Decoding odor responses: universal patterns and individual signatures in psychophysiology using nonlinear models

When designing multisensorial experiences, robustly predicting the crossmodal perception of olfactory stimuli is a critical factor. We investigate the possibility of predicting olfactory crossmodal correspondences using the underlying physicochemical features. An electronic nose was tuned to the crossmodal perceptual axis of olfaction and was used to foretell people's crossmodal correspondences between odors and the angularity of shapes, smoothness of texture, perceived pleasantness, pitch, and colors. We found that the underlying physicochemical features of odors could be used to predict people's crossmodal correspondences. The human-machine perceptual dimensions that correlated well are the angularity of shapes (r = 0.71), the smoothness of texture (r = 0.82), pitch (r = 0.70), and the lightness of color (r = 0.59). The human-machine perceptual dimensions that did not correlate well (r < 0.50) are the perceived pleasantness (r = 0.20) and the hue of the color (r = 0.42 & 0.44). All perceptual dimensions except for the perceived pleasantness could be robustly predicted (p-values < 0.0001) including the hue of color. While it is recognized that olfactory perception is strongly shaped by learning and experience, our findings suggest that there is a systematic and predictable link between the physicochemical features of odorous stimuli and crossmodal correspondences. These findings may provide a crucial building block towards the digital transmission of smell and enhancing multisensorial experiences with better designs as well as more engaging, and enriched experiences.

Patterns of psychophysiological and acoustic responses and flat affect in schizophrenia

The purpose of this study was to determine the effect of video presentation on perceptual dimensions in perceiving Asian musics and on preferences for Asian musics. Asian musics comprised 15 musical excerpts selected from a video anthology. Forty-nine undergraduate non-music majors were randomly assigned to receive video-audio stimuli or audio-only stimuli. The author analysed the data using Multidimensional Scaling (MDS) techniques. A three-dimensional solution was found for each group (video group and audio group). The first dimension of both groups shared 83 83% of variance (stimulus characteristics and preference). Dimension 3 of the video group and Dimension 2 of the audio group shared 6139% of variance (danceability and preference). However, Dimension 2 of the video group (active visible movement and setting) and Dimension 3 of the audio group (undetermined) were unique in that they did not share significant variance with any dimension of the other group. In addition, geographic region did not help interpret any of the perceptual dimensions in either group. Implications of this study are that teachers who use video stimuli should be aware of visual qualities as well as musical characteristics. Teachers may use both video and audio materials in classes to enrich students' musical experience. Teachers should be cautious when organising an Asian music curriculum according to geographic region.

This paper presents the analysis of four psychophysiological responses in post-stroke upper extremity rehabilitation. The goal was to determine which psychophysiological responses would provide the most reliable information about subjects' psychological states during rehabilitation. Heart rate, skin conductance, respiration, and skin temperature were recorded in a stroke group and a control group during two difficulty levels of a pick-and-place task performed in a virtual environment using a haptic robot and during a cognitive task. Psychophysiological measurements were correlated with results of a self-report questionnaire. All four responses showed significant changes in response to the different tasks. Skin conductance differentiated between the two difficulty levels and was correlated with self-reported arousal in both stroke and control groups. Skin temperature differentiated between the two difficulty levels for the control group, but provided poor results for the stroke group. Heart rate and respiration increased during tasks, but their connection to psychological state was unclear. Results suggest that, of the four measured responses, skin conductance offers the most potential as a psychological state indicator, with other measures providing supplementary information. Psychophysiological measurements could thus be used in closed-loop biocooperative systems that would detect the user's psychological state and change the course of therapy accordingly.

Although the sense of smell in pigs is widely recognized as being highly developed, surprisingly little is known about their sensory ability. This study aimed to (a) identify which non-social odors pigs were able to detect and distinguish between, (b) investigate the types of behavior expressed when exploring odors and, (c) compare pigs' responses to the different odors to evaluate their interest in the odors. Growing pigs (N = 192) of crossbred commercial breeds were enrolled in the experiment (32-110 days of age, weighing 64.9 ± 10.1kg). Littermate pairs of opposite sex were tested in test pens with two odor insertion points in the pen wall, 55 cm apart. All pigs were habituated to the test pens and experimenters. Twelve odors were tested (eight essential oils and four synthetic perfumes) in groups of three odors, with each pig pair tested once with one set of three odors (all possible orders of the three odors were tested on 24 pairs in total), always against a non-odor control (demineralized water). In a test, each of the three odors were presented during three trials in a row (a total of 9 trials per test; trial duration: 1 min; inter-trial breaks: 2 min; total test duration: 25 min). Response variables included: duration of sniffing, feeding-related behavior (licking, biting and rooting), agonistic behavior (biting, displacement and pushing) and no approach of the odor or control, recorded throughout each 1-min odor presentation. All pigs sniffed an odor less when repeatedly presented (LMM: all odors P < 0.05), and significantly longer at the subsequent presentation of a new odor [LMM (3rd vs. 1st presentations): P < 0.001]. Specific odor and odor type (essential oil vs. synthetic perfume) had no significant effect on sniffing duration. Overall, feeding-related behavior and agonistic behavior were expressed significantly more when pigs explored the odor compared with the control insertion point (Paired t-tests: P < 0.001), and specific odor only affected the expression of feeding-related behavior. Collectively, pigs express sniffing, agonistic, and feeding-related behavior when exploring odors, which suggests that pigs perceive odors of non-social origin as a resource. Odors may thus constitute relevant enrichment material for pigs.

The relationship between similarity judgments and psychophysiological responsivity

The effects of noise and other competing backgrounds on speech recognition performance are well documented. There is less information, however, on listening effort and stress experienced by listeners during a speech-recognition task that requires inhibition of competing sounds. The purpose was (a) to determine if psychophysiological indexes of listening effort were more sensitive than performance measures (percentage correct) obtained near ceiling level during a competing speech task, (b) to determine the relative sensitivity of four psychophysiological measures to changes in task demand, and (c) to determine the relationships between changes in psychophysiological measures and changes in subjective ratings of stress and workload. A repeated-measures experimental design was used to examine changes in performance, psychophysiological measures, and subjective ratings in response to increasing task demand. Fifteen adults with normal hearing participated in the study. The mean age of the participants was 27 (range: 24-54). Psychophysiological recordings of heart rate, skin conductance, skin temperature, and electromyographic (EMG) activity were obtained during listening tasks of varying demand. Materials from the Dichotic Digits Test were used to modulate task demand. The three levels of task demand were single digits presented to one ear (low-demand reference condition), single digits presented simultaneously to both ears (medium demand), and a series of two digits presented simultaneously to both ears (high demand). Participants were asked to repeat all the digits they heard, while psychophysiological activity was recorded simultaneously. Subjective ratings of task load were obtained after each condition using the National Aeronautics and Space Administration Task Load Index questionnaire. Repeated-measures analyses of variance were completed for each measure using task demand and session as factors. Mean performance was higher than 96% for all listening tasks. There was no significant change in performance across listening conditions for any listener. There was, however, a significant increase in mean skin conductance and EMG activity as task demand increased. Heart rate and skin temperature did not change significantly. There was no strong association between subjective and psychophysiological measures, but all participants with mean normalized effort ratings of greater than 4.5 (i.e., effort increased by a factor of at least 4.5) showed significant changes in skin conductance. Even in the absence of substantial performance changes, listeners may experience changes in subjective and psychophysiological responses consistent with the activation of a stress response. Skin conductance appears to be the most promising measure for evaluating individual changes in psychophysiological responses during listening tasks.

Psychophysiological responses have been studied as objective indicators for measuring a learner’s cognitive load. Previous studies have correlated pupil dilation or fixation length with increased cognitive load. Our aims were to confirm whether these findings could be applied in a general learning context and to verify the additivity hypothesis of cognitive load theory based on psychophysiological responses. Three responses (i.e., mean pupil diameter, area under the pupil response curve, and sum of fixation duration) were recorded while 94 participants completed a computer-based test. Participants were randomly assigned to low (n = 46) or high (n = 48) extraneous cognitive load conditions. Because the given test, which consisted of a low and a high task complexity problem, was the same for all participants, the difference in intrinsic cognitive load was compared as a within-subjects factor. Each psychophysiological indicator was calculated and compared under different intrinsic and extraneous cognitive load conditions. The results showed that psychophysiological responses significantly distinguished the differences in intrinsic and extraneous cognitive loads. In addition, the sum of the different types of cognitive loads corresponded to the total cognitive load. Based on the results, further studies are suggested to apply psychophysiological responses as the standard of judgment for different levels of cognitive load.

Morality has been an integral part of social cognition and our daily life, and different languages may exert distinct impacts on human moral judgment. However, it remains unclear how moral concept is encoded in the bilingual brain. This study, therefore, aimed to explore the emotional and cognitive involvement of bilingual morality judgement by using combined event-related potential (ERP) and psychophysiological (including skin, heart, and pulse) measures. In the experiment, thirty-one Chinese–English bilingual participants were asked to make moral judgments in Chinese and English, respectively. Our results revealed increased early frontal N400 and decreased LPC in L1 moral concept encoding as compared to L2, suggesting that L1 was more reliant on automatic processes and emotions yet less on elaboration. In contrast, L2 moral and immoral concepts elicited enhanced LPC, decreased N400, and greater automatic psychophysiological electrocardiograph responses, which might reflect more elaborate processing despite blunted emotional responses and increased anxiety. Additionally, both behavioral and P200 data revealed a reliable immorality bias across languages. Our results were discussed in light of the dual-process framework of moral judgments and the (dis)embodiment of bilingual processing, which may advance our understanding of the interplay between language and morality as well as between emotion and cognition.

Increasing automation and the rapidly growing use of robots in industrial as well as social areas result in a greater need for research regarding collaboration between humans and robots. Key factors for a safe and successful combination of human and robot abilities include acceptance and trust in the robot. In order to prevent physical and psychological harm to humans, reducing these negative emotions and increasing trust and acceptance are essential. One way to achieve this is through the use of virtual training methods and environments. However, current research scarcely covers this approach. Therefore, this research focusses on an experimental approach to investigate emotional and psychophysiological (ECG, EDA) reactions while performing a collaborative assembly task (screwing) with an industrial robot in a real and a virtual setting, respectively. The study sample consisted of 46 participants (23 female) with an age range from 20 to 58 years. The results of the analyzed subjective and objective psychophysiological (cardiovascular and electrodermal responses) measures provide more information regarding the suitability of virtual trainings for human–robot collaboration. Differences in task complexity were measurable in both virtual and real environments. Furthermore, gender differences were also shown.

Psychophysiological reactivity of currently dental phobic-, remitted dental phobic- and never-dental phobic individuals during exposure to dental-related and other affect-inducing materials

Introduction: Aging has been associated with a decline in cognitive and motor performance, often expressed in multitasking situations, which could include wayfinding. A major challenge to successful wayfinding is spatial disorientation, occurring mostly at crossings. Although gait changes have been observed in various dual-task conditions, little is known about the effect of disorientation on gait and psychophysiological response among older adults during wayfinding. The study aimed at identifying the effect of spatial disorientation on gait variability and psychophysiological response among healthy older adults during wayfinding in a controlled environment. Method: We analyzed data of 28 participants (age 70.8 ± 4.6, 18 female), 14 experimental and 14 controls. Participants performed a wayfinding task consisting of 14 major decision points (7 intersections) within a virtual environment (VE) projected on a 180° screen while walking on a self-paced treadmill equipped with a marker-based optical motion-capture system. The VE was held constant for the controls and manipulated for the experimental participants. Disorientation was identified based on a customized annotation scheme. Variability in gait, including the coefficient of variation (CV), was measured as the primary endpoint. Psychophysiological response measures, including heart rate variability (RMSSD) and skin conductance response (SCR), were continuously monitored as secondary endpoints and estimates of cognitive effort. Linear Mixed Effects models were applied to hypothesis-driven outcome measures extracted from decision points. Results: Walking speed and step length decreased when disoriented (p < 0.05), while stride time, stance time, walking speed CV, stance time CV, SCR amplitude, and SCR count increased when disoriented (p < 0.05). A higher RMSSD was associated with being disoriented at crossings (p < 0.05). SCR count was greater in the older experimental group (p < 0.001), including when disoriented (p < 0.001). Discussion/Conclusion: The results provide evidence for the impact of spatial disorientation on changes in gait pattern and psychophysiological response among older adults during wayfinding. Location also had implications for the effect of disorientation on gait and cognitive effort. This gives further insight into the substrates of real-world navigation challenges among older adults, with an emphasis on viable features for designing situation-adaptive interventional devices aiding independent mobility.

The present study focuses on the relation between stimulus features and psychophysiological responsivity by using a modified version of the information detection paradigm. Compound pictorial and verbal stimuli (schematic faces with beard, glasses, and hat, and descriptions of people in terms of occupation, city of residence, a hobby, and a personality trait) were used as the relevant stimuli that subjects were instructed to memorize. Skin conductance responses were measured during the subsequent presentation of a sequence of test stimuli. Each sequence included a critical stimulus that shared from one to four common components with the relevant stimulus in each of two pictorial and two verbal experiments. We hypothesized that the electrodermal responsivity to the critical stimulus would reflect the degree it matches the relevant one. The results indicated that when the critical stimulus was identical to the relevant stimulus, responsivity was maximal. Neutral stimuli (i.e., those that shared no components with the relevant stimulus) produced minimal responsivity, and critical stimuli that only partially matched the relevant one produced intermediate levels of responsivity (in spite of the subjects' awareness of the differences between the critical and the relevant stimuli). The monotonic relation between the degree of match and responsivity supports the proposed model, which assumes that each stimulus in the sequence is being compared with the relevant stimulus by a feature-matching process, and electrodermal responsivity is related to the outcome of this process. In a fifth experiment, we compared geometric and contrast models for similarity and found that the pattern of responsivity violated the minimality and symmetry assumptions of the geometric model. The relation between cognitive processes and psychophysiological responsivity is discussed, as are implications for the application of the guilty knowledge technique for detecting information.

polyphonic timbre perception was investigated in a cross-cultural context wherein Indian and Western nonmusicians rated short Indian and Western popular music excerpts (1.5 s, n = 200) on eight bipolar scales. Intrinsic dimensionality estimation revealed a higher number of perceptual dimensions in the timbre space for music from one's own culture. Factor analyses of Indian and Western participants' ratings resulted in highly similar factor solutions. The acoustic features that predicted the perceptual dimensions were similar across the two participant groups. Furthermore, both the perceptual dimensions and their acoustic correlates matched closely with the results of a previous study performed using Western musicians as participants. Regression analyses revealed relatively well performing models for the perceptual dimensions. The models displayed relatively high cross-validation performance. The findings suggest the presence of universal patterns in polyphonic timbre perception while demonstrating the increase of dimensionality of timbre space as a result of enculturation.

Research on specific qualities of music used for relaxation has shown conflicting results. The use of different familiar or pre-composed pieces, with many simultaneous changes, might limit the ability to discriminate which musical element is responsible for the relaxation response. To address the latter, we examined the relaxing effects of music on three psychophysiological measures (heart rate, respiration rate, and skin conductance) with one original piece of music, and three modified versions (altering one musical element in each version). We investigated whether participants’ psychophysiological responses reflected a more “relaxed” state (lower heart rate, respiration rate, and skin conductance) with slower tempo (45 bpm), mellow timbre (bass clarinet), or smaller amplitude (-10 dB). We also investigated whether psychophysiological responses were consistent with self-report scores. Visual inspection of psychophysiological data indicated two distinct responder profiles, and a logistic regression confirmed this distinction. Using mixed ANCOVAs, we found significant differences between participants (responders and non-responders) in skin conductance level. No correlations between psychophysiological measures and self-reports were found. These findings raise interesting questions regarding the mechanisms behind the relaxing effects of music.