Alternative Forced Choice Task Research Articles

Simultaneous modulation of pulse charge and burst period elicits two differentiable referred sensations

Objective.To investigate the feasibility of delivering multidimensional feedback using a single channel of peripheral nerve stimulation by complementing intensity percepts with flutter frequency percepts controlled by burst period modulation.Approach.Two dimensions of a distally referred sensation were provided simultaneously: intensity was conveyed by the modulation of the pulse charge rate inside short discrete periods of stimulation referred to as bursts and frequency was conveyed by the modulation of the period between bursts. For this approach to be feasible, intensity percepts must be perceived independently of frequency percepts. Two experiments investigated these interactions. A series of two alternative forced choice tasks (2AFC) were used to investigate burst period modulation's role in intensity discernibility. Magnitude estimation tasks were used to determine any interactions in the gradation between the frequency and intensity percepts.Main results.The 2AFC revealed that burst periods can be individually differentiated as a gradable frequency percept in peripheral nerve stimulation. Participants could correctly rate a perceptual scale of intensity and frequency regardless of the value of the second, but the dependence of frequency differentiability on charge rate indicates that frequency was harder to detect with weaker intensity percepts. The same was not observed in intensity differentiability as the length of burst periods did not significantly alter intensity differentiation. These results suggest multidimensional encoding is a promising approach for increasing information throughput in sensory feedback systems if intensity ranges are selected properly.Significance.This study offers valuable insights into haptic feedback through the peripheral nervous system and demonstrates an encoding approach for neural stimulation that may offer enhanced information transfer in virtual reality applications and sensory-enabled prosthetic systems. This multidimensional encoding strategy for sensory feedback may open new avenues for enriched control capabilities.

Coexistence of state, choice, and sensory integration coding in barrel cortex LII/III

During perceptually guided decisions, correlates of choice are found as upstream as in the primary sensory areas. However, how well these choice signals align with early sensory representations, a prerequisite for their interpretation as feedforward substrates of perception, remains an open question. We designed a two alternative forced choice task (2AFC) in which male mice compared stimulation frequencies applied to two adjacent vibrissae. The optogenetic silencing of individual columns in the primary somatosensory cortex (wS1) resulted in predicted shifts of psychometric functions, demonstrating that perception depends on focal, early sensory representations. Functional imaging of layer II/III single neurons revealed mixed coding of stimuli, choices and engagement in the task. Neurons with multi-whisker suppression display improved sensory discrimination and had their activity increased during engagement in the task, enhancing selectively representation of the signals relevant to solving the task. From trial to trial, representation of stimuli and choice varied substantially, but mostly orthogonally to each other, suggesting that perceptual variability does not originate from wS1 fluctuations but rather from downstream areas. Together, our results highlight the role of primary sensory areas in forming a reliable sensory substrate that could be used for flexible downstream decision processes.

A reliable and efficient adaptive Bayesian method to assess static lower limb position sense

BackgroundLower limb proprioception is critical for maintaining stability during gait and may impact how individuals modify their movements in response to changes in the environment and body state, a process termed “sensorimotor adaptation”. However, the connection between lower limb proprioception and sensorimotor adaptation during human gait has not been established. We suspect this gap is due in part to the lack of reliable, efficient methods to assess global lower limb proprioception in an ecologically valid context. New MethodWe assessed static lower limb proprioception using an alternative forced choice task, administered twice to determine test-retest reliability. Participants stood on a dual-belt treadmill which passively moved one limb to stimulus locations selected by a Bayesian adaptive algorithm. At the stimulus locations, participants judged relative foot positions and the algorithm estimated the point of subjective equality (PSE) and the uncertainty of lower limb proprioception. ResultsUsing the Bland-Altman method, combined with Bayesian statistics, we found that both the PSE and uncertainty estimates had good reliability. Comparison with existing method(s)Current methods assessing static lower limb proprioception do so within a single joint, in non-weight bearing positions, and rely heavily on memory. One exception assessed static lower limb proprioception in standing but did not measure reliability and contained confounds impacting participants’ judgments, which we experimentally controlled here. ConclusionsThis efficient and reliable method assessing lower limb proprioception will aid future mechanistic understanding of locomotor adaptation and serve as a useful tool for basic and clinical researchers studying balance and falls.

Optimizing data acquisition in undersampled magnetic resonance imaging (MRI) using two alternative forced choice (2-AFC) and search tasks.

Undersampling in the frequency domain (k-space) in MRI accelerates the data acquisition. Typically, a fraction of the low frequencies is fully collected and the rest are equally undersampled. We used a fixed 1D undersampling factor of 5x where 20% of the k-space lines are collected but varied the fraction of the low k-space frequencies that are fully sampled. We used a range of fully acquired low k-space frequencies from 0% where the primary artifact is aliasing to 20% where the primary artifact is blurring in the undersampling direction. Small lesions were placed in the coil k-space data for fluid-attenuated inversion recovery (FLAIR) brain images from the fastMRI database. The images were reconstructed using a multi-coil SENSE reconstruction with no regularization. We conducted a human observer two-alternative forced choice (2-AFC) study with a signal known exactly and a search task with variable backgrounds for each of the acquisitions. We found that for the 2-AFC task, the average human observer did better with more of the low frequencies being fully sampled. For the search task, we found that after an initial improvement from having none of the low frequencies fully sampled to just 2.5%, the performance remained fairly constant. We found that the performance in the two tasks had a different relationship to the acquired data. We also found that the search task was more consistent with common practice in MRI where a range of frequencies between 5% and 10% of the low frequencies are fully sampled.

Is visual metacognition associated with autistic traits? A regression analysis shows no link between visual metacognition and Autism-Spectrum Quotient scores

Metacognition —the human ability to recognize correct decisions— is a key cognitive process linked to learning and development. Several recent studies investigated the relationship between metacognition and autism. However, the evidence is still inconsistent. While some studies reported autistic people having lower levels of metacognitive sensitivity, others did not. Leveraging the fact that autistic traits are present in the general population, our study investigated the relationship between visual metacognition and autistic traits in a sample of 360 neurotypical participants. We measured metacognition as the correspondence between confidence and accuracy in a visual two alternative forced choice task. Autistic-traits were assessed through the Autism-spectrum Quotient (AQ) score. A regression analysis revealed no statistically significant association between autistic traits and metacognition or confidence. Furthermore, we found no link between AQ sub-scales and metacognition. We do not find support for the hypothesis that autistic traits are associated with metacognition in the general population.

Experimental Enhancement of Feelings of Transcendence, Tenderness, and Expressiveness by Music in Christian Liturgical Spaces.

In western cultures, when it comes to places of worship and liturgies, music, acoustics and architecture go hand in hand. In the present study, we aimed to investigate whether the emotions evoked by music are enhanced by the acoustics of the space where the music was composed to be played on. We explored whether the emotional responses of western naïve listeners to two vocal pieces from the Renaissance, one liturgical and one secular, convolved with the impulse responses of four Christian temples from the United Kingdom, were modulated by the appropriate piece/space matching. In an alternative forced choice task where participants had to indicate their preference for the original recording of the piece (not convolved with any temple-like acoustics) vs. the convolved one, no significant differences were found. However, in the tasks where participants rated their emotional in response to each piece and acoustic condition, the factorial ANCOVA analyses performed on the results revealed significant effects. We observed that, across pieces and spaces, participants found the temple-like acoustics as more transcendent, compared to the acoustics of the original version of the pieces. In addition, they rated the secular piece as more tender and the liturgical piece as more expressive in its original versions, compared to the convolved ones. We conclude that the acoustic signature of the four Christian temples causes an exaltation of certain emotions on listeners, although this effect is not associated to one or another musical piece.

Behavior as a stereotype cue: An European Portuguese pretest on age and gender stereotypes

When it comes to the study of stereotypes, plenty of material can be of use. While personality traits tend to be the most commonly adopted, behavioral information can also be relevant, both in the study of stereotypes, as well as in other research fields (e.g., illusory correlations, memory and judgement and decision making). The purpose of this paper was to create a readily available list of behavioral sentences with stereotypicality ratings for both age (young to old) and gender (woman to man) categories, to be used in future studies. In two studies, participants judged age and gender stereotypicality of more than two hundred sentences in European Portuguese. Results were stable across both studies, using different methodologies (three alternative forced-choice task, in Study 1; bipolar rating scale, in Study 2). Relative frequencies for each choice, as well as average ratings, per behavior, are provided at the end.

Cognitive load influences oculomotor behavior in natural scenes

Cognitive neuroscience researchers have identified relationships between cognitive load and eye movement behavior that are consistent with oculomotor biomarkers for neurological disorders. We develop an adaptive visual search paradigm that manipulates task difficulty and examine the effect of cognitive load on oculomotor behavior in healthy young adults. Participants (N = 30) free-viewed a sequence of 100 natural scenes for 10 s each, while their eye movements were recorded. After each image, participants completed a 4 alternative forced choice task in which they selected a target object from one of the previously viewed scenes, among 3 distracters of the same object type but from alternate scenes. Following two correct responses, the target object was selected from an image increasingly farther back (N-back) in the image stream; following an incorrect response, N decreased by 1. N-back thus quantifies and individualizes cognitive load. The results show that response latencies increased as N-back increased, and pupil diameter increased with N-back, before decreasing at very high N-back. These findings are consistent with previous studies and confirm that this paradigm was successful in actively engaging working memory, and successfully adapts task difficulty to individual subject’s skill levels. We hypothesized that oculomotor behavior would covary with cognitive load. We found that as cognitive load increased, there was a significant decrease in the number of fixations and saccades. Furthermore, the total duration of saccades decreased with the number of events, while the total duration of fixations remained constant, suggesting that as cognitive load increased, subjects made fewer, longer fixations. These results suggest that cognitive load can be tracked with an adaptive visual search task, and that oculomotor strategies are affected as a result of greater cognitive demand in healthy adults.

Using the phase inversion method and loudness comparisons for the evaluation of noise reduction algorithms in hearing aids

The phase inversion method, a technical measurement procedure, is often used to evaluate the performance of noise reduction algorithms in hearing aids. However, a detailed comparison of these technical measurements with the perceived loudness is missing. Therefore, commercially available hearing aids of six different manufacturers were evaluated technically and in a study with 18 normal-hearing listeners. First, the output signals of the hearing aids with and without activated noise reduction were recorded in a test box. Then, the test subjects evaluated the perceived loudness of these recordings within multiple two alternative forced choice (2-AFC) tasks. During one task, the test subjects had to focus either on the speech or noise signal and were asked to select the louder of two signals, which both contained a mixture of speech and noise. These results provide not only the perceived SNR but also the perceived speech and noise levels. Comparing the results of the 2-AFC tasks and the phase inversion method basically shows good agreement. Nevertheless, a simple computation of the sound pressure level can lead to significant deviations. Therefore, another possibility for the analysis of the results of the phase inversion method to better match the perceived loudness is presented.

No temporal contrast enhancement of simple decreases in noxious heat.

Offset analgesia (OA) studies have found that small decreases in the intensity of a tonic noxious heat stimulus yield a disproportionately large amount of pain relief. In the classic OA paradigm, the decrease in stimulus intensity is preceded by an increase of equal size from an initial noxious level. Although the majority of researchers believe this temporal sequence of two changes is important for eliciting OA, it has also been suggested that the temporal contrast mechanism underlying OA may enhance detection of simple, isolated decreases in noxious heat. To test whether decreases in noxious heat intensity, by themselves, are perceived better than increases of comparable sizes, we used an adaptive two-interval alternative forced choice task to find perceptual thresholds for increases and decreases in radiant and contact heat. Decreases in noxious heat were more difficult to perceive than increases of comparable sizes from the same initial temperature of 45°C. In contrast, decreases and increases were perceived equally well within a common range of noxious temperatures (i.e., when increases started from 45°C and decreases started from 47°C). In another task, participants rated the pain intensity of heat stimuli that randomly and unpredictably increased, decreased, or remained constant. Ratings of unpredictable stimulus decreases also showed no evidence of perceptual enhancement. Our results demonstrate that there is no temporal contrast enhancement of simple, isolated decreases in noxious heat intensity. Combined with previous OA findings, they suggest that long-lasting noxious stimuli that follow an increase-decrease pattern may be important for eliciting the OA effect.NEW & NOTEWORTHY Previous research suggested that a small decrease in noxious heat intensity feels surprisingly large because of sensory enhancement of noxious stimulus offsets (a simplified form of “offset analgesia”). Using a two-alternative forced choice task where participants detected simple increases or decreases in noxious heat, we showed that decreases in noxious heat, by themselves, are no better perceived than increases of comparable sizes. This suggests that a decrease alone is not sufficient to elicit offset analgesia.

The Effects of Visual Cues, Blindfolding, Synesthetic Experience, and Musical Training on Pure-Tone Frequency Discrimination.

How perceptual limits can be reduced has long been examined by psychologists. This study investigated whether visual cues, blindfolding, visual-auditory synesthetic experience, and musical training could facilitate a smaller frequency difference limen (FDL) in a gliding frequency discrimination test. Ninety university students, with no visual or auditory impairment, were recruited for this one-between (blindfolded/visual cues) and one-within (control/experimental session) designed study. Their FDLs were tested by an alternative forced-choice task (gliding upwards/gliding downwards/no change) and two questionnaires (Vividness of Mental Imagery Questionnaire and Projector–Associator Test) were used to assess their tendency to synesthesia. The participants provided with visual cues and with musical training showed a significantly smaller FDL; on the other hand, being blindfolded or having a synesthetic experience before could not significantly reduce the FDL. However, no pattern was found between the perception of the gliding upwards and gliding downwards frequencies. Overall, the current study suggests that the inter-sensory perception can be enhanced through the training and facilitation of visual–auditory interaction under the multiple resource model. Future studies are recommended in order to verify the effects of music practice on auditory percepts, and the different mechanisms between perceiving gliding upwards and downwards frequencies.

Распознавание эмоций в условиях ступенчатой стробоскопической экспозиции выражений лица

We studied the perception of human facial emotional expressions during step-function stroboscopic presentation of changing mimics. Consecutive stages of each of the six basic facial expressions were pre sented to the participants: neutral face (300 ms) — expression of medium intensity (10—40 ms) — intense expression (30—120 ms) — expression of medium intensity (10—40 ms) — neutral face (100 ms). Alternative forced choice task was used to categorize the facial expressions. The results were compared to previous studies (Barabanschikov, Korolkova, Lobodinskaya, 2015; 2016), conducted using the same paradigm but with boxcar-function change of the expression: neutral face — intense expression — neutral face. We found that the dynamics of facial expression recognition, as well as errors and recognition time are almost identical in conditions of boxcar- and step-function presentation. One factor influencing the recognition rate is the proportion of presentation time of static (neutral) and changing (facial expression) aspects of the stimulus. In suboptimal conditions of facial expression perception (minimal presentation time of 10+30+10 ms and reduced intensity of expressions) we revealed stroboscopic sensibilization — a previously described phenomenon of enhanced recognition rate of low-attractive expressions (disgust, sadness, fear and anger), which has been previously found in conditions of boxcar-function presentation of expressions. We confirmed the similarity of influence of real and apparent motion on the recognition of basic facial emotional expressions.

Visual acuity in the striped skunk (Mephitis mephitis).

The visual acuity of striped skunks (Mephitis mephitis) was tested using a 2 alternative forced-choice task with square wave gratings. Skunks were reinforced with food items for touching a ball in front of a striped stimulus when paired with a ball in front of a solid gray stimulus. Skunks demonstrated a maximum visual acuity of 0.42 cycles per degree when tested with bright outdoor illumination. This poor visual acuity may be due to their nocturnal lifestyle, lack of predation, and is consistent with their preferential use of smell and sound during foraging. (PsycINFO Database Record

Auditory perception of object properties as inverse acoustics

Perception relies on regularities in sensory data that are caused by physical laws. In audition, physical laws governing object interactions constrain the structure of sounds. However, it remains unclear to what extent these constraints have been internalized by the brain to support auditory inferences about the world. To investigate whether physical constraints are modeled by the auditory system, we developed a Bayesian ideal observer for a physics-inspired generative model of impact sounds, and tested whether its judgments of the mass of a ball falling onto a board accorded with those of human listeners. To generate audio with the model, the time-varying impact force was convolved with measured impulse responses of the ball and board. The force varied parametrically with mass to simulate impacts involving balls of different masses. This relationship was fitted to measurements of a set of wooden balls with equal hardness. Inference was performed by Markov chain Monte Carlo sampling. The model accurately predicted most human judgments in a two alternative forced choice task using recorded audio. However, the model underestimated mass when the ball material was harder than wood. The results suggest that additional physical parameters (e.g., hardness) must be modeled to account for human perception.

Raising the alarm: Individual differences in the perceptual awareness of masked facial expressions

A theoretical concern in addressing the unconscious perception of emotion is the extent to which participants can access experiential properties of masked facial stimuli. Performance on a two alternative forced choice (2AFC) task as a measure of objective awareness was compared with a new measure developed to access experiential phenomena of the target-mask transition, the perceptual contrast-change sensitivity (PCCS) measure in a backward-masking paradigm with angry, happy and neutral facial expressions. Whilst 2AFC performance indicated that the targets were successfully masked, PCCS values were significantly higher in the happy-neutral face condition than in the angry-neutral face and the neutral-neutral face conditions (Experiment 1). Furthermore, objective measures of awareness were more readily displayed by individuals with high trait anxiety, whereas individuals with low trait anxiety showed greater access to the experiential quality of happy faces (Experiment 2). These findings provide important insights into the methodological considerations involved in the study of non-conscious processing of emotions, both with respect to individual differences in anxiety and the extent to which certain expressions can be successfully masked relative to others. Furthermore, our results may be informative to work investigating the neural correlates of conscious versus unconscious perception of emotion.

Decision Dynamics in Groups with Interacting Members

Group decisions involve the combination of evidence accumulation by individual members and direct member-to-member interactions. We consider a simplified framework of two deciders, each undergoing a two alternative forced choice task, with the choices of early deciding members biasing members who have yet to choose. We model decision dynamics as a drift-diffusion process and present analysis of the associated Fokker--Planck equation for the group. We show that the probability of coordinated group decisions (both members make the same decision) is maximized by setting the decision threshold of one member to a lower value than its neighbor's. This result is akin to a speed-accuracy tradeoff, where the penalty of lowering the decision threshold is choice inaccuracy while the benefit is that earlier decisions have a higher probability of influencing the other member. We numerically extend these results to large group decisions, where it is shown that by choosing the appropriate parameters, a small but decisive sub-group of the population can have a large amount of influence on the total group.

Residual perception of biological motion in cortical blindness

From birth, the human visual system shows a remarkable sensitivity for perceiving biological motion. This visual ability relies on a distributed network of brain regions and can be preserved even after damage of high-level ventral visual areas. However, it remains unknown whether this critical biological skill can withstand the loss of vision following bilateral striate damage. To address this question, we tested the categorization of human and animal biological motion in BC, a rare case of cortical blindness after anoxia-induced bilateral striate damage. The severity of his impairment, encompassing various aspects of vision (i.e., color, shape, face, and object recognition) and causing blind-like behavior, contrasts with a residual ability to process motion. We presented BC with static or dynamic point-light displays (PLDs) of human or animal walkers. These stimuli were presented either individually, or in pairs in two alternative forced choice (2AFC) tasks. When confronted with individual PLDs, the patient was unable to categorize the stimuli, irrespective of whether they were static or dynamic. In the 2AFC task, BC exhibited appropriate eye movements towards diagnostic information, but performed at chance level with static PLDs, in stark contrast to his ability to efficiently categorize dynamic biological agents. This striking ability to categorize biological motion provided top-down information is important for at least two reasons. Firstly, it emphasizes the importance of assessing patients’ (visual) abilities across a range of task constraints, which can reveal potential residual abilities that may in turn represent a key feature for patient rehabilitation. Finally, our findings reinforce the view that the neural network processing biological motion can efficiently operate despite severely impaired low-level vision, positing our natural predisposition for processing dynamicity in biological agents as a robust feature of human vision.

Effects of a listener’s very slow rotation on sound localization accuracy

A listener’s head movement is effectively used to accurately localize sounds. By contrast, when a sound stimulus is presented during head rotation, sound localization acuity decreases. Previous studies have shown that sound localization accuracy is degraded even during slow head rotation at 50/s. In this study, we investigated the sound localization accuracy during very slow head rotation from 0.6250/s to 50/s. We measured the detection thresholds (DTs) at the listener’s subjective front. The experiment consisted of static and rotation conditions. Listeners were asked to report whether a 30 ms noise burst was presented from the left or right of the subjective front (2 Alternative Forced Choice Task). In the results, the DTs in the rotation condition were larger than that in the static condition. Moreover, DTs seem almost independent of the rotation speed. This suggests that the sound localization resolution at the subjective front is degraded by a listener's passive rotation irrespective of the rotation s...

Influence of sound source arrangement on the precedence effect

As such robot audition, problem of estimating the direction of the sound image from the physical sound signal has high necessity. In order to develop an estimation system of the direction of sound image corresponding to the multiple sound sources, it is necessary to know the behavior of the precedence effect in comprehensive sound source arrangement. So, we investigated the influence of the sound source arrangement on the precedence effect experimentally. The minimum angle between the directions of two sound sources is 30 degrees. Experimental method is a three Alternative Forced Choice Task. The three choices are in the direction of two sound sources and its intermediate. In the case of a bilaterally symmetrical arrangement of sound sources, our experimental results were in good agreement with the findings obtained in previous studies. However, our experimental results show that deviation of the localized direction of sound image is dependent on the sound image arrangement. Particularly, in the case of l...

Disrupted latent decision processes in medication-free pediatric OCD patients

BackgroundDecision-making in Obsessive Compulsive Disorder has typically been investigated in the adult population. Computational approaches have recently started to get integrated into these studies. However, decision-making research in pediatric OCD populations is scarce. MethodsWe investigated latent decision processes in 21 medication-free pediatric OCD patients and 23 healthy control participants. We hypothesized that OCD patients would be more cautious and less efficient in evidence accumulation than controls in a two alternative forced choice (2AFC) task. ResultsPediatric OCD patients were less efficient than controls in accumulating perceptual evidence and showed a tendency to be more cautious. In comparison to post-correct decisions, OCD patients increased decision thresholds after erroneous decisions, whereas healthy controls decreased decision thresholds. These changes were coupled with weaker evidence accumulation after errors in both groups. LimitationsThe small sample size limited the power of the study. ConclusionsOur results demonstrate poorer decision-making performance in pediatric OCD patients at the level of latent processes, specifically in terms of evidence accumulation.