4,278 research outputs found
Automatic Stress Classification With Pupil Diameter Analysis
This article proposes a method based on wavelet transform and neural networks for relating pupillary behavior to psychological stress. The proposed method was tested by recording pupil diameter and electrodermal activity during a simulated driving task. Self-report measures were also collected. Participants performed a baseline run with the driving task only, followed by three stress runs where they were required to perform the driving task along with sound alerts, the presence of two human evaluators, and both. Self-reports and pupil diameter successfully indexed stress manipulation, and significant correlations were found between these measures. However, electrodermal activity did not vary accordingly. After training, the four-way parallel neural network classifier could guess whether a given unknown pupil diameter signal came from one of the four experimental trials with 79.2% precision. The present study shows that pupil diameter signal has good discriminating power for stress detection
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Macaques preferentially attend to visual patterns with higher fractal dimension contours.
Animals' sensory systems evolved to efficiently process information from their environmental niches. Niches often include irregular shapes and rough textures (e.g., jagged terrain, canopy outlines) that must be navigated to find food, escape predators, and master other fitness-related challenges. For most primates, vision is the dominant sensory modality and thus, primates have evolved systems for processing complicated visual stimuli. One way to quantify information present in visual stimuli in natural scenes is evaluating their fractal dimension. We hypothesized that sensitivity to complicated geometric forms, indexed by fractal dimension, is an evolutionarily conserved capacity, and tested this capacity in rhesus macaques (Macaca mulatta). Monkeys viewed paired black and white images of simulated self-similar contours that systematically varied in fractal dimension while their attention to the stimuli was measured using noninvasive infrared eye tracking. They fixated more frequently on, dwelled for longer durations on, and had attentional biases towards images that contain boundary contours with higher fractal dimensions. This indicates that, like humans, they discriminate between visual stimuli on the basis of fractal dimension and may prefer viewing informationally rich visual stimuli. Our findings suggest that sensitivity to fractal dimension may be a wider ability of the vertebrate vision system
Pupil response as an indicator of hazard perception during simulator driving
We investigate the pupil response to hazard perception during driving simulation. Complementary to gaze movement and physiological stress indicators, pupil size changes can provide valuable information on traffic hazard perception with a relatively low temporal delay. We tackle the challenge of identifying those pupil dilation events associated with hazardous events from a noisy signal by a combination of wavelet transformation and machine learning. Therefore, we use features of the wavelet components as training data of a support vector machine. We further demonstrate how to utilize the method for the analysis of actual hazard perception and how it may differ from the behavioral driving response
Computational Psychiatry and Psychometrics Based on Non-Conscious Stimuli Input and Pupil Response Output
It is well known from the technical literature that non-conscious perception of emotional stimuli
affects behavior, perception, and even decision making [e.g., see Ref. (1) for a comprehensive
review]. Non-conscious perception can be obtained by inducing sensory unawareness, e.g., through
backward masking and binocular rivalry (1). Experiments adopting such paradigms have evidenced
that non-consciously perceived emotional stimuli elicit activity in the amygdala, superior colliculus,
basal ganglia, and pulvinar. More specifically, it has been shown that a subcortical fast route exists
between the thalamus and the amygdala, which, in turn, project onto different cortical and subcortical
structures [e.g., onto the nucleus accumbens, NAcc, when appetitive stimuli are perceived (2)].
These findings agree with the hypothesis about amygdala functionality proposed by LeDoux (3, 4).
In fact, LeDoux has hypothized the existence of a thalamic pathway to the amygdala; such a pathway
would allow to automatically detect evolutionary prepared visual stimuli (such as emotional faces,
sexual-related stimuli, spiders, snakes, and injuries). Note that this model is also supported by other
results acquired by different researchers that have employed masking in normal participants (5, 6)
or have observed brain activity in patients affected by cortical blindness (7, 8). According to this
model about amygdala functionality, the superior colliculus stimulates the pulvinar nucleus of the
thalamus, which then arouses the amygdala (4, 9, 10). This suggests that salient features representing
biologically prepared stimuli could be stored in the amygdala since birth. From an evolutionary perspective,
this can be related to the fact that fast and implicit (or unconscious) reactions are needed in
dangerous and highly dynamical environments. Moreover, even ontogenetic stimuli (e.g., weapons)
are encoded within the amygdala through implicit learning during life (11, 12). These data evidence
the importance of subcortical regions associated with implicit emotional processing. In fact, since
the brain structure works like a hierarchical network (13) in which the limbic system represents a
lower hierarchical level with respect to the higher cortical structure, it is likely that the overall perception
and emotional appraisal are influenced by low-level evaluations. More specifically, the signals
coming from lower and higher hierarchical levels determine prediction errors (or error signals) at
intermediate levels; such error signals propagate through the entire hierarchical structure, determining
cognitive perception, causes attributions, emotional evaluations, actions, and behaviors (14).
Hence, if subcortical limbic-brainstem regions are defective, all the network hierarchy functioning
will be compromised. As a matter of fact, a dysfunction in the limbic-brainstem regions is associated
with various psychiatric disorders with higher cognitive deficits including autism, schizophrenia,
posttraumatic stress disorders (PTSD), attention deficits/hyperactivity disorder (ADHD), neurosis,
phobia, and others
ForDigitStress: A multi-modal stress dataset employing a digital job interview scenario
We present a multi-modal stress dataset that uses digital job interviews to
induce stress. The dataset provides multi-modal data of 40 participants
including audio, video (motion capturing, facial recognition, eye tracking) as
well as physiological information (photoplethysmography, electrodermal
activity). In addition to that, the dataset contains time-continuous
annotations for stress and occurred emotions (e.g. shame, anger, anxiety,
surprise). In order to establish a baseline, five different machine learning
classifiers (Support Vector Machine, K-Nearest Neighbors, Random Forest,
Long-Short-Term Memory Network) have been trained and evaluated on the proposed
dataset for a binary stress classification task. The best-performing classifier
achieved an accuracy of 88.3% and an F1-score of 87.5%
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