversity of methods to manipulate and measure perceptual consciousness. We provide here ten recommendations and nine outstanding issues about designing experimental paradigms, analyzing data, and reporting the results of studies on unconscious processing. These were formed through dialogue among a group of researchers representing a range of theoretical backgrounds. We acknowledge that some of these recommendations naturally do not align with some existing approaches and are likely to change following theoretical and methodological development. Nevertheless, we hold that at this stage of the field they are instrumental in evoking a much-needed discussion about the norms of studying unconscious processes and helping researchers make more informed decisions when designing experiments. In the long run, we aim for this paper and future discussions around the outstanding issues to lead to a more convergent corpus of knowledge about the extent – and limits – of unconscious processing.

The comparison between conscious and unconscious perception is a cornerstone of consciousness science. However, most studies reporting above-chance discrimination of unseen stimuli do not control for criterion biases when assessing awareness. We tested whether observers can discriminate subjectively invisible offsets of Vernier stimuli when visibility is probed using a bias-free task. To reduce visibility, stimuli were either backward masked or presented for very brief durations (1–3 milliseconds) using a modern-day Tachistoscope. We found some behavioral indicators of perception without awareness, and yet, no conclusive evidence thereof. To seek more decisive proof, we simulated a series of Bayesian observer models, including some that produce visibility judgements alongside type-1 judgements. Our data are best accounted for by observers with slightly suboptimal conscious access to sensory evidence. Overall, the stimuli and visibility manipulations employed here induced mild instances of blindsight-like behavior, making them attractive candidates for future investigation of this phenomenon.

Creating an integrated design space can be successful only if researchers agree on how to define and measure a certain phenomenon of interest. Adversarial collaborations and mathematical modeling can aid in reaching the necessary level of agreement when researchers depart from different theoretical perspectives.