2AFC Task Research Articles

On letter-specific crowding and reading: Evidence from ERPs

We compared processing of letter and symbol stimuli presented briefly in the right or left visual field, and either in isolation or surrounded by two flanking characters of the same category. The flankers could be arranged horizontally or vertically. Participants performed a two-alternative forced choice (2AFC) task with the isolated character or the central character in flanked displays as target. Alternatives in the 2AFC task were characters from the same category as the target that were not present in the display. We recorded EEG in order to investigate the timing of crowding effects (isolated vs. flanked conditions) and the hypothesized differential impact of crowding on letters and symbols. Behavioral results showed no significant difference between isolated letters and symbols, but significantly higher accuracy to flanked letters compared with flanked symbols – and the effect of stimulus type was significantly greater with horizontally aligned stimuli. Likewise, amplitude of the N170 and a following negativity (identified here as the N250) did not differ significantly when comparing isolated letters and symbols but did differ for flanked stimuli. Flanked letters showed significantly greater N170 and N250 amplitudes compared with flanked symbols. N170 and N250 amplitudes were also significantly greater for flanked vs. isolated letters whereas symbols showed a significant difference in the opposite direction for the N250. We conclude that the processing of compact strings of letters is optimized for skilled reading via changes in the mapping of visual features onto letter identities in multi-letter arrays in order to reduce the interfering effects of excessive crowding.

Explicit Instructions Do Not Enhance Auditory Statistical Learning in Children With Developmental Language Disorder: Evidence From Event-Related Potentials.

A current issue in psycholinguistic research is whether the language difficulties exhibited by children with developmental language disorder [DLD, previously labeled specific language impairment (SLI)] are due to deficits in their abilities to pick up patterns in the sensory environment, an ability known as statistical learning (SL), and the extent to which explicit learning mechanisms can be used to compensate for those deficits. Studies designed to test the compensatory role of explicit learning mechanisms in children with DLD are, however, scarce, and the few conducted so far have led to inconsistent results. This work aimed to provide new insights into the role that explicit learning mechanisms might play on implicit learning deficits in children with DLD by resorting to a new approach. This approach involved not only the collection of event-related potentials (ERPs), while preschool children with DLD [relative to typical language developmental (TLD) controls] were exposed to a continuous auditory stream made of the repetition of three-syllable nonsense words but, importantly, the collection of ERPs when the same children performed analogous versions of the same auditory SL task first under incidental (implicit) and afterward under intentional (explicit) conditions. In each of these tasks, the level of predictability of the three-syllable nonsense words embedded in the speech streams was also manipulated (high vs. low) to mimic natural languages closely. At the end of both tasks’ exposure phase, children performed a two-alternative forced-choice (2-AFC) task from which behavioral evidence of SL was obtained. Results from the 2-AFC tasks failed to show reliable signs of SL in both groups of children. The ERPs data showed, however, significant modulations in the N100 and N400 components, taken as neural signatures of word segmentation in the brain, even though a detailed analysis of the neural responses revealed that only children from the TLD group seem to have taken advantage of the previous knowledge to enhance SL functioning. These results suggest that children with DLD showed deficits both in implicit and explicit learning mechanisms, casting doubts on the efficiency of the interventions relying on explicit instructions to help children with DLD to overcome their language difficulties.

How to test blindsight without light scatter artefacts?

light scatter artefacts are a methodological problem in testing residual visual capacities (RVCs), for instance blindsight, in patients with homonymous visual field defects (HVFDs). The term light scatter artefact describes the phenomenon that light from targets directed towards the HVFD can stray into the sighted visual field. This might enable an observer to respond correctly to information directed at her blind field despite the fact that she is unable to process that information in the blind field itself. In this manuscript, we present a review of the relevance of light scatter in visual neuroscience, discuss factors that influence the impact of light scatter and evaluate means to test for light scatter artefacts. Furthermore, we present findings from an empirical study that was aimed at developing tests for RVCs that are free of light scatter artefacts. Previous studies on light scatter only used small sample sizes and equipment that is no longer in use. Hence, their results cannot be generalized to future experiments making it necessary to run laborious light scatter tests for every new study on RVCs. To avoid this, we hereby start a pool of stimuli and paradigms which demonstrably do not elicit light scatter artefacts. To this end, we investigated 21 healthy young participants in three frequently used RVC-paradigms: (1) temporal 2AFC task, (2) movement direction discrimination, and (3) redundant target paradigm. For each paradigm, we applied the blind-spot method. But first, we had to establish that our testing paradigm was sufficiently sensitive to detect light scatter artefacts. For this, we used conditions that are known to produce strong light scatter and a paradigm that is very sensitive to such effects. Specifically, we presented white targets on a black background in a dark room. The stimuli were presented to observers’ blind spot. To check for light scatter artefacts, we used a target-detection task in a temporal 2AFC format. We obtained clear light scatter artefacts. Participants produced reliably above-chance detection performance under these conditions. The other two luminance conditions, measured in an illuminated room, did not produce light scatter artefacts. Accuracy in the temporal 2AFC task was at chance level for white targets on a grey background at the blind-spot position. Additionally, black targets on a grey background avoided light scatter artefacts in all three RVC-paradigms. In future, researchers can apply these stimulus and illumination conditions when using one of the three above paradigms in their studies. Using these conditions, they will be able to avoid light scatter artefacts without having to perform their own blind-spot tests.

Perceptual Learning of Altered Vowel Space Improves Identification of Vowels Produced by Individuals With Dysarthria Secondary to Amyotrophic Lateral Sclerosis.

This study examines the efficacy of perceptual training for improving typical listeners' identification of vowels produced by individuals with dysarthria. We examined whether training on a subset of vowels can generalize to (a) untrained vowels and (b) other speakers with similar overall intelligibility. Sixty naive listeners completed a pretest/posttest perceptual learning task. In the pretraining test and posttraining test, participants identified nine American English monophthongs produced by two speakers with dysarthria secondary to amyotrophic lateral sclerosis (ALS). In the 20-min training task, a two-alternative forced choice (2AFC) task with feedback trained listeners on a subset of the vowels and speakers presented in the pretraining test. Vowel identification accuracy improved overall as a function of training. However, patterns of generalization between speakers and vowel types were not symmetric. Specifically, listeners generalized training from front vowels to back vowels but not vice versa. Likewise, listeners generalized from one speaker to another but not in the opposite direction. Examination of confusion matrices for the pretraining and posttraining revealed complex patterns of vowel-specific improvement. This study demonstrates that listeners benefit from a very simple training paradigm targeting vowels. Additionally, error patterns revealed that vowels are both resistant to and responsive to perceptual learning. Implications for future research and clinical training paradigms are discussed.

Enumeration takes time: Accuracy improves even after stimuli disappear

Numerical cognition is widespread among animal species and present from birth in humans. Laboratory studies show that longer stimulus duration improves numerical discrimination accuracy (Inglis & Gilmore, 2013; Wood & Spelke, 2005). Inglis and Gilmore (2013) suggested that longer durations allow subjects to resample the stimulus image multiple times, resulting in a more accurate final estimate. The current study tested this “multiple sampling” model alongside two competing models – “serial foveal accumulator” (Cheyette & Piantadosi, 2019) and “longer processing time” – to determine how stimulus duration relates to accuracy. Adult subjects completed a fully within-subject, 2AFC task in which they judged which of two arrays had more dots; accuracy was the dependent measure. Experiment 1 revealed higher accuracy in the 500 ms stimulus duration condition compared to the 100 ms condition, replicating previous results. Experiments 2 and 4 extended this finding. When stimulus duration was held constant at 100 ms, adding a 400 ms delay between stimulus offset and mask onset improved accuracy. Accuracy was similar in the 500 ms stimulus duration condition (E1) and the 100 ms duration + 400 ms mask delay conditions (E2 and E4), indicating that post-stimulus processing time improves accuracy, rather than stimulus duration per se. This contrasts with both the multiple sampling model and the serial foveal model, although we cannot exclude the possibility that sampling continues in iconic memory. Numerosity was a significant factor in all four experiments, suggesting a serial component in the enumeration process. These findings shed light on the cognitive processes underlying nonverbal number representation in humans.

Measuring Aesthetic Preferences of Neural Style Transfer: More Precision With the Two-Alternative-Forced-Choice Task

The present work compares the two-alternative forced choice (2AFC) task to rating scales for measuring aesthetic perception of neural style transfer-generated images and investigates whether and to what extent the 2AFC task extracts clearer and more differentiated patterns of aesthetic preferences. To this aim, 8250 pairwise comparisons of 75 neural style transfer-generated images, varied in five parameter configurations, were measured by the 2AFC task and compared with rating scales. Statistical and qualitative results demonstrated higher precision of the 2AFC task over rating scales in detecting three different aesthetic preference patterns: (a) convergence (number of iterations), (b) an inverted U-shape (learning rate), and (c) a double peak (content-style ratio). Important for practitioners, finding such aesthetically optimal parameter configurations with the 2AFC task enables the reproducibility of aesthetic outcomes by the neural style transfer algorithm, which saves time and computational cost, and yields new insights about parameter-dependent aesthetic preferences.

Changes in visual speed perception induced by anticipatory smooth eye movements.

Expectations about forthcoming visual motion shaped by observers' experiences are known to induce anticipatory smooth eye movements (ASEMs) and changes in visual perception. Previous studies have demonstrated discrete effects of expectations on the control of ASEM and perception. However, the tasks designed in those studies were not able to segregate the effects of expectations and execution of ASEM itself on perception. In the present study, we attempted to directly examine the effect of ASEM itself on visual speed perception with a two-alternative forced-choice (2AFC) task, in which observers were asked to track a pair of sequentially presented visual motion stimuli with their eyes and to judge whether the second stimulus (test stimulus) was faster or slower than the first (reference stimulus). Our results showed that observers' visual speed perception, quantified by a psychometric function, shifted according to ASEM velocity. This was the case even though there was no difference in the steady-state eye velocity. Further analyses revealed that the observers' perceptual decisions could be explained by a difference in the magnitude of retinal slip velocity in the initial phase of ocular tracking when the reference and test stimuli were presented, rather than in the steady-state phase. Our results provide psychophysical evidence of the importance of initial ocular tracking in visual speed perception and the strong impact of ASEM.NEW & NOTEWORTHY We provide psychophysical evidence that the execution of anticipatory smooth eye movement (ASEM) leads to underestimation of visual speed perception, that is, observers perceive the object motion velocity as slower than when ASEM is not induced, even though the performance of subsequent ocular tracking is comparable. Moreover, our results showed that such perceptual decisions regarding object motion velocity were derived from the ASEM-induced decrease in retinal slip velocity during the initial phase of ocular tracking.

People can identify the likely owner of heartbeats by looking at individuals’ faces

For more than a century it has been proposed that visceral and vasomotor changes inside the body influence and reflect our experience of the world. For instance, cardiac rhythms (heartbeats and consequent heart rate) reflect psychophysiological processes that underlie our cognition and affective experience. Yet, considering that we usually infer what others do and feel through vision, whether people can identify the most likely owner of a given bodily rhythm by looking at someone's face remains unknown. To address this, we developed a novel two-alternative forced-choice task in which 120 participants watched videos showing two people side by side and visual feedback from one of the individuals' heartbeats in the centre. Participants' task was to select the owner of the depicted heartbeats. Across five experiments, one replication, and supplementary analyses, the results show that: i) humans can judge the most likely owner of a given sequence of heartbeats significantly above chance levels, ii) that performance in such a task decreases when the visual properties of the faces are altered (inverted, masked, static), and iii) that the difference between the heart rates of the individuals portrayed in our 2AFC task seems to contribute to participants' responses. While we did not disambiguate the type of information used by the participants (e.g., knowledge about appearance and health, visual cues from heartbeats), the current work represents the first step to investigate the possible ability to infer or perceive others' cardiac rhythms. Overall, our novel observations and easily adaptable paradigm may generate hypotheses worth examining in the study of human and social cognition.

Spiking Recurrent Neural Networks Represent Task-Relevant Neural Sequences in Rule-Dependent Computation.

Prefrontal cortical neurons play essential roles in performing rule-dependent tasks and working memory-based decision making. Motivated by PFG recordings of task-performing mice, we developed an excitatory-inhibitory spiking recurrent neural network (SRNN) to perform a rule-dependent two-alternative forced choice (2AFC) task. We imposed several important biological constraints onto the SRNN, and adapted spike frequency adaptation (SFA) and SuperSpike gradient methods to train the SRNN efficiently. The trained SRNN produced emergent rule-specific tunings in single-unit representations, showing rule-dependent population dynamics that resembled experimentally observed data. Under varying test conditions, we manipulated the SRNN parameters or configuration in computer simulations, and we investigated the impacts of rule-coding error, delay duration, recurrent weight connectivity and sparsity, and excitation/inhibition (E/I) balance on both task performance and neural representations. Overall, our modeling study provides a computational framework to understand neuronal representations at a fine timescale during working memory and cognitive control, and provides new experimentally testable hypotheses in future experiments.

Él Code-Switches More Than tú y yo: New Data for the Subject Pronoun-Verb Switch Constraint

In early studies, code-switches between a subject pronoun and a finite verb were considered highly dispreferred or even impossible. However, naturalistic data from several language pairs has since highlighted that such switches are possible, although their grammaticality is constrained by the typology of the pronouns involved. In this study, we test the switching constraints postulated for subject pronouns-verbs among P’urhepecha-Spanish bilinguals (n = 12) from Michoacán, western Mexico. Using a two-alternative forced-choice acceptability judgement task (2AFC), we found that, contrary to expectations, switches between a third person singular pronoun and a verb were considered the most acceptable, followed by the coordinated ‘you and I’ second person, then the first person singular. The same order was found for both switch directions, despite third-person pronouns in P’urhepecha having a stronger typological profile. Building on the results of previous studies, we suggest that the lack of preference for a single switch direction is evidence for language-specific code-switching patterns, as well as possible differences in productive vs. receptive language. Additionally, we highlight the probative value of judgement data, particularly those emerging from 2AFC tasks, as a means of expanding our understanding of grammaticality in code-switching.

Emotion-modulated Recall: Congruency Effects of Nonverbal Facial and Vocal Cues on Semantic Recall

The current study had two main goals: First, to replicate the ‘bimodal integration’ effect (i.e. the automatic integration of crossmodal stimuli, namely facial emotions and emotional prosody); and second, to investigate whether this phenomenon facilitates or impairs the intake and retention of unattended verbal content. The study borrowed from previous bimodal integration designs and included a two-alternative forced-choice (2AFC) task, where subjects were instructed to identify the emotion of a face (as either ‘angry’ or ‘happy’) while ignoring a concurrently presented sentence (spoken in an angry, happy, or neutral prosody), after which a surprise recall was administered to investigate effects on semantic content retention. While bimodal integration effects were replicated (i.e. faster and more accurate emotion identification under congruent conditions), congruency effects were not found for semantic recall. Overall, semantic recall was better for trials with emotional (vs. neutral) faces, and worse in trials with happy (vs. angry or neutral) prosody. Taken together, our findings suggest that when individuals focus their attention on evaluation of facial expressions, they implicitly integrate nonverbal emotional vocal cues (i.e. hedonic valence or emotional tone of accompanying sentences), and devote less attention to their semantic content. While the impairing effect of happy prosody on recall may indicate an emotional interference effect, more research is required to uncover potential prosody-specific effects. All supplemental online materials can be found on OSF (https://osf.io/am9p2/).

The dynamics of decision-making and action during active sampling

Embodied Cognition Theories (ECTs) of decision-making propose that the decision process pervades the execution of choice actions and manifests itself in these actions. Decision-making scenarios where actions not only express the choice but also help sample information can provide a valuable, ecologically relevant model for this framework. We present a study to address this paradigmatic situation in humans. Subjects categorized (2AFC task) a central object image, blurred to different extents, by moving a cursor toward the left or right of the display. Upward cursor movements reduced the image blur and could be used to sample information. Thus, actions for decision and actions for sampling were orthogonal to each other. We analyzed response trajectories to test whether information-sampling movements co-occurred with the ongoing decision process. Trajectories were bimodally distributed, with one kind being direct towards one response option (non-sampling), and the other kind containing an initial upward component before veering off towards an option (sampling). This implies that there was an initial decision at the early stage of a trial, whether to sample information or not. Importantly, in sampling trials trajectories were not purely upward, but rather had a significant horizontal deviation early on. This result suggests that movements to sample information exhibit an online interaction with the decision process, therefore supporting the prediction of the ECTs under ecologically relevant constrains.

A novel Android app to evaluate and enhance auditory and tactile temporal thresholds.

With this work, we introduce a novel Android app designed to monitor and enhance auditory and tactile temporal sensitivity. To assess the app's reliability, we tested its technical performance evaluating stimuli production's accuracy (i.e., onset, offset, and duration of stimulation). To validate the app with participants we generated temporal intervals, using either sounds or vibratory stimuli, by implementing two versions of a Two-Alternative Forced-Choice (2AFC) task. Auditory and tactile temporal sensitivity of 12 participants was evaluated using this procedure. To investigate whether temporal abilities could be enhanced using the app, participants were then divided into two groups: one group was trained for four days on the auditory temporal task, while the other was trained for four days on the tactile temporal task. Results suggest that the app can i) effectively measure auditory and tactile temporal thresholds and ii) be used to enhance temporal abilities through perceptual learning. The accessibility of the experimental protocols, combined with our findings, fosters the app's involvement in rehabilitation programs, for example, with a specific focus on sensory disabilities that are associated with temporal deficits (e.g., deafness and Parkinson).Clinical Relevance- The current work introduces a novel app that can be used to monitor and improve temporal abilities, in both the auditory and the tactile modalities.

Unmasking the effects of orthography, semantics, and phonology on 2AFC visual word perceptual identification

ABSTRACT In the two-alternative forced-choice (2AFC) task, the target stimulus is presented very briefly, and participants must choose which of two options was the presented target. Some past research has assumed that the 2AFC task isolates orthographic effects, despite orthographic, semantic, and phonological differences between the options. If so, performance should not differ between word/nonword pairs and British/American word pairs, the latter of which only differ orthographically. In Experiment 1, accuracy and sensitivity were higher during word/nonword trials than British/American trials when participants did not guess, demonstrating that phonological/semantic processing contributes to performance. Experiment 2 showed that target visibility did not interact with pair type on RT, which suggests phonological/semantic processing did not feed back to orthographic encoding in this task. This study demonstrates the influence of phonological/semantic processing on word perceptual identification, and shows that using British/American word pairs provides a method to isolate orthography in the 2AFC task.

What we’ve been missing about what we’ve been missing: Above-chance sensitivity to inattentional blindness stimuli

Inattentional blindness—the failure to report clearly visible stimuli when attention is otherwise engaged—is among the most striking and well-known phenomena in psychology. But does inattention really render subjects “blind,” or do they see more than their reports suggest? Standardly, IB studies simply ask subjects whether they noticed anything unusual on the critical trial, treating anyone who says “no” as having failed to perceive the stimulus. Yet this yes/no measure is susceptible to bias. Subjects might respond “no” because they were under-confident whether they saw anything (or whether what they saw counted as unusual), because they doubted that they could identify it, etc. Here, we address this problem by modifying the classic IB paradigm to allow derivation of signal-detection measures of sensitivity and bias. Subjects’ primary task was to report which arm of a briefly presented cross was longer. In Experiments 1 and 2, the last trial included an unexpected stimulus. However, after the traditional yes/no question, subjects also answered a two-alternative forced-choice (2AFC) question, e.g., “Was the stimulus on the left or right?” or a forced-response question, e.g., “Was the stimulus red or blue?”. We found that subjects who reported not noticing the IB stimulus could nevertheless discriminate its features (e.g., color, location) well above-chance. In Experiment 3, only two-thirds of subjects were shown an unusual stimulus, providing a false-alarm rate with which to derive detection-theoretic statistics. Subjects also provided confidence ratings for their reports, allowing us to construct confidence-based ROC curves. As predicted, yes/no reports were conservatively biased (i.e., subjects tended to say “no”). Sensitivity did not differ significantly across yes/no and 2AFC tasks, suggesting that standard estimates of IB may be inflated by such biases. These results are consistent with a rarely discussed account of IB: Inattention does not abolish awareness; rather, it degrades it.

The orientation-difference cue in figure-ground separation: border ownership and timing

Figure-ground separation, a crucial component of visual processing, can be driven by differences in contrast, orientation, and other local cues. We previously showed (VSS 2020) that the orientation cue has distinctive characteristics: figure-ground separation depends not only on the magnitude of the orientation difference, but also on whether the oriented component is present in the figure vs. the ground. Here we show that this dependence is invariant with respect to convexity vs. concavity of the figure, and determine how it evolves over time. In a 2-AFC task, subjects (N=3) distinguished a target image containing five randomly-positioned figures rendered by one synthetic texture superimposed on a background defined by a second synthetic texture, from a non-target image consisting of a uniform texture whose image statistics matched the spatial average of the target’s statistics. Target and non-target images consisted of 64 x 64 arrays of 10-min black and white checks, and the figures covered 25% of the target’s area. Texture construction enabled control of the spatial frequency content of figure and ground in one or two orientations. For figures consisting of circular discs, figure-ground separation was facilitated when the figure texture was oriented, compared to when the ground was oriented. This difference was linked to the degree of anisotropy, as determined from the textures’ spectra (r=0.82, p<0.001). When figure boundaries were changed from convex to concave, results were similar, indicating that figure content and border ownership, but not border shape, determined performance. In preliminary results (N=1), we find that this asymmetry develops slowly; it is largely absent for a presentation time of 125 ms but close to maximal at 250 ms. In sum, figure-ground separation uses orientation differences in a way that depends on figure-ground assignment, suggesting a recurrent process that evolves over time.

A passive and objective measure of recognition memory in Alzheimer's disease using Fastball memory assessment.

Earlier diagnosis of Alzheimer's disease requires biomarkers sensitive to associated structural and functional changes. While considerable progress has been made in the development of structural biomarkers, functional biomarkers of early cognitive change, unconfounded by effort, practice and level of education, are still needed. We present Fastball, a new EEG method for the passive and objective measurement of recognition memory, that requires no behavioural memory response or comprehension of the task . Younger adults, older adults and Alzheimer's disease patients (n = 20 per group) completed the Fastball task, lasting just under 3 min. Participants passively viewed rapidly presented images and EEG assessed their automatic ability to differentiate between images based on previous exposure, i.e. old/new. Participants were not instructed to attend to previously seen images and provided no behavioural response. Following the Fastball task, participants completed a two-alternative forced choice (2AFC) task to measure their explicit behavioural recognition of previously seen stimuli. Fastball EEG detected significantly impaired recognition memory in Alzheimer's disease compared to healthy older adults (P < 0.001, Cohen's d = 1.52), whereas behavioural recognition was not significantly different between Alzheimer's disease and healthy older adults. Alzheimer's disease patients could be discriminated with high accuracy from healthy older adult controls using the Fastball measure of recognition memory (AUC = 0.86, P < 0.001), whereas discrimination performance was poor using behavioural 2AFC accuracy (AUC = 0.63, P = 0.148). There were no significant effects of healthy ageing, with older and younger adult controls performing equivalently in both the Fastball task and behavioural 2AFC task. Early diagnosis of Alzheimer's disease offers potential for early treatment when quality of life and independence can be retained through disease modification and cognitive enhancement. Fastball provides an alternative way of testing recognition responses that holds promise as a functional marker of disease pathology in stages where behavioural performance deficits are not yet evident. It is passive, non-invasive, quick to administer and uses cheap, scalable EEG technology. Fastball provides a new powerful method for the assessment of cognition in dementia and opens a new door in the development of early diagnosis tools.

Preference for Facial Symmetry Depends on Study Design

Facial symmetry is purportedly attractive, though methods for measuring preference for facial symmetry vary between studies. Some studies have used a two-alternative forced choice (2AFC) task, while others have used a ratings task. How researchers manipulate facial symmetry also varies; some studies have used faces manipulated to be more (or perfectly) symmetrical, while others have used faces manipulated to be more asymmetrical. Here, across three studies, we evaluate and compare these different methods. In Studies 1 and 2 (N = 340 and 256, respectively), we compare facial symmetry preferences as measured by the 2AFC and ratings tasks. Across both studies, we consistently found a significant preference for facial symmetry when using the 2AFC task, but not with the ratings task. Additionally, correlations between facial symmetry preferences as measured by the two tasks were weak or showed no association. In Study 3, 159 participants rated the attractiveness of faces manipulated to be either symmetrical or more asymmetrical. The asymmetrical faces were rated as significantly less attractive compared to the original faces, while the difference in attractiveness ratings between the original and symmetrical versions was comparatively much smaller. These studies suggest that preference for facial symmetry depends greatly on the study design.

Self-generation and sound intensity interactively modulate perceptual bias, but not perceptual sensitivity

The ability to distinguish self-generated stimuli from those caused by external sources is critical for all behaving organisms. Although many studies point to a sensory attenuation of self-generated stimuli, recent evidence suggests that motor actions can result in either attenuated or enhanced perceptual processing depending on the environmental context (i.e., stimulus intensity). The present study employed 2-AFC sound detection and loudness discrimination tasks to test whether sound source (self- or externally-generated) and stimulus intensity (supra- or near-threshold) interactively modulate detection ability and loudness perception. Self-generation did not affect detection and discrimination sensitivity (i.e., detection thresholds and Just Noticeable Difference, respectively). However, in the discrimination task, we observed a significant interaction between self-generation and intensity on perceptual bias (i.e. Point of Subjective Equality). Supra-threshold self-generated sounds were perceived softer than externally-generated ones, while at near-threshold intensities self-generated sounds were perceived louder than externally-generated ones. Our findings provide empirical support to recent theories on how predictions and signal intensity modulate perceptual processing, pointing to interactive effects of intensity and self-generation that seem to be driven by a biased estimate of perceived loudness, rather by changes in detection and discrimination sensitivity.

Mice in a labyrinth show rapid learning, sudden insight, and efficient exploration

Animals learn certain complex tasks remarkably fast, sometimes after a single experience. What behavioral algorithms support this efficiency? Many contemporary studies based on two-alternative-forced-choice (2AFC) tasks observe only slow or incomplete learning. As an alternative, we study the unconstrained behavior of mice in a complex labyrinth and measure the dynamics of learning and the behaviors that enable it. A mouse in the labyrinth makes ~2000 navigation decisions per hour. The animal explores the maze, quickly discovers the location of a reward, and executes correct 10-bit choices after only 10 reward experiences - a learning rate 1000-fold higher than in 2AFC experiments. Many mice improve discontinuously from one minute to the next, suggesting moments of sudden insight about the structure of the labyrinth. The underlying search algorithm does not require a global memory of places visited and is largely explained by purely local turning rules.