2AFC Research Articles

Flexible and Transparent Electrovibration-Based Haptic Display with Low Driving Voltage.

Electrovibration haptic technology, which provides tactile feedback to users by swiping the surface with a finger via electroadhesion, shows promise as a haptic feedback platform for displays owing to its simple structure, ease of integration with existing displays, and simple driving mechanism. However, without electrical grounding on a user's body, the frequent requirement of a high driving voltage near 50 V limits the use of electrovibration haptic technology in practical display applications. This study introduces materials and fabrication strategies that considerably reduce the driving voltage. We used a transparent poly(vinylidene fluoride) (PVDF) thin film deposited on transparent conductive polymers through a simple spin-coating process, thereby enabling easy integration with existing display technologies. The high dielectric constant characteristics of PVDF enabled the production of tactile cues at low voltages (approximately 15 V), which are within the safety limits of common electronics. We verified the feasibility of our electrovibration haptic feedback system on the basis of the absolute threshold voltage through two-alternative forced choice psychological tests. The results revealed that the PVDF dielectric layer exhibited a relatively lower absolute threshold than commonly used polymer films, which possess a relatively lower dielectric constant. To validate the tactile attributes, a Likert five-point scale survey was conducted, considering flat, concave, and convex curvatures. The results indicated that our haptic device can render diverse surface textures, such as "hairy" and "groovy", on the fingertips through the control of applied pulse width modulated voltage signals.

Loudness and preference judgments for noises of a heat pump

An increasing number of heat pumps have recently been installed to replace conventional heating systems to provide more environmentally friendly and energy-efficient indoor heating. Most commonly, air-to-water heat pumps are chosen. However, the sounds of their fan and compressor can lead to noise complaints and can reach the limit of noise emission regulations. To achieve a more pleasant environment, research is conducted to reduce the perceived noise of heat pumps. As part of an interdisciplinary research project, this study aims to investigate the annoyance ratings of a heat pump and characterize them in terms of equivalent loudness and preference penalties. The study uses a two-alternative forced-choice (2AFC) method with a 1-up-1-down rule to measure the point of subjective equality for six stimuli representing different operation states of the investigated device. This experiment aims to identify differences between loudness and preference, and combined with an evaluation of psychoacoustic parameters, its results are used to improve the acoustics of heat pumps and the overall user experience.

The problem with two-event sequence learning by pigeons

Bonobos appear to show little evidence of learning to make one response (R1) to an AB sequence and a different response (R2) to sequences BB, AA, and BA (Lind et al. PLoS ONE 18(9):e0290546, 2023), yet under different conditions, pigeons can learn this (Weisman et al. Exp Psychol Anim Behav Process 6(4):312, 1980). Aspects of the bonobo procedure may have contributed to this failure. Most important, no response was required in the presence of the stimuli to encourage attention to them. Furthermore, learning to make one response to the target sequence and another to the other sequences involves a bias that allows for better than chance responding. With the two-alternative forced-choice procedure used with the bonobos, the R1 response is correct for one sequence, whereas the R2 response is correct for three sequences. To correct for this, there are three times as many AB trials as each of the other sequences. However, this correction allows a bias to develop in which reinforcement often can be obtained by using only the last stimulus seen as the basis of choice (e.g., when the last stimulus is B respond R1 when the last stimulus is A respond R2). This solution yields reinforcement on five out of six, or 83%, of the trials. In the present experiment with pigeons, using this two-alternative forced choice procedure, most subjects tended to base their choice on the last-seen stimulus. This design allowed subjects to use a suboptimal but relatively effective choice strategy.

Factors Affecting Stimulus Duration Threshold for Depth Discrimination of Asynchronous Targets in the Intermediate Distance Range.

Binocular depth discrimination in the near distance range (< 2 m) improves with stimulus duration. However, whether the same response-pattern holds in the intermediate distance range (approximately 2-25 m) remains unknown because the spatial coding mechanisms are thought to be different. We used the two-interval forced choice procedure to measure absolute depth discrimination of paired asynchronous targets (3, 6, or 16 arc min). The paired targets (0.2 degrees) were located over a distance and height range, respectively, of 4.5 to 7.0m and 0.15 to 0.7 m. Experiment 1 estimated duration thresholds for binocular depth discrimination at varying target durations (40-1610 ms), in the presence of a 2 × 6 array of parallel texture-elements spanning 1.5 × 5.83 m on the floor. The texture-elements provided a visible background in the light-tight room (9 × 3 m). Experiment 2 used a similar setup to control for viewing conditions: binocular versus monocular and with versus without texture background. Experiment 3 compared binocular depth discrimination between brief (40, 80, and 125 ms) and continuous texture background presentation. Stimulus duration threshold for depth discrimination decreased with increasing disparity in experiment 1. Experiment 2 revealed depth discrimination performance with texture background was near chance level with monocular viewing. Performance with binocular viewing degraded without texture background. Experiment 3 showed continuous texture background presentation enhances binocular depth discrimination. Absolute depth discrimination improves with target duration, binocular viewing, and texture background. Performance further improved with longer background duration underscoring the role of ground surface representation in spatial coding.

Beyond balance: The role of the Vestibular system in action recognition

BackgroundAction recognition is a fundamental aspect of human interaction. This process is mediated by the activation of shared sensorimotor representations during action execution and observation. Although complex movements involving balance or head and trunk rotations require vestibular signals for effective execution, their role in the recognition of others' actions is still unknown. ObjectiveTo investigate the causal involvement of the vestibular system in the discrimination of actions performed by others and whether this is influenced by motor familiarity. MethodsIn a single-blind design involving 25 healthy participants, Galvanic Vestibular Stimulation (GVS) was administered during an Action Discrimination Task (ADT), in which videos of actions categorized as vestibular/non-vestibular and familiar/unfamiliar were presented. Following each video, participants were required to identify the climax of the previously viewed action between two image options, using a two-alternative forced choice paradigm. The ADT was performed in active and sham GVS conditions, with left or right anodal montages. Response Times (RTs), Accuracy, and subjective motor familiarity were recorded for each action category. ResultsIn sham GVS condition, an overall familiarity effect was observed, where RTs for familiar actions were faster than RTs for unfamiliar ones, regardless of vestibular engagement (p < .001; ηp2 = .80). Conversely, under active GVS, a selective interference of the identification of vestibular familiar actions was observed compared to sham. Specifically, GVS prolonged RTs for recognizing familiar vestibular actions (p = .004, d = .59) while concurrently enhancing visual sensitivity (d’) for the same actions (p = .03, r = .21). ConclusionThese findings demonstrate the contribution of the vestibular system to action recognition. GVS disrupted the sensorimotor representation of vestibular actions and led to increased reliance on an alternative processing system focused on visual analysis of limb positions. This dissociation provides valuable insights for future investigations into the complex relationship between vestibular signals and cognitive processes involved in action identification, essential for developing innovative GVS interventions, particularly for individuals with sensorimotor or vestibular disorders.

Individual differences in the consistency of neural and behavioural responses to speech sounds

There are documented individual differences among adults in the consistency of speech sound processing, both at neural and behavioural levels. Some adults show more consistent neural responses to speech sounds than others, as measured by an event-related potential called the frequency-following response (FFR); similarly, some adults show more consistent behavioural responses to native speech sounds than others, as measured by two-alternative forced choice (2AFC) and visual analog scaling (VAS) tasks. Adults also differ in how successfully they can perceive non-native speech sounds. Interestingly, it remains unclear whether these differences are related within individuals. In the current study, native English-speaking adults completed native phonetic perception tasks (2AFC and VAS), a non-native (German) phonetic perception task, and an FFR recording session. From these tasks, we derived measures of the consistency of participants’ neural and behavioural responses to native speech as well as their non-native perception ability. We then examined the relationships among individual differences in these measures. Analysis of the behavioural measures revealed that more consistent responses to native sounds predicted more successful perception of unfamiliar German sounds. Analysis of neural and behavioural data did not reveal clear relationships between FFR consistency and our phonetic perception measures. This multimodal work furthers our understanding of individual differences in speech processing among adults, and may eventually lead to individualized approaches for enhancing non-native language acquisition in adulthood.

‘The mirror of the soul?’ Inferring sadness in the eyes

The eyes are widely regarded as the mirror of the soul, providing reliable nonverbal information about drives, feelings, and intentions of others. However, it is unclear how accurate emotion recognition is when only the eyes are visible and whether inferring of emotions is altered across healthy adulthood. To fill this gap, the present piece of research was directed at comparing the ability to infer basic emotions in two groups of typically developing females that differed in age. We set a focus on females seeking group homogeneity. In a face-to-face study, in a two-alternative forced choice paradigm (2AFC), participants had to indicate emotions for faces covered by masks. The outcome reveals that although the recognition pattern is similar in both groups, inferring sadness in the eyes substantially improves with age. Inference of sadness is not only more accurate and less variable in older participants, but also positively correlates with age from early through mid-adulthood. Moreover, reading sadness (and anger) is more challenging in the eyes of male posers. A possible impact of poser gender and cultural background, both in expressing and inferring sadness in the eyes, is highlighted.

Task-based assessment for neural networks: evaluating undersampled MRI reconstructions based on human observer signal detection.

Recent research explores using neural networks to reconstruct undersampled magnetic resonance imaging. Because of the complexity of the artifacts in the reconstructed images, there is a need to develop task-based approaches to image quality. We compared conventional global quantitative metrics to evaluate image quality in undersampled images generated by a neural network with human observer performance in a detection task. The purpose is to study which acceleration (2×, 3×, 4×, 5×) would be chosen with the conventional metrics and compare it to the acceleration chosen by human observer performance. We used common global metrics for evaluating image quality: the normalized root mean squared error (NRMSE) and structural similarity (SSIM). These metrics are compared with a measure of image quality that incorporates a subtle signal for a specific task to allow for image quality assessment that locally evaluates the effect of undersampling on a signal. We used a U-Net to reconstruct under-sampled images with 2×, 3×, 4×, and 5× one-dimensional undersampling rates. Cross-validation was performed for a 500- and a 4000-image training set with both SSIM and MSE losses. A two-alternative forced choice (2-AFC) observer study was carried out for detecting a subtle signal (small blurred disk) from images with the 4000-image training set. We found that for both loss functions, the human observer performance on the 2-AFC studies led to a choice of a 2× undersampling, but the SSIM and NRMSE led to a choice of a 3× undersampling. For this detection task using a subtle small signal at the edge of detectability, SSIM and NRMSE led to an overestimate of the achievable undersampling using a U-Net before a steep loss of image quality between 2×, 3×, 4×, 5× undersampling rates when compared to the performance of human observers in the detection task.

Lombard speech detection in case of spatial separation between noise source and talkers of different genders

The spatial selectivity of hearing to speech signals was studied when the target signal and interference were separated by distance between their sources and the listener. In the work, the hypothesis about the improvement of hearing selectivity due to more intensive activation of the high-frequency binaural mechanism due to the shift of the speaker’s voice spectrum occurs in noisy environment towards high frequencies, was tested. The thresholds for detecting the target signal – a two-syllable word uttered by male or female, were evaluated in the two-alternative two-interval forced choice paradigm in 4 series. Series differed by the type of target signal (ordinary or Lombard speech) and the location of target source and noise (multi-talker noise) one. The both sources were located at a distance of 1 and 4 m opposite the subject at the level of his head. The detection threshold was defined as the ratio of signal and noise levels at the listener’s place (S/N). The threshold for detecting the target signal (male and female speaker voices together) was -11 dB S/N for ordinary as well as Lombard speech. It did not depend on which of the sources - the target signal or noise, was closer to the listener. In normal speech, the detection thresholds on average differed for male and female voices, but the difference was not significant. In Lombard speech, these thresholds were significantly different: for a male voice, the threshold at a detection level of 0.67 was -10 dB S/N, and for a female voice – -12.5 dB S/N.

Sensorimotor adaptation impedes perturbation detection in grasping.

Humans achieve skilled actions by continuously correcting for motor errors or perceptual misjudgments, a process called sensorimotor adaptation. This can occur with the actor both detecting (explicitly) and not detecting the error (implicitly). We investigated how the magnitude of a perturbation and the corresponding error signal each contribute to the detection of a size perturbation during interaction with real-world objects. Participants grasped cuboids of different lengths in a mirror-setup allowing us to present different sizes for seen and felt cuboids, respectively. Visuo-haptic size mismatches (perturbations) were introduced either abruptly or followed a sinusoidal schedule. These schedules dissociated the error signal from the visuo-haptic mismatch: Participants could fully adapt their grip and reduce the error when a perturbation was introduced abruptly and then stayed the same, but not with a constantly changing sinusoidal perturbation. We compared participants' performance in a two-alternative forced choice (2AFC) task where participants judged these mismatches, and modelled error-correction in grasping movements by looking at changes in maximum grip apertures, measured using motion tracking. We found similar mismatch-detection performance with sinusoidal perturbation schedules and the first trial after an abrupt change, but decreasing performance over further trials for the latter. This is consistent with the idea that reduced error signals following adaptation make it harder to detect perturbations. Error-correction parameters indicated stronger error-correction in abruptly introduced perturbations. However, we saw no correlation between error-correction and overall mismatch-detection performance. This emphasizes the distinct contributions of the perturbation magnitude and the error signal in helping participants detect sensory perturbations.

A deep learning anthropomorphic model observer for a detection task in PET.

Lesion detection is one of the most important clinical tasks in positron emission tomography (PET) for oncology. An anthropomorphic model observer (MO) designed to replicate human observers (HOs) in a detection task is an important tool for assessing task-based image quality. The channelized Hotelling observer (CHO) has been the most popular anthropomorphic MO. Recently, deep learning MOs (DLMOs), mostly based on convolutional neural networks (CNNs), have been investigated for various imaging modalities. However, there have been few studies on DLMOs for PET. The goal of the study is to investigate whether DLMOs can predict HOs better than conventional MOs such as CHO in a two-alternative forced-choice (2AFC) detection task using PET images with real anatomical variability. Two types of DLMOs were implemented: (1) CNN DLMO, and (2) CNN-SwinT DLMO that combines CNN and Swin Transformer (SwinT) encoders. Lesion-absent PET images were reconstructed from clinical data, and lesion-present images were reconstructed with adding simulated lesion sinogram data. Lesion-present and lesion-absent PET image pairs were labeled by eight HOs consisting of four radiologists and four image scientists in a 2AFC detection task. In total, 2268 pairs of lesion-present and lesion-absent images were used for training, 324 pairs for validation, and 324 pairs for test. CNN DLMO, CNN-SwinT DLMO, CHO with internal noise, and non-prewhitening matched filter (NPWMF) were compared in the same train-test paradigm. For comparison, six quantitative metrics including prediction accuracy, mean squared errors (MSEs) and correlation coefficients, which measure how well a MO predicts HOs, were calculated in a 9-fold cross-validation experiment. In terms of the accuracy and MSE metrics, CNN DLMO and CNN-SwinT DLMO showed better performance than CHO and NPWMF, and CNN-SwinT DLMO showed the best performance among the MOs evaluated. DLMO can predict HOs more accurately than conventional MOs such as CHO in PET lesion detection. Combining SwinT and CNN encoders can improve the DLMO prediction performance compared to using CNN only.

Competitive (but not cooperative) body odors bias the discrimination of action intentions towards cooperation

Odors help us to interpret the environment, including the nature of social interactions. But, whether and how they influence the ability to discriminate the intentional states embedded in actions is unclear. In two experiments, we asked two independent groups of participants to discriminate motor intentions from videos showing one agent performing a reach-to-grasp movement with another agent with a cooperative or a competitive intent, and the same movement performed alone at either natural- or fast-speed, as controls. Task-irrelevant odor primes preceded each video presentation. Experiment 1 (N = 19) included masked cooperative and competitive body odors (human sweat collected while the donors were engaged in cooperative and competitive activities), whereas Experiment 2 (N = 20) included a common odor (cedarwood oil) and no odor (clean air) as primes. In an odor-primed, two-alternative forced choice task, participants discriminated the intention underlying the observed action. The results indicated that the odor exposure modulated the discrimination speed across different intentions, but only when the action intentions were hard to discriminate (cooperative vs. individual natural-speed, and competitive vs. individual fast-speed). Contrary to our hypothesis, a direct odor-action intention compatibility effect was not found. Instead, we propose a negative arousal compatibility-like effect to explain our results. Discrimination of high arousing action intentions (i.e., competitive) took longer when primed by high arousing odors (common odor and competitive body odor) than by low arousing odors (cooperative body odor and no odor). Discrimination of low arousing action intentions (i.e., cooperative) took longer when primed by low arousing odors than by high arousing odors. All in all, competitive (but not cooperative) body odors bias the discrimination of action intentions towards cooperation.

Investigating the crowding effect on letters and symbols in deaf adults

Reading requires the transformation of a complex array of visual features into sounds and meaning. For deaf signers who experience changes in visual attention and have little or no access to the sounds of the language they read, understanding the visual constraints underlying reading is crucial. This study aims to explore a fundamental aspect of visual perception intertwined with reading: the crowding effect. This effect manifests as the struggle to distinguish a target letter when surrounded by flanker letters. Through a two-alternative forced choice task, we assessed the recognition of letters and symbols presented in isolation or flanked by two or four characters, positioned either to the left or right of fixation. Our findings reveal that while deaf individuals exhibit higher accuracy in processing letters compared to symbols, their performance falls short of that of their hearing counterparts. Interestingly, despite their proficiency with letters, deaf individuals didn’t demonstrate quicker letter identification, particularly in the most challenging scenario where letters were flanked by four characters. These outcomes imply the development of a specialized letter processing system among deaf individuals, albeit one that may subtly diverge from that of their hearing counterparts.

Sometimes memory misleads: Variants of the error-speed effect strengthen the evidence for systematically misleading memory signals in recognition memory.

The error-speed effect describes the observation that the speed of recognition errors in a first binary recognition task predicts the response accuracy in a subsequent two-alternative forced-choice (2AFC) task that comprises the erroneously judged items of the first task. So far, the effect has been primarily explained by the assumption that some error responses result from misleading memory evidence. However, it is also possible that the effect arises because participants remember and use their response times from the binary task to solve the 2AFC task. Furthermore, the phenomenon is quite new and its robustness or generalizability across other recognition tasks (e.g., a confidence-rating task) remains to be demonstrated. The aim of the present study is to address these limitations by introducing a new variant of the error-speed effect, replacing the 2AFC task with a confidence-rating task (Experiment 1), and by reversing task order (Experiment 2) to test whether participants employ a response-time strategy. In both experiments, we collected data using a sequential probability ratio t-test procedure and found evidence in favor of the hypothesis that the speed of binary recognition errors predicts confidence ratings for the same stimulus. These results attest to the robustness and generalizability of the error-speed effect and reveal that at least some errors must be due to systematically misleading memory evidence.

Not so peculiar after all: On the normal position of arguments of German experiencer-object verbs

The present paper argues that seemingly erratic linearisation patterns of experiencer-object&amp;nbsp;verbs in German can be accounted for by considering well-known linearisation constraints.&amp;nbsp;The analysis is based on two Two-Alternative Forced-Choice experiments: The first study tests&amp;nbsp;experiencer-object verbs with inanimate subjects, the second one tests experiencer-object verbs&amp;nbsp;with animate subjects. If the subject is inanimate, experiencer-object verbs selecting a dative&amp;nbsp;object (e.g., behagen &amp;lsquo;to please&amp;rsquo;) prefer an object-before-subject linearisation while the ones&amp;nbsp;selecting an accusative object (e.g., bezaubern &amp;lsquo;to charm&amp;rsquo;) lean towards subject before object.&amp;nbsp;With animate subjects, accusative-object experiencer-object verbs prefer subject before object,&amp;nbsp;while there is no clear preference for dative-object experiencer-object verbs. An explorative&amp;nbsp;investigation reveals verb-specific differences that call into question the case-based classes. We&amp;nbsp;argue that linearisation preferences of experiencer-object verbs in German should be analysed&amp;nbsp;by coupling free base generation with violable linearisation constraints. We provide an analysis&amp;nbsp;along these lines, which is based on a semantic distinction and does not require case-based&amp;nbsp;constraints.

Knowing that you know that you know? An extreme-confidence heuristic can lead to above-chance discrimination of metacognitive performance.

In daily life, we can not only estimate confidence in our inferences ('I'm sure I failed that exam'), but can also estimate whether those feelings of confidence are good predictors of decision accuracy ('I feel sure I failed, but my feeling is probably wrong; I probably passed'). In the lab, by using simple perceptual tasks and collecting trial-by-trial confidence ratings visual metacognition research has repeatedly shown that participants can successfully predict the accuracy of their perceptual choices. Can participants also successfully evaluate 'confidence in confidence' in these tasks? This is the question addressed in this study. Participants performed a simple, two-interval forced choice numerosity task framed as an exam. Confidence judgements were collected in the form of a 'predicted exam grade'. Finally, we collected 'meta-metacognitive' reports in a two-interval forced-choice design: trials were presented in pairs, and participants had to select that in which they thought their confidence (predicted grade) best matched their accuracy (actual grade), effectively minimizing their quadratic scoring rule (QSR) score. Participants successfully selected trials on which their metacognition was better when metacognitive performance was quantified using area under the type 2 ROC (AUROC2) but not when using the 'gold-standard' measure m-ratio. However, further analyses suggested that participants selected trials on which AUROC2 is lower in part via an extreme-confidence heuristic, rather than through explicit evaluation of metacognitive inferences: when restricting analyses to trials on which participants gave the same confidence rating AUROC2 no longer differed as a function of selection, and likewise when we excluded trials on which extreme confidence ratings were given. Together, our results show that participants are able to make effective metacognitive discriminations on their visual confidence ratings, but that explicit 'meta-metacognitive' processes may not be required.

Value-based decision-making in regular alcohol consumers following experimental manipulation of alcohol value

BackgroundDevaluation of alcohol leads to reductions in alcohol choice and consumption; however, the cognitive mechanisms that underpin this relationship are not well-understood. In this study we applied a computational model of value-based decision-making (VBDM) to decisions made about alcohol and alcohol-unrelated cues following experimental manipulation of alcohol value. Method: Using a pre-registered within-subject design, thirty-six regular alcohol consumers (≥14 UK units per week) completed a two-alternative forced choice task where they chose between two alcohol images (in one block) or two soft drink images (in a different block) after watching videos that emphasised the positive (alcohol value), and separately, the negative (alcohol devalue) consequences of alcohol. On each block, participants pressed a key to select the image depicting the drink they would rather consume. A drift–diffusion model (DDM) was fitted to reaction time and choice data to estimate evidence accumulation (EA) processes and response thresholds during the different blocks in each experimental condition. Findings: In the alcohol devalue condition, soft drink EA rates were significantly higher compared to alcohol EA rates (p = 0.04, d = 0.31), and compared to soft drink EA rates in the alcohol value condition (p = 0.01, d = 0.38). However, EA rates for alcoholic drinks and response thresholds (for either drink type) were unaffected by the experimental manipulation. Conclusions: In line with behavioural economic models of addiction that emphasise the important role of alternative reinforcement, experimentally manipulating alcohol value is associated with changes in the internal cognitive processes that precede soft drink choice.

Synergistic effect of combining umami substances enhances perceived saltiness

Umami substances have the potential to enhance the perception of saltiness and thus reduce sodium intake. Two sensory evaluation experiments were conducted, involving participants tasting salt solutions, and solutions with added umami substances at equal sodium concentrations. Umami substances included sodium glutamate (MSG), disodium inosinate (IMP), and the combination of them which has a synergistic effect and is a closer match to commonly-consumed foods. In Experiment 1, using the two-alternative forced-choice (2-AFC) method by 330 consumers, paired comparisons were conducted at three different sodium concentrations. The combination of MSG and IMP enhanced the perception of saltiness (p < .001 in the difference test), whereas presenting either umami substance in isolation failed to do so (p > .05 in the similarity test). Significant order effects occurred in paired comparisons. In Experiment 2, a two-sip time-intensity (TI) analysis with trained panellists verified these results and found that tasting MSG and IMP either simultaneously or successively enhanced saltiness perception at equal sodium concentrations. These findings indicate that the synergistic effect of umami substances may be the cause of saltiness enhancement, and represents a potential strategy for sodium reduction while satisfying the consumer demand for saltiness perception. Considering the application in food processing and in food pairing, umami substances can potentially be used to help to reduce salt intake in food consumption.

Exploring individual differences in native phonetic perception and their link to nonnative phonetic perception.

Adults differ considerably in their perception of both native and nonnative phonemes. For instance, when presented with continua of native phonemes on two-alternative forced choice (2AFC) or visual analog scaling (VAS) tasks, some people show sudden changes in responses (i.e., steep identification slopes) and others show gradual changes (i.e., shallow identification slopes). Moreover, some adults are more successful than others at learning unfamiliar phonemes. The predictors of these individual differences and the relationships between them are poorly understood. It also remains unclear to what extent different tasks (2AFC vs. VAS) may reflect distinct individual differences in perception. In two experiments, we addressed these questions by examining the relationships between individual differences in performance on native and nonnative phonetic perception tasks. We found that shallow 2AFC identification slopes were not related to shallow VAS identification slopes but were related to inconsistent VAS responses. Additionally, our results suggest that consistent native perception may play a role in promoting successful nonnative perception. These findings help characterize the nature of individual differences in phonetic perception and contribute to our understanding of how to measure such differences. This work also has implications for encouraging successful acquisition of new languages in adulthood. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Modeling human observer detection for varying data acquisition in undersampled MRI for two-alternative forced choice (2-AFC) and forced localization tasks.

Undersampling in the frequency domain (k-space) in MRI enables faster data acquisition. In this study, we used a fixed 1D undersampling factor of 5x with only 20% of the k-space collected. The fraction of fully acquired low k-space frequencies were varied from 0% (all aliasing) to 20% (all blurring). The images were reconstructed using a multi-coil SENSE algorithm. We used two-alternative forced choice (2-AFC) and the forced localization tasks with a subtle signal to estimate the human observer performance. The 2-AFC average human observer performance remained fairly constant across all imaging conditions. The forced localization task performance improved from the 0% condition to the 2.5% condition and remained fairly constant for the remaining conditions, suggesting that there was a decrease in task performance only in the pure aliasing situation. We modeled the average human performance using a sparse-difference of Gaussians (SDOG) Hotelling observer model. Because the blurring in the undersampling direction makes the mean signal asymmetric, we explored an adaptation for irregular signals that made the SDOG template asymmetric. To improve the observer performance, we also varied the number of SDOG channels from 3 to 4. We found that despite the asymmetry in the mean signal, both the symmetric and asymmetric models reasonably predicted the human performance in the 2-AFC experiments. However, the symmetric model performed slightly better. We also found that a symmetric SDOG model with 4 channels implemented using a spatial domain convolution and constrained to the possible signal locations reasonably modeled the forced localization human observer results.