Jean-Baptiste André. et al. (2022). Keywords in Economics and Evolutionary Biology: Twenty Five Concepts. In: From Evolutionary Biology to Economics and Back. History, Philosophy and Theory of the Life Sciences, vol 28. Springer, Cham.

Résumé :
This section exposes twenty-five key concepts in evolutionary biology and in economics. Each concept is explicated first in evolutionary biology, then in economics. Then, a short synthesis presents some differences and some commonalities.
Speech recognition in noisy environments can be challenging and requires listeners to accurately segregate a target speaker from irrelevant background noise. Stochastic figure-ground (SFG) tasks in which temporally coherent inharmonic pure-tones must be identified from a background have been used to probe the non-linguistic auditory stream segregation processes important for speech-in-noise processing. However, little is known about the relationship between performance on SFG tasks and speech-in-noise tasks nor the individual differences that may modulate such relationships. In this study, 37 younger normal-hearing adults performed an SFG task with target figure chords consisting of four, six, eight, or ten temporally coherent tones amongst a background of randomly varying tones. Stimuli were designed to be spectrally and temporally flat. An increased number of temporally coherent tones resulted in higher accuracy and faster reaction times (RTs). For ten target tones, faster RTs were associated with better scores on the Quick Speech-in-Noise task. Individual differences in working memory capacity and self-reported musicianship further modulated these relationships. Overall, results demonstrate that the SFG task could serve as an assessment of auditory stream segregation accuracy and RT that is sensitive to individual differences in cognitive and auditory abilities, even among younger normal-hearing adults.

Tarryn Balsdon, Valentin Wyart, Pascal Mamassian (2022). Robust changes in confidence efficiency during post-decision time windows. Journal of Vision ;22(14):3251.doi:10.1167/jov.22.14.3251.

Résumé :
Perceptual decisions are accompanied by feelings of confidence that reflect decision validity. Though these feelings of confidence rely on perceptual evidence, dissociations between confidence and perceptual sensitivity are common. One explanation for these dissociations is that confidence utilises ongoing processing after the completion of perceptual decision processes (Pleskac and Busemeyer, 2010, Psych Rev). Here we demonstrate causal evidence for this claim by showing robust differences in confidence efficiency depending on the duration of post-decision time windows. We measured confidence efficiency using a forced-choice design: human observers chose which of two consecutive perceptual decisions was more likely to be correct. Post-decision time pressure was manipulated (whilst leaving stimulus presentation duration constant) by forcing observers to wait to enter their response, or cueing them to respond almost immediately (leaving limited time for ongoing processing before the next trial). This manipulation had limited effects on perceptual sensitivity, but large effects on confidence efficiency. The effect on confidence efficiency depended on the level of processing of the perceptual decision. For high-level perceptual decisions (discriminating the direction of gaze of an avatar face), confidence efficiency benefitted from additional time. But for low-level perceptual decisions about the same stimuli (discriminating the relative contrast of the eyes’ irises), confidence efficiency diminished with time. Over five experiments, we demonstrate the effect of perceptual decision-level within-subjects (Exp. 1 and 2) and the effect of time pressure within-subjects (Exp. 3 and 4). In Experiment 5, we generalise these findings to biological motion stimuli. Robust differences in confidence efficiency can be generated within-subjects, independently of perceptual sensitivity, by manipulating post-decision time windows. These results suggest that confidence strongly relies on the post-decisional processing of ongoing internal representations, that quickly degrade for low-level perception.

Monica Barbir, Mireille J. Babineau, Anne-Caroline Fiévet, Anne Christophe (2022). Rapid infant learning of syntactic–semantic links. Pnas. 120 (1) e2209153119. doi:10.1073/pnas.2209153119

Résumé :
Infants start learning words at an incredible pace in their second year of life. One of the strategies they use to learn words so efficiently is to take advantage of clues hidden in grammar: ‘syntactic bootstrapping’. How infants with fledgling lexicons learn complex relationships between words and grammar is unknown. Using eye tracking, we demonstrate that 1 to 2-y-old infants can quickly learn a novel relationship between words and grammar from short videos and use it to learn new words. These results show that young language learners exploit links between language elements on the fly, suggesting that infants self-supervise learning through a network of efficient language-learning shortcuts.

Mélusine Boon-Falleur, Brigitte Dormont, Coralie Chevallier (2022). Does higher perceived risk of morbidity and mortality decrease risk-taking? R. Soc. Open Sci. 9: 220486.doi:10.1098/rsos.220486

Résumé :
Previous studies have shown that people change their behaviour in response to negative shocks such as economic downturns or natural catastrophes. Indeed, the optimal behaviour in terms of inclusive fitness often varies according to a number of parameters, such as the level of mortality risk in the environment. Beyond unprecedented restrictions in everyday life, the COVID-19 pandemic has profoundly affected people’s environment. In this study, we investigated how people form their perception of morbidity and mortality risk associated with COVID-19 and how this perception in turn affects psychological traits, such as risk-taking and patience. We analysed data from a large survey conducted during the first wave in France on 3353 nationally representative people. We found that people use public information on COVID-19 deaths in the area where they live to form their perceived morbidity and mortality risk. Using a structural model approach to lift endogeneity concerns, we found that higher perceived morbidity and mortality risk increases risk aversion. We also found that higher perceived morbidity and mortality risk leads to less patience, although this was only observed for high levels of perceived risk. Our results suggest that people adapt their behaviour to anticipated negative health shocks, namely the risk of becoming sick or dying of COVID-19.

Brian Buccola (2022). A higher-order plurality solution to Xiang's (2021) puzzle. Proceedings SALT 32: 413-419.

Résumé :
Xiang (2021) notes the following puzzle: plural wh-questions involving certain collective predicates are predicted to carry a uniqueness presupposition (Dayal 1996), yet intuitively they don’t (cf. Gentile & Schwarz 2020). She proposes that such questions have ‘higher-order readings’ (Spector 2007, 2008), and crucially that they have answers naming boolean conjunctions. I show that for the data she considers, recourse to higher-order question readings is mistaken: Xiang’s puzzle should be solved with higher-order plurality, and I provide empirical justification for this approach, mirroring for questions the recent findings for declaratives by Buccola, Kuhn & Nicolas (2021).

Guillaume Dezecache, Hugo Mercier (2022). Emotional Vigilance. T. Shackelford; L. Al-Shawaf. The Oxford Handbook of Evolution and the Emotions, Oxford University Press.

Résumé :
Although emotional displays have long been considered as mere read-outs of the affective state of agents, recent studies and modern evolutionary thinking instead suggest that they should be characterized as proper communicative signals. This implies that emotional displays have evolved to be used strategically, to serve the senders' interests. However, for these signals to be stable, they must also benefit receivers. What guarantees that emotional signals are beneficial for both emitters and observers? In this chapter, we review evidence showing that humans are equipped with mechanisms that evolved to evaluate emotional displays and their sources, so as to minimize the risk of being fooled. We called these mechanisms 'emotional vigilance,' following the 'epistemic vigilance' mechanisms used in ostensive communication. Emotional vigilance, we argue, is part of the human cognitive make-up, and we outline empirical avenues to best elucidate its features.

Tahnée Engelen, Anne Buot, Julie Grèzes, Catherine Tallon-Baudry (2023). Whose emotion is it? Perspective matters to understand brain-body interactions in emotions. NeuroImage, 119867, ISSN 1053-8119, doi:10.1016/j.neuroimage.2023.119867.

Résumé :
Feeling happy, or judging whether someone else is feeling happy are two distinct facets of emotions that nevertheless rely on similar physiological and neural activity. Differentiating between these two states, also called Self/Other distinction, is an essential aspect of empathy, but how exactly is it implemented? In non-emotional cognition, the transient neural response evoked at each heartbeat, or heartbeat evoked response (HER), indexes the self and signals Self/Other distinction. Here, using electroencephalography (n=32), we probe whether HERs’ role in Self/Other distinction extends also to emotion – a domain where brain-body interactions are particularly relevant. We asked participants to rate independently validated affective scenes, reporting either their own emotion (Self) or the emotion expressed by people in the scene (Other). During the visual cue indicating to adopt the Self or Other perspective, before the affective scene, HERs distinguished between the two conditions, in visual cortices as well as in the right frontal operculum. Physiological reactivity (facial electromyogram, skin conductance, heart rate) during affective scene co-varied as expected with valence and arousal ratings, but also with the Self- or Other- perspective adopted. Finally, HERs contributed to the subjective experience of valence in the Self condition, in addition to and independently from physiological reactivity. We thus show that HERs represent a trans-domain marker of Self/Other distinction, here specifically contributing to experienced valence. We propose that HERs represent a form of evidence related to the ‘I’ part of the judgement ‘To which extent do I feel happy’. The ‘I’ related evidence would be combined with the affective evidence collected during affective scene presentation, accounting at least partly for the difference between feeling an emotion and identifying it in someone else.

Marissa H. Evans, Shannon M. Locke, Michael S. Landy (2022). Prospective and Retrospective Cues for Sensorimotor Confidence in a Reaching Task. Journal of Vision; 22(14): 3552.doi:10.1167/jov.22.14.3552.

Résumé :
On a daily basis, humans interface with the outside world using judgments of sensorimotor confidence, constantly evaluating our actions for success. We ask, what sensory and motor-execution cues are used in making these judgements and when are they available? Prospective cues available prior to the action (e.g., knowledge of motor noise and past performance), and retrospective cues specific to the action itself (e.g., proprioceptive measurements and uncertainty) provide two timepoints at which to assess sensorimotor confidence. We investigated the inputs available at these two timepoints in a task in which participants reached toward a visual target with an unseen hand and then made a continuous judgment of confidence about the success of their reach. The confidence report was made by setting the size of a circle centered on the reach-target location, where a larger circle reflects lower confidence. Points were awarded if the confidence circle enclosed the true endpoint, with fewer points returned for larger circles. This incentivized attentive reporting and accurate reaches to maximize the score. We compared three Bayesian-inference models of sensorimotor confidence based on either prospective cues, retrospective cues, or both sources of information to maximize expected gain (i.e., an ideal observer). Each participant’s motor and proprioceptive noise were fit based on a motor-awareness task: participants reached repeatedly to a fixed target and reported the perceived endpoint. Our findings showed two distinct strategies: participants either performed as ideal observers, using both prospective and retrospective cues to make the confidence judgment, or relied solely on prospective information, ignoring retrospective cues. Thus, participants make use of retrospective cues in a motor-awareness task, but these cues are not always included in the computation of sensorimotor confidence.

Basile Garcia, Maël Lebreton, Sacha Bourgeois-Gironde et al.(2023). Experiential values are underweighted in decisions involving symbolic options. Nat Hum Behav. doi:10.1038/s41562-022-01496-3

Résumé :
Standard models of decision-making assume each option is associated with subjective value, regardless of whether this value is inferred from experience (experiential) or explicitly instructed probabilistic outcomes (symbolic). In this study, we present results that challenge the assumption of unified representation of experiential and symbolic value. Across nine experiments, we presented participants with hybrid decisions between experiential and symbolic options. Participants’ choices exhibited a pattern consistent with a systematic neglect of the experiential values. This normatively irrational decision strategy held after accounting for alternative explanations, and persisted even when it bore an economic cost. Overall, our results demonstrate that experiential and symbolic values are not symmetrically considered in hybrid decisions, suggesting they recruit different representational systems that may be assigned different priority levels in the decision process. These findings challenge the dominant models commonly used in value-based decision-making research.

Nadia Hosseinizaveh, Pascal Mamassian (2022). The effect of confidence on visual perceptual learning. Journal of Vision;22(14):3950. doi: https://doi.org/10.1167/jov.22.14.3950.

Résumé :
Visual perceptual learning can occur in the absence of external feedback provided in the environment (Sasaki et al., 2010, Nat Rev Neuro). Here, we are testing whether confidence about the validity of our perceptual decisions could be this internal mechanism that can affect perceptual learning when there is no external feedback. We asked human participants to decide about the direction of motion of a random-dot kinematogram (RDK) stimulus over five consecutive days. Every two decisions, participants reported their confidence about the accuracy of their perceptual decision using the confidence forced-choice (CFC) method. In order to investigate the effect of confidence on perceptual learning, we manipulated confidence by intertwining two conditions in which the signal-to-noise ratio is similar but the absolute evidence differs. The two conditions consisted in high- and low-density stimuli, where the number of both signal and noise dots was higher in the high than in the low-density condition. To separate the learning procedures in the two conditions, the direction of motion in the RDK stimulus was along different axes in high- vs. low-density conditions. Thresholds were estimated for %65 and %85 correct at the beginning of each day, using the method of constant stimuli (day 1) or an Accelerated Stochastic Approximation (ASA) staircase (subsequent days). In line with previous studies (Maniscalco et al., 2020, PsyArXiv), our results showed that increasing the absolute evidence while keeping the signal-to-noise ratio constant leads to overconfidence in the high-density condition. Additionally, in the low-density condition, as compared to the high-density, participants exhibited a greater improvement in both confidence efficiency and sensory threshold across days. Altogether, our results suggest that in the absence of external feedback, confidence can act as the only available feedback system, and can facilitate visual perceptual learning.

Geraldine Jeckeln, Pascal Mamassian, Alice J. O'Toole (2022). People can evaluate the correctness of their face-identification decisions using comparative confidence judgments. Journal of Vision;22(14):3341. doi:10.1167/jov.22.14.3341.

Résumé :
Confidence judgments serve as an indicator of identification accuracy in legal practices such as forensic face examination (Phillips et al., 2018). However, little research has focused on the factors that underlie these judgments. Moreover, it is not even clear whether people can evaluate the correctness of their face-identification decisions reliably through confidence reports. Previous studies show that confidence is a good indicator of accuracy when it is based on the strength of the sensory stimulus and when it is assessed with minimal bias (Mamassian, 2016; Wixted & Wells, 2017). Here, we implemented comparative judgments to measure confidence more directly and eliminate the risk of response bias imposed by the commonly used confidence scales (Mamassian, 2020; Phillips et al., 2018). Specifically, we tested participants (N = 58) on a confidence forced-choice task embedded in a face-identification test. On each face-identification trial, participants viewed three face images (two same-identity images, one different-identity image). The task was to select the odd-one-out. Upon completion of two face-identification trials (trial pair), participants compared the two decisions and selected the trial on which they felt more confident. To measure how task difficulty informs confidence decisions, we extracted item-difficulty estimates from an Item Response Theory model fitted to data collected separately. The difference in difficulty between the items in a trial pair predicted the proportion of higher-confidence judgments allocated to the easier item of the pair (R2 = 0.4924, F(1,50)= 50.48, p < .001). Performance was significantly more accurate on higher-confidence trials (M= 0.8853, SE= 0.0138), in comparison to lower-confidence trials (M=0.7924, SE=0.0176), (t(53) = 8.7689, p < .001, 95% CI:[ 0.0717, 0.1142], Cohen’s d=.7994). These findings show that people monitor task difficulty to evaluate the correctness of their face-identification decisions and comparative confidence judgments are good indicators of face-identification accuracy.

Ivan Lazarevich, Iilya Prokin, Boris Gutkin, Victor Kazantsev (2023). Spikebench: An open benchmark for spike train time-series classification. PLoS Comput Biol. 19(1): e1010792.

Résumé :
Modern well-performing approaches to neural decoding are based on machine learning models such as decision tree ensembles and deep neural networks. The wide range of algorithms that can be utilized to learn from neural spike trains, which are essentially time-series data, results in the need for diverse and challenging benchmarks for neural decoding, similar to the ones in the fields of computer vision and natural language processing. In this work, we propose a spike train classification benchmark, based on open-access neural activity datasets and consisting of several learning tasks such as stimulus type classification, animal’s behavioral state prediction, and neuron type identification. We demonstrate that an approach based on hand-crafted time-series feature engineering establishes a strong baseline performing on par with state-of-the-art deep learning-based models for neural decoding. We release the code allowing to reproduce the reported results.

V. Lenglin, S. Wong, C. O’Callaghan, S. Erzinçlioğlu, M. Hornberger, T. Lebouvier, O. Piguet, S. Bourgeois-Gironde, M. Bertoux (2022). Zero the hero: evidence for involvement of the ventromedial prefrontal cortex in affective bias for free items. Cortex, ISSN 0010-9452. doi:10.1016/j.cortex.2022.12.009.

Résumé :
Recent evidence from psycho-economics shows that when the price of an item decreases to the extent that it becomes available for free, one can observe a remarkable increase of subjective utility toward this item. This phenomenon, which is not observed for any other price but zero, has been termed the zero-price effect (ZPE). The ZPE is attributed to an affective heuristic where the positive affect elicited by the free status of an item provides a mental shortcut biasing choice towards that item. Given that the ZPE relies on affective processing, a key role of the ventromedial prefrontal cortex (vmPFC) has been proposed, yet neuroscientific studies of the ZPE remain scarce. This study aimed to explore the role of the vmPFC in the ZPE using a novel, within-subject assessment in participants with either an acquired (lesion patients) or degenerative (behavioural-variant frontotemporal dementia patients) lesion of the vmPFC, and age-matched healthy controls. All participants were asked to make a series of choices between pairs of items that varied in price. One choice trial involved an equal decrease of both item prices, such that one of the items was priced zero. In contrast to controls, both vmPFC-lesion and behavioural-variant frontotemporal dementia patients showed marked reductions in zero-related changes of preference in pairs of gift-cards, but not for pairs of food items. Our findings suggest that affective evaluations driving the ZPE are altered in patients with focal or degenerative damage to the vmPFC. This supports the notion of a key role of the vmPFC in the ZPE and, more generally, the importance of this region in value-based affective decision-making. Our findings also highlight the potential utility of affective heuristic tasks in future clinical assessments.

Shannon M. Locke, Alexander Goettker, Karl R. Gegenfurtner, Pascal Mamassian (2022). Sensorimotor confidence for tracking eye movements. Journal of Vision;22(14):3500. doi:10.1167/jov.22.14.3500.

Résumé :
Accurate and precise eye movements are important for visual perception. Yet, both saccades and smooth-pursuit are affected by sensory and motor noise, and are constrained by limited processing time. Can observers report the degree of accuracy in their eye movements, despite typically being unaware of the eye’s constant movement? To investigate this question, we measured sensorimotor confidence for tracking of unpredictably moving targets that elicited both saccades and smooth-pursuit behaviour. We define sensorimotor confidence as the subjective evaluation of task performance that should take into account sensory and motor uncertainty as well as the sensorimotor goal (e.g., maximise tracking accuracy). We asked human observers to track the centre of a noisy dot cloud with their eyes as it moved horizontally. The trajectory followed a sum of sinusoids (average speed: 9 deg/s). There were 20 unique trajectories, repeated 12 times each, half with direction reversed, presented in a randomised order. After 6 seconds of tracking, observers reported if they thought their tracking performance was better or worse than their estimated average performance in the task. From these sensorimotor confidence judgments, we computed their metacognitive sensitivity, the ability to classify objectively better from objectively worse performance, using an ROC-style analysis (Locke et al., 2020, Cognition). Metacognitive sensitivity was significantly above chance-level (area-under-the-curve of 0.50) for the group, however only marginally so (mean and SEM: 0.56 ± 0.02, n = 7). Investigating the individual repeated trajectories by performing a median-split of the objectively better versus worse repeats, all observers were on average more likely to report “better” for the better half of repeats. Together these results suggest humans have marginal metacognitive sensitivity for tracking eye movements. This limited access to sensorimotor uncertainty may be the cost for humans to make fast and accurate eye movements.

Estefania Lozaa, Frédérique Amsellem, Tiziana Zalla, Ariane Cartigny, Marion Leboyer, Richard Delorme, Franck Ramus, Baudouin Forgeot d′Arc (2023). A mind-reading puzzle: Autistic people are more efficient at a theory-of-mind task. Research in Autism Spectrum Disorders. Volume 101, 102105

Résumé :
Theory of Mind (ToM) is essential to adapt in social situations; however, a ToM deficit might be involved in autism. To better understand how ToM reasoning affects problem solving in autistic and non-autistic individuals, we compared autistic and non-autistic children and adults in a series of problems presented in social and non-social framings, using an adapted version of a classical referential communication task. In the social framing, participants were asked to anticipate the behavior of an agent who might ignore some components of the scene. In the non-social framing, the task required participants to consider and ignore similar features of the scene, but an agent was not involved. Simply framing the task as a social one increased the difficulty, particularly for non-autistic participants. Interestingly, the framing had less of an impact on autistic participants, who showed better performance in the social task relative to non-autistics and maintained similar performance across framings. We propose that autistic participants might have translated the social instructions into a general rule that proved more efficient in this situation. Our findings suggest a critical distinction between ToM understanding and the continuous use of a ToM strategy in repeated situations.

Pascal Mamassian (2022). Reverse motion from reversed time perception?. Journal of Vision ;22(14):4095. doi:10.1167/jov.22.14.4095.

Résumé :

Apparent motion is the experience of motion from the quick successive stimulation of nearby spatial locations. We report here a phenomenon of reverse apparent motion from three frames that is consistent with a re-ordering of successive frames. In contrast to other reverse motion reports in the literature (e.g. Shioiri & Cavanagh, 1990, Vision Research), the present reversal is not obtained by manipulating the moving stimulus itself. Instead, the same physical stimulus is perceived moving forward or in reverse direction depending on what is presented just before. Observers had to decide on the direction of rotation of a test movie. The test movie consisted of 3 frames of 4 dots placed at the corners of a virtual square centered on the fixation point. On each frame, the dots rotated 30 degrees, either clockwise or counter-clockwise randomly across trials. The inter-stimulus interval (ISI) between two successive frames (1-2 or 2-3) was fixed to 100ms, and the other ISI varied from trial to trial from 0 to 200ms. Before the test movie, 4 frames of 4 dots were presented, either at 4 random locations (baseline condition), or at the location of the dots in one frame of the test movie (adapting condition). The baseline condition confirmed that without adaptation, the physical movie was correctly perceived in its forward direction. When the second frame of the movie was adapted, perceived motion was consistently reversed for short ISIs, but importantly forward motion was recovered for long ISIs. When either the first or last frame was adapted, forward motion was perceived. The results are discussed in relationship to different models, including a confusion of the order of successive frames, a change of the impulse response function, and a late interpretation of past events at the end of a temporal window.

Thomas Schaffhauser, Alain De Cheveigné, Yves Boubenec, Pascal Mamassian (2022). EEG evoked activity suggests amodal evidence integration in multisensory decision-making. Journal of Vision; 22(14):3963. doi:10.1167/jov.22.14.3963.

Résumé :
Recent works in neuroimaging have revealed neural signatures of evidence integration (O’Connell et al., 2012, Nat Neuro; Philiastides et al., 2014, J Neuro) that reflect the ramping activity of neurons in the parietal cortex. While these experiments focused on unisensory visual and auditory perceptual decision-making, it is unclear to what extent the neural correlates of multisensory evidence integration are shared with their unisensory counterparts. To address this issue, we designed a change detection paradigm in which twenty-one participants monitored a continuous stream of visual random dot motion and auditory tone clouds. The random dot motion was displayed within a circular aperture and consisted of 200 small dots repositioned every 50 ms. The tone clouds consisted of 10 simultaneous 50 ms pure tones drawn from a range of 6 octaves (220 to 14,080 Hz) with a resolution of 12 semitones per octave. In this continuous bimodal stream, participants had to detect unisensory changes (a change from incoherent noise to a coherent pattern of upward moving dots or rising tone sequences) or bimodal changes (simultaneous auditory and visual changes in coherence) while continuous EEG was acquired via 64 scalp electrodes. EEG activity was denoised with spatial filtering techniques to isolate components that capture neural activity most reproducibly evoked by stimulus change onset (de Cheveigné & Simon, 2008, J Neuro Methods). EEG evoked activity could be discriminated between visual and auditory target stimuli highlighting separable encoding of visual and auditory coherence changes. Further analyses revealed a component rising before participants response that echoes evidence accumulation and appeared to be common for both unisensory (visual, auditory) and redundant audio-visual changes. These results point to a single amodal accumulator that integrates evidence coming from each sensory modality in isolation or a combined bimodal signal.

Richard Schweitzer, Tamara Watson, Tarryn Balsdon, Martin Rolfs (2022). The sources of peri-saccadic mislocalization: Evidence from the perception of intra-saccadic motion streaks. Journal of Vision; 22(14):3897. doi:10.1167/jov.22.14.3897.

Résumé :
To localize objects in egocentric space, the visual system needs to combine two sources of information: (1) a retinal input that arrives with neural latencies that depend on stimulus parameters and (2) a rapidly changing estimate of gaze direction. To scrutinize the temporal synchronization and fidelity of these sources, we asked observers to report trajectories of objects fleetingly presented while the eyes are moving. Using a high-speed projection system, we probed human observers’ ability to localize and report the appearance of motion streaks arising from briefly presented, strictly intra-saccadic visual targets, moving at high velocities along an unpredictable trajectory on the screen. Across four experiments we found that such intra-saccadic motion streaks were readily perceived in world-centered coordinates but with characteristic deviations: Phenomenological reports of motion trajectories were systematically skewed in the direction of the saccade, but clearly different from the object’s trajectory in retinal coordinates. These response patterns remained largely unaffected by varying visual-field location, background luminance and structure, and even additional large-field background motion injected during saccades. Perceived motion trajectories did, however, clearly depend on the inducing target’s Weber contrast and timing during the saccade. To explain these results, we implemented a model in which the perceived motion trajectory is a result of adding the target’s retinal trajectory to a saccade-like eye position signal. Generally, observer’s reports were well approximated when the eye position signal was early-onset and damped in time, in agreement with classic models of peri-saccadic mislocalization. Inspired by recordings from simple cells in V1, we extended these models by simulating the temporal response characteristics of early vision. These simulations suggested that sluggish visual responses cause the retinotopic position signal to extend in time. Counterintuitively, a dampened representation of eye position may in fact be optimal to reduce mislocalization error when dealing with variable visual latencies.

Jonathan Vacher, Ruben Coen-Cagli, Pascal Mamassian (2022). Unifying Different Psychometric Methods : Theory and Experiment. Journal of Vision;22(14):3879. doi:10.1167/jov.22.14.3879.

Résumé :
To estimate the sensitivity to discriminate two visual stimuli, the two-alternative forced choice (2AFC) paradigm has become a favorite method. The psychometric function that links the physical stimuli to discrimination performance can then be modeled using signal detection theory (SDT). Recent efforts to combine SDT with Bayesian probabilities have linked thresholds and biases to hypothesized prior knowledge and optimal encoding/decoding. When supra-thresholds are considered, the maximum likelihood difference scaling (MLDS) paradigm is a preferred method to estimate the perceptual scale that links a physical property to a psychological dimension. This latter method relies on the comparison of perceived differences between pairs of stimuli. Here, we are interested in modeling the MLDS paradigm with the Bayesian framework. This allows us to compare sensitivity measurements obtained from MLDS and 2AFC methods. We first show how the perceptual scale can be derived from SDT and Bayesian probabilities, thereby providing a unifying theoretical framework. In particular, we show that this theory predicts that the slope of the psychometric function at the point of subjective equality is proportional to the derivative of the perceptual scale. In other words, the perceptual scale is the scale that uniformizes the sensitivity. Next, we demonstrate the consistency of both experimental techniques and their compatibility with information theory (optimal coding) using human participants’ data. More precisely, we illustrate our theoretical results with two behavioral experiments: (i) new measurements of the perceptual scale of orientation and the sensitivity to discriminate nearby orientations, and (ii) previous measurements of the perceptual scale of interpolation between pairs of textures. Our results are important for future developments in psychophysics, both theoretically and experimentally. In particular, they support the use of the MLDS technique as a possible alternative to 2AFC for measuring psychophysical sensitivities.

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