This study examined whether the sensitivity of detecting emotions in noisy speech (acoustic) signals differed in healthy individuals and if their inter-individual differences of internal states (trait and state anxiety) influenced their respective emotion detection sensitivities. We collected the data in a more ecologically valid, natural environment of the participants' own accommodations. Consequently, we found that not only did the detection sensitivities vary across emotion signals, but also the subjective severities of only trait but not state-anxiety in the individuals compromised the average detection sensitivities across emotions, particularly of the negative emotions (Disgust and Fear). In sum, the findings suggest that dispositional trait of anxiety in individuals may influence the auditory appraisal of vocal emotions in noise-ridden natural environments.
Existing in-laboratory studies have shown that various aspects of an organism's internal state influence auditory functions in both animals 15,16 and humans 17–20. Of the human studies, it has been evident that internal states, e.g. anxiety and emotional arousal impact auditory perception auditory perception 17,18; evoked potentials 19 and perceptual categorization of everyday sounds. Our findings supplement these works in evidencing that internal state, e.g. trait-anxiety, also influences the correct detection of vocal emotions corrupted by background noise, and that it extends beyond a controlled laboratory environment.
Anxiety is an apprehension about an impending threat without any sound rationale and is characterized by nervousness, worry and activation of the autonomic nervous system (arousal). Trait anxiety is a relatively stable disposition of an individual personality that predisposes one to evaluate a range of otherwise innocuous events as potentially threatening, and this individual difference in anxiety proneness is indexed by the trait subscale of the STAI. By contrast, the state subscale of the STAI indexes the aforesaid characteristics of subjective anxiety at the given moment of administering the instrument 29,34,35. Findings from the visual sensory modality show the various biases to visual function on account of anxiety but more importantly, point to a close link between anxiety and processing of environmental affective information (e.g. emotions), which may have a bearing on the visual functions 4,12–14,36,37. Along these lines, reports of clear association between anxiety and affective processing, e.g., detection of emotions from acoustic signals in humans, have been scarce in the literature, to our knowledge. Our study thus, fills in this gap by furnishing evidence that the findings with visual sensory modality are mirrored with the auditory modality as well. As we focus on the dimensional representation of anxiety on a continuum in a healthy sample and its association with an objectively quantifiable aspect of auditory behaviour, the findings may extend our understanding of dysregulated behaviour in affective disorders. This is particularly relevant since the extant literature suggests varying degrees of anomalous auditory processing of stimuli in individuals with affective disorders, e.g. schizophrenia 38 and depression 39, which in turn have been associated with distinct neural correlates in the auditory cortex in humans 40.
Auditory perception of speech proceeds through a number of feature extraction steps at different stages of neural processing, involving a dynamic cross-talk between bottom-up (sensory-driven) and top-down (experience/context driven) processes in the brain41. There have been reports of the contribution of prior experience/context driven processes in facilitating auditory neurons in filtering out noise from taskrelevant acoustic signals at any given moment, towards processing auditory information 42–44. It is thus plausible, that in our experiment, the subjective behavioural context (e.g., anxiety, arousal) was also a key factor in modulating the efficiency of filtering negative affective speech signals (Disgust and Fear) out of white background noise, thereby influencing the auditory sensory gain and ultimately auditory emotion. There have been reports of the contribution of prior experience/context driven processes in facilitating auditory neurons in filtering out noise from task-relevant acoustic signals at any given moment, towards processing auditory information 42–44. It is thus plausible, that in our experiment, the subjective behavioural context (e.g., anxiety, arousal) was also a key factor in modulating the efficiency of filtering negative affective speech signals (Disgust and Fear) out of background white noise, thereby influencing the auditory sensory gain and ultimately auditory emotion perception as reflected by the correlations in our results. The fact that the effects in our data were observed with predominantly negative, threatening affective signals (Disgust and Fear) could be explained on the premise that such environmental stimuli are processed faster and with more efficiency in the brain towards influencing behaviour 45. These conclusions from our results advance the findings of a recent study that also points at different induced moods influencing masked auditory detection thresholds in humans, but somehow, their data did not allow drawing unequivocal conclusions 46.
Our findings of progressive decrements in auditory emotion detection sensitivity with increasing anxiety is in contrast to earlier reports of enhancements in visual sensitivity with anxiety 47–49. It is, thus, possible that the effect anxiety has on the detection sensitivity of certain environmental stimuli varies between visual and auditory sensitivity, which merits further enquiry. Finally, our findings may gain more credence if the replication of our results are also replicated in a larger sample and in a controlled laboratory environment.