| A selection of publications sorted by year |
| 2025 |
| Abstract: | Mathematics is an underexplored domain of human cognition. While many studies have focused on subsets of math concepts such as numbers, fractions, or geometric shapes, few have ventured beyond these elementary domains. Here, we attempted to map out the full space of math concepts and to answer two specific questions: can distributed semantic models, such a GloVe, provide a satisfactory fit to human semantic judgements in mathematics? And how does this fit vary with education? We first analyzed all of the French and English Wikipedia pages with math contents, and used a semi-automatic procedure to extract the 1000 most frequent math terms in both languages. In a second step, we collected extensive behavioral judgements of familiarity and semantic similarity between them. About half of the variance in human similarity judgements was explained by vector embeddings that attempt to capture latent semantic structures based on cooccurence statistics. Participants' self-reported level of education modulated familiarity and similarity, allowing us to create a partial hierarchy among high-level math concepts. Our results converge onto the proposal of a map of math space, organized as a database of math terms with information about their frequency, familiarity, grade of acquisition, and entanglement with other concepts. |
| Abstract: | ABSTRACT At the physical level, the experience of pitch has a single determinant: the repetition rate of a waveform in the acoustic signal. Yet, psychologists describe pitch as composed of two perceptual dimensions, height and chroma. Chroma accounts for octave equivalence, whereby sounds with fundamental frequencies at a 1:2 ratio are perceived as sharing the same pitch. A current controversy debates whether chroma is a basic perceptual property dependent on biological constraints or a higher-order cognitive construct shaped by culture. Here, we used high-density electroencephalography (EEG) and time-resolved multivariate pattern analyses to characterize pitch processing in humans at 3 months of age. We found that, when exposed to repetitive sequences of orchestral tones, infants encode two separate pitch-related dimensions automatically and with divergent dynamics. Namely, our classifiers isolated height-specific information from the neural signal rapidly after the onset of the auditory sequences. Beyond approximately 600 ms, the performance of pitch height decoders fell to chance level and did not recover. In contrast, neural patterns displaying octave equivalence were retrieved later in the trial, over multiple time windows throughout the unfolding of the auditory sequence, and after sequence offset. Overall, this study reveals that very early in human development, the pitch of naturally rich tones is processed over two distinct encoding stages, capturing not only their absolute height but also their relative position in the octave. We speculate that separate encoding mechanisms reflect distinct functional roles carried by the two dimensions. |
| Abstract: | Around the world, teenage boys outperform girls on mathematics tests, and men are more likely to pursue related careers -- despite baby boys showing no superior sense of numbers or grasp of logic. Now, a gigantic study of schoolchildren in France pinpoints that this 'mathematical gender gap' appears during the first year of school. The finding could help to focus efforts to stop girls from falling behind. Boys and girls receive similar maths scores at the start of school, but boys pull ahead of girls after just four months (see 'Watch the mathematics gender gap emerge'). A more dramatic gap in mathematical performance emerges after 12 months of school, according to the analysis, published on 11 June in Nature1. "This paper suggests that the gender inequalities in children's maths performance aren't innate or inevitable," says psychologist Jillian Lauer at the University of Cambridge, UK. "If we want to stop girls from falling behind, we need to focus on their early experiences at school." |
| 2024 |
| Abstract: | Over the past decade, studies of naturalistic language processing where participants are scanned while listening to continuous text have flourished. Using word embeddings at first, then large language models, researchers have created encoding models to analyze the brain signals. Presenting these models with the same text as the participants allows to identify brain areas where there is a significant correlation between the functional magnetic resonance imaging (fMRI) time series and the ones predicted by the models' artificial neurons. One intriguing finding from these studies is that they have revealed highly symmetric bilateral activation patterns, somewhat at odds with the well-known left lateralization of language processing. Here, we report analyses of an fMRI dataset where we manipulate the complexity of large language models, testing 28 pretrained models from 8 different families, ranging from 124M to 14.2B parameters. First, we observe that the performance of models in predicting brain responses follows a scaling law, where the fit with brain activity increases linearly with the logarithm of the number of parameters of the model (and its performance on natural language processing tasks). Second, although this effect is present in both hemispheres, it is stronger in the left than in the right hemisphere. Specifically, the left-right difference in brain correlation follows a scaling law with the number of parameters. This finding reconciles computational analyses of brain activity using large language models with the classic observation from aphasic patients showing left hemisphere dominance for language. |
| Abstract: | The understanding of the human brain is one of the main scientific challenges of the twenty-first century. In the early 2000s, the French Atomic Energy Commission launched a program to conceive and build a human magnetic resonance imaging scanner operating at 11.7 T. We have now acquired human brain images in vivo at such a magnetic field. We deployed parallel transmission tools to mitigate the radiofrequency field inhomogeneity problem and tame the specific absorption rate. The safety of human imaging at such high field strength was demonstrated using physiological, vestibular, behavioral and genotoxicity measurements on the imaged volunteers. Our technology yields T2 and T2*-weighted images reaching mesoscale resolutions within short acquisition times and with a high signal and contrast-to-noise ratio. |
| Abstract: | The brain constantly uses prior knowledge of the statistics of its environment to shape perception. These statistics are often implicit (not directly observable) and learned incrementally from observation, but they can also be explicitly communicated to the observer, especially in humans. Here, we show that priors are used differently in human perceptual inference depending on whether they are explicit or implicit in the environment. Bayesian modeling of learning and perception revealed that the weight of the sensory likelihood in perceptual decisions was highly correlated across participants between tasks with implicit and explicit priors, and slightly stronger in the implicit task. By contrast, the weight of priors was much less correlated across tasks, and it was markedly smaller for explicit priors. The model comparison also showed that different computations underpinned perceptual decisions depending on the origin of the priors. This dissociation may resolve previously conflicting results about the appropriate use of priors in human perception. |
| Abstract: | A central feature in music is the hierarchical organization of its components. Musical pieces are not a simple concatenation of chords, but are characterized by rhythmic and harmonic structures. Here, we explore if sensitivity to music structure might emerge in the absence of any experience with musical stimuli. For this, we tested if rats detect the difference between structured and unstructured musical excerpts and compared their performance with that of humans. Structured melodies were excerpts of Mozart's sonatas. Unstructured melodies were created by the recombination of fragments of different sonatas. We trained listeners (both human participants and Long-Evans rats) with a set of structured and unstructured excerpts, and tested them with completely novel excerpts they had not heard before. After hundreds of training trials, rats were able to tell apart novel structured from unstructured melodies. Human listeners required only a few trials to reach better performance than rats. Interestingly, such performance was increased in humans when tonality changes were included, while it decreased to chance in rats. Our results suggest that, with enough training, rats might learn to discriminate acoustic differences differentiating hierarchical music structures from unstructured excerpts. More importantly, the results point toward species-specific adaptations on how tonality is processed. |
| Abstract: | William James's use of "time in passing" and "stream of thoughts" may be two sides of the same coin that emerge from the brain segmenting the continuous flow of information into discrete events. Herein, we investigated how the density of events affects two temporal experiences: the felt duration and speed of time. Using a temporal bisection task, participants classified seconds-long videos of naturalistic scenes as short or long (duration), or slow or fast (passage of time). Videos contained a varying number and type of events. We found that a large number of events lengthened subjective duration and accelerated the felt passage of time. Surprisingly, participants were also faster at estimating their felt passage of time compared to duration. The perception of duration scaled with duration and event density, whereas the felt passage of time scaled with the rate of change. Altogether, our results suggest that distinct mechanisms underlie these two experiential times. |
| Abstract: | seudowords are letter strings that look like words but are not words. They are used in psycholinguistic research, particularly in tasks such as lexical decision. In this context, it is essential that the pseudowords respect the orthographic statistics of the target language. Pseudowords that violate them would be too easy to reject in a lexical decision and would not enforce word recognition on real words. We propose a new pseudoword generator, UniPseudo, using an algorithm based on Markov chains of orthographic n-grams. It generates pseudowords from a customizable database, which allows one to control the characteristics of the items. It can produce pseudowords in any language, in orthographic or phonological form. It is possible to generate pseudowords with specific characteristics, such as frequency of letters, bigrams, trigrams, or quadrigrams, number of syllables, frequency of biphones, and number of morphemes. Thus, from a list of words composed of verbs, nouns, adjectives, or adverbs, UniPseudo can create pseudowords resembling verbs, nouns, adjectives, or adverbs in any language using an alphabetic or syllabic system. |
| Abstract: | Decision-making in noisy, changing, and partially observable environments entails a basic tradeoff between immediate reward and longer-term information gain, known as the exploration-exploitation dilemma. Computationally, an effective way to balance this tradeoff is by leveraging uncertainty to guide exploration. Yet, in humans, empirical findings are mixed, from suggesting uncertainty-seeking to indifference and avoidance. In a novel bandit task that better captures uncertainty-driven behavior, we find multiple roles for uncertainty in human choices. First, stable and psychologically meaningful individual differences in uncertainty preferences actually range from seeking to avoidance, which can manifest as null group-level effects. Second, uncertainty modulates the use of basic decision heuristics that imperfectly exploit immediate rewards: a repetition bias and win-stay-lose-shift heuristic. These heuristics interact with uncertainty, favoring heuristic choices under higher uncertainty. These results, highlighting the rich and varied structure of reward-based choice, are a step to understanding its functional basis and dysfunction in psychopathology. |
| Abstract: | Abstract Young children's linguistic and communicative abilities are foundational for their academic achievement and overall well-being. We present the positive outcomes of a brief tablet-based intervention aimed at teaching toddlers and preschoolers new word-object and letter-sound associations. We conducted two experiments, one involving toddlers ( {\textbackslash}textasciitilde 24 months old, n = 101) and the other with preschoolers ( {\textbackslash}textasciitilde 42 months old, n = 152). Using a pre-post equivalent group design, we measured the children's improvements in language and communication skills resulting from the intervention. Our results showed that the intervention benefited toddlers' verbal communication and preschoolers' speech comprehension. Additionally, it encouraged vocalizations in preschoolers and enhanced long-term memory for the associations taught in the study for all participants. In summary, our study demonstrates that the use of a ludic tablet-based intervention for teaching new vocabulary and pre-reading skills can improve young children's linguistic and communicative abilities, which are essential for future development. |