This cross-sectional, observational study focused on examining sex differences in auditory saliency judgments to evaluate sex differences in the bottom-up auditory attention. We found that males and females differ in their auditory saliency judgments and that females’ saliency judgments are influenced by loudness.
Previous studies on auditory saliency judgments have focused on the relationship between auditory saliency and acoustic features, such as the relationship between bottom-up and top-down auditory attention distinctions, but they have not examined sex differences [9–11]. To our knowledge, the present study is the first to show sex differences in auditory saliency judgments. According to our results, sex differences in auditory saliency judgments differed depending on the token of the sound event. Males had significantly higher agreement in their responses to FT with salience semantic attributes, whereas females had significantly higher agreement in their responses to BT without salience semantic attributes. The sound events that generated more intersubject agreement were those responses to which bottom-up auditory attention significantly contributed [9]. In other words, males’ auditory saliency judgments based on bottom-up auditory attention are influenced by the semantic attributes of the sound salience, whereas females’ auditory saliency judgments are influenced by other factors. These findings could be explained by the following two points. First, auditory processing is predominantly female in animals and humans [20]. In particular, in humans, females have better auditory thresholds [15, 16], sound-harmonics processing [21], and emotional signal processing [22] than males; thus, females may have been more sensitive to acoustical features than males. Second, these auditory findings are consistent with many research findings in the visual area. In visual spatial attention tasks, females attend to various stimuli and use more attentional resources than males [7, 8]. Likewise, females may attend to various stimuli than males in auditory attention.
Regarding the relationship between auditory saliency and loudness by sex, we found that females are more likely to be influenced by loudness in judging saliency than males. The relationship between auditory saliency and acoustic features has already been investigated [9–13], with particular emphasis on the relationship between loudness and auditory saliency [14]. However, sex differences in loudness and auditory prominence remain unexamined. Our study results showed that females were more influenced by loudness in making saliency judgments than males; thus, females make more saliency judgments for various sound events. This factor is controversial because the relationship between the acoustical characteristics of stimuli and qualitative factors in sex differences in auditory saliency judgments is still insufficiently reported; therefore, the sex differences in loudness and auditory saliency remain controversial.
In addition, we evaluated auditory saliency by behavioral measures based on participants' subjective self-assessments. Measures of auditory saliency in most studies have been pupil dilation responses [12–14]. However, pupil dilation responses do not necessarily correspond to auditory saliency, and auditory saliency evaluation requires more continuous and active scene scanning by the participants [10]. Therefore, we evaluated auditory saliency by using a participant’s manual annotation of sound events task in response to a 1-minute audio stimulus. Participants’ manual annotation of objects is a common task [23, 24], but it can be influenced by top-down attention. Nevertheless, this disadvantage can be counteracted by adjusting the results according to the consistency of responses across numerous participants [10, 11]. The present study aimed to distinguish between bottom-up and top-down auditory attention by using a behavioral paradigm that minimizes the contribution of top-down auditory attention. Although research on auditory attention is still in its infancy [25], the sex differences shown in our study seem to be consistent with trends in research in the visual area. Future research in the auditory area is encouraged.
This study has several limitations. First, the acoustic analysis of audio stimuli was evaluated using only duration, maximum loudness, and maximum spectrum. Therefore, the results can only be generalized to sex differences in some acoustic features and auditory saliency judgments. Further acoustic analyses are necessary to identify sex differences in bottom-up auditory attention. Second, this study showed that females’ auditory saliency judgments are related to loudness, but the causal effect of acoustic features influencing males’ auditory saliency judgments was not examined. Third, only young healthy adults were enrolled. Therefore, our findings are generalizable only to young adults without hearing or attention impairment. In addition, the relationship between sex differences in auditory saliency judgments and acoustic features in old adults and patients with hearing or attention impairment remains unclear. Finally, functional brain measures that can be used to evaluate bottom-up auditory attention were not performed. Further research, including functional brain measures, is needed to clarify sex differences in bottom-up auditory attention.