Rule-based and stimulus-based cues bias auditory decisions via different computational and physiological mechanisms

The varied effects of expectations on auditory perception are not well understood. For example, both top-down rules and bottom-up stimulus regularities generate expectations that can bias subsequent perceptual judgments. However, it is unknown whether these different sources of bias use the same or different computational and physiological mechanisms. We examined how rule-based and stimulus-based expectations influenced human subjects’ behavior and pupil-linked arousal, a marker of certain forms of expectation-based processing, during an auditory frequency-discrimination task. Rule-based cues biased choice and response times (RTs) toward the more-probable stimulus. In contrast, stimulus-based cues had a complex combination of effects, including choice and RT biases toward and away from the frequency of recently heard stimuli. These different behavioral patterns also had distinct computational signatures, including different modulations of key components of a novel form of a drift-diffusion model, and distinct physiological signatures, including substantial bias-dependent modulations of pupil size in response to rule-based but not stimulus-based cues. These results imply that different sources of expectations can modulate auditory perception via distinct mechanisms: one that uses arousal-linked, rule-based information and another that uses arousal-independent, stimulus-based information to bias the speed and accuracy of auditory perceptual decisions.

Optimal Dyadic Integration of Complementary Perceptual Judgments Under Condition of Prescribed Agreement

We investigated whether prescribing an agreement can result in optimal inter-individual integration of perceptual judgments in absence of verbal communication. Participants in pairs performed a localization task in a virtual 3D environment, where the goal was to make projections from an upper plane to the target on the bottom plane. Partners were provided with complementary viewpoints and could be optimal if each took over one orthogonal dimension. In the Revision condition partners saw each other’s individual judgments and could rely on them. In the Agreement condition they provided a joint response. In both conditions communication was not allowed. We found that participants could optimally distribute the dimensions, but only when agreement was mandated. Without the agreement requirement, participants failed to properly rely on their partner on the dimension where the latter were more accurate. We also found, that prescription of agreement exerts a general positive effect on individual performance.Our results demonstrate that even in absence of verbal communication, interacting in a shared environment can result in optimal integration of perceptual information under the condition that an agreement is reached.

Perceptual judgments for the softness of materials under indentation

Humans can judge the softness of elastic materials through only visual cues. However, factors contributing to the judgement of visual softness are not yet fully understood. We conducted a psychophysical experiment to determine which factors and motion features contribute to the apparent softness of materials. Observers watched video clips in which materials were indented from the top surface to a certain depth, and reported the apparent softness of the materials. The depth and speed of indentation were systematically manipulated. As physical characteristics of materials, compliance was also controlled. It was found that higher indentation speeds resulted in larger softness rating scores and the variation with the indentation speed was successfully explained by the image motion speed. The indentation depth had a powerful effect on the softness rating scores whose variation with the indentation depth was consistently explained by motion features related to overall deformation. Higher material compliance resulted in higher rating scores while their effect was not straightforwardly explained by the motion features. We conclude that the brain makes visual judgments about the softness of materials under indentation on the basis of the motion speed and deformation magnitude while motion features related to material compliance require further study.

Serial dependence in the perceptual judgments of radiologists

In radiological screening, clinicians scan myriads of radiographs with the intent of recognizing and differentiating lesions. Even though they are trained experts, radiologists’ human search engines are not perfect: average daily error rates are estimated around 3–5%. A main underlying assumption in radiological screening is that visual search on a current radiograph occurs independently of previously seen radiographs. However, recent studies have shown that human perception is biased by previously seen stimuli; the bias in our visual system to misperceive current stimuli towards previous stimuli is called serial dependence. Here, we tested whether serial dependence impacts radiologists’ recognition of simulated lesions embedded in actual radiographs. We found that serial dependence affected radiologists’ recognition of simulated lesions; perception on an average trial was pulled 13% toward the 1-back stimulus. Simulated lesions were perceived as biased towards the those seen in the previous 1 or 2 radiographs. Similar results were found when testing lesion recognition in a group of untrained observers. Taken together, these results suggest that perceptual judgements of radiologists are affected by previous visual experience, and thus some of the diagnostic errors exhibited by radiologists may be caused by serial dependence from previously seen radiographs.

Neighborhood-Based Information Costs

We derive a new cost of information in rational inattention problems, the neighborhood-based cost functions, starting from the observation that many settings involve exogenous states with a topological structure. These cost functions are uniformly posterior separable and capture notions of perceptual distance. This second property ensures that neighborhood-based costs, unlike mutual information, make accurate predictions about behavior in perceptual experiments. We compare the implications of our neighborhood-based cost functions with those of the mutual information in a series of applications: perceptual judgments, the general environment of binary choice, regime-change games, and linear-quadratic-Gaussian settings. (JEL C70, D11, D82, D83, D91)

Pupil-Linked Arousal Biases Evidence Accumulation Toward Desirable Percepts During Perceptual Decision-Making

People’s perceptual reports are biased toward percepts they are motivated to see. The arousal system coordinates the body’s response to motivationally significant events and is well positioned to regulate motivational effects on perceptual judgments. However, it remains unclear whether arousal would enhance or reduce motivational biases. Here, we measured pupil dilation as a measure of arousal while participants ( N = 38) performed a visual categorization task. We used monetary bonuses to motivate participants to perceive one category over another. Even though the reward-maximizing strategy was to perform the task accurately, participants were more likely to report seeing the desirable category. Furthermore, higher arousal levels were associated with making motivationally biased responses. Analyses using computational models suggested that arousal enhanced motivational effects by biasing evidence accumulation in favor of desirable percepts. These results suggest that heightened arousal biases people toward what they want to see and away from an objective representation of the environment.

Smartphone display size can influence perceptual judgments

Classic research in perception has suggested that visual context can impact how individuals perceive object characteristics like physical size. The current set of studies extends this work to an applied setting by examining whether smartphone display size can impact the perception of objects presented on smartphones. Participants viewed several target items, on two different sized virtual device displays based on actual consumer devices and were asked to make simple judgments of the size of presented objects. Results from both experiments confirm that display size impacts perceived size, such that larger displays cause users to significantly underestimate the size of objects moreso than smaller displays. This is the first study to confirm such an effect, and suggests that beyond aesthetics or cost, one’s personal choice of device might have additional performance consequences.

ACOUSTIC EFFECTS OF DURATIONAL CUES IN THE PERCEPTION OF NAJDI ARABIC VOWEL CONTINUA

This paper explores how the manipulation of vowel duration as a perceptual cue influences listeners’ perceptual ability. Four native speakers of Najdi Arabic, a well-known variety of Arabic in the Arabian Peninsula, were tested on the perception of /a/ vs. /ɛ/ vowels. Listeners’ identification and discrimination rates along each vowel continuum showed a clear effect of duration on the perception of /a/-/ɛ/ contrast. In each vowel continuum, listeners were more inclined to classify stimuli as belonging to one vowel or the other based on relative proximity to the steady-state vowel duration. Perceptibility naturally improved as duration approximated the normal duration of either vowel. Listeners’ perceptual judgments in the identification and discrimination of the vowels were swayed by their aural sensitivity to perceptual shifts (/a/-/ɛ/ at 185-195ms; /ɛ/-/a/ at 195-205ms). Moreover, findings of the identification task followed predictably from the discrimination task; this could be taken as evidence for the existence of categorical perception. Results aggregately indicate that perception of the two Najdi Arabic vowels proceeded as a function of duration.

Perception during use of force and the likelihood of firing upon an unarmed person

Stress can impact perception, especially during use-of-force. Research efforts can thus advance both theory and practice by examining how perception during use-of-force might drive behavior. The current study explored the relationship between perceptual judgments and performance during novel close-combat training. Analyses included perceptual judgments from close-combat assessments conducted pre-training and post-training that required realistic use-of-force decisions in addition to an artificially construed stress-inoculation event used as a training exercise. Participants demonstrated significant reductions in situational awareness while under direct fire, which correlated to increased physiological stress. The initial likelihood of firing upon an unarmed person predicted the perceptual shortcomings of later stress-inoculation training. Subsequently, likelihood of firing upon an unarmed person was reduced following the stress-inoculation training. These preliminary findings have several implications for low or zero-cost solutions that might help trainers identify individuals who are underprepared for field responsibilities.

Colors and Handles: How Action Primes Perception

How deeply does action influence perception? Does action performance affect the perception of object features directly related to action only? Or does it concern also object features such as colors, which are not held to directly afford action? The present study aimed at answering these questions. We asked participants to repeatedly grasp a handled mug hidden from their view before judging whether a visually presented mug was blue rather than cyan. The motor training impacted on their perceptual judgments, by speeding participants’ responses, when the handle of the presented mug was spatially aligned with the trained hand. The priming effect did not occur when participants were trained to merely touch the mug with their hand closed in a fist. This indicates that action performance may shape the perceptual judgment on object features, even when these features are colors and do not afford any action. How we act on surrounding objects is therefore not without consequence for how we experience them.