Mid Sweden University

The aim of this thesis was to investigate factors related to accuracy in estimation of speaker age and the role of certain speech properties in perception and manipulation of speaker age, as well as their interaction with the speech material that the age estimates were based on. This thesis consists of three studies.

In Study 1 the aim was to investigate the role of speech rate as well as the level of accuracy in estimation of speaker age, depending on linguistic variation in the speech material (read versus spontaneous speech). In two experiments, one using read speech from 36 female and male speakers in three age groups (younger: 20-25 years, middle aged: 40-45 years and older:60-65 years old) as stimuli, and the other using spontaneous speech from the same speakers, we investigated how changes in speech rate influenced listeners’ age estimates of young adult, middle aged and older speakers. The results revealed that listeners estimated the speakers as younger when speech rate was faster than normal and as older when speech rate was slower than normal. This speech rate effect was slightly greater in magnitude for older speakers in comparison with younger speakers, suggesting that speech rate may gain greater importance as a perceptual age cue with increased speaker age. This pattern was more pronounced in Experiment 2, in which listeners estimated age from spontaneous speech. Faster speech rate was associated with lower age estimates, but only for older and middle aged speakers. Taken together, speakers of all age groups were estimated as older when speech rate was decreased, except for the youngest speakers in Experiment 2. The absence of a linear speech rate effect in estimates of younger speakers, for spontaneous speech, implies that listeners use different age estimation strategies or cues (possibly vocabulary) depending on the age of the speaker and the spontaneity of the speech.

Study 2 investigated how speakers spontaneously manipulate two age related vocal characteristics (fundamental frequency and speech rate) in attempts to sound younger versus older than their true age, and if the manipulations correspond to actual age related changes in fundamental frequency (F0) and speech rate. The study also aimed at determining how successful vocal age disguise is by asking listeners to estimate the age of generated speech samples and to examine whether or not listeners use F0 and speech rate as cues to perceived age. Participants from three age groups (20–25, 40–45, and 60–65 years) agreed to read a short text under three voice conditions. There were 12 speakers in each age group (six women and six men). They used their natural voice in one condition, attempted to sound 20 years younger in another and 20 years older in a third condition. Sixty listeners were exposed to speech samples from the three voice conditions and estimated the speakers’ age. Each listener was exposed to all three voice conditions. The results indicated that the speakers increased F0 and speech rate when attempting to sound younger and decreased F0 and speech rate when attempting to sound older. The voice manipulations had an effect on age estimation in the sought-after direction, although the achieved mean effect was only 3 years, which is far less than the intended effect of 20 years. Moreover, listeners used speech rate, but not F0, as a cue to speaker age. It was concluded that age disguise by voice can be achieved by naïve speakers even though the perceived effect was smaller than intended.

In Study 3 the aim was to study confidence and accuracy in estimates of speaker age and whether confidence can serve as an indicator of estimation accuracy. Two experiments were performed investigating accuracy in estimation of speaker age, as well as the listeners’ confidence that their estimates were correct. In Experiment 1 listeners made age estimates based on spontaneous speech while in Experiment 2 the estimates were based on read speech. The purpose of the study was to explore differences in accuracy and confidence depending on speech material, speaker characteristics (gender and age) and listener gender. Another purpose was to examine the realism in the listeners’ confidence ratings in estimations of spontaneous versus read speech. No differences in accuracy or confidence were found due to speech material type. Although accuracy was higher in estimates of male speakers, confidence was higher in estimates of female speakers. As the correlation between confidence and accuracy was weak, it was concluded that confidence should not be relied on as an indicator of accuracy in estimation of speaker age.

The three studies in this thesis provide some insight into different aspects of perception of speaker age. Possible implications of the results and suggestions for further research are discussed.

The controversy over gender differences in exposure to domestic violence (DV) seems to be a never-ending story. Researchers on one side of the debate argue that men and women are equally victimized (gender symmetry), while researches on the other side of the debate argue that women are victimized to larger extent, and with greater severity (gender asymmetry). Evidence for gender symmetry is based mainly on quantitative data from a plentitude of surveys measuring gender differences in perpetration and exposure to intimate partner violence. The asymmetry perspective, on the other hand, emphasizes investigation of contextual factors (e.g. the impact and meaning of violence) but have been based on studies that to a lesser extent include both men and women. Hence, there are conceptual and methodological differences between studies that find gender symmetry and those that propose gender asymmetry. We will present a survey performed to measure the prevalence of exposure to DV among men and women in the municipality of Gävle, Sweden. The presentation will highlight the significance of coercive control, temporal aspects, and impact of violence in measurement and understanding of gender differences in exposure to DV. Results from the survey suggest that women had been more exposed than men to all types of violence measured (psychological, sexual, physical, economical-material, latent violence and negligence), that female exposure were more often repeated, and lead to more severe consequences than did male exposure to DV. We also found that having children with the perpetrator, which was more common among women, was a stronger predictor of negative consequences than any single type of violence. We will also present results concerning children of DV victims and experiences of help seeking and reporting violence.

The relationship between vocal characteristics and perceived age is of interest in various contexts, as is the possibility to affect age perception through vocal manipulation. A few examples of such situations are when age is staged by actors, when ear witnesses make age assessments based on vocal cues only or when offenders disguise their voice to appear younger or older. This paper investigates how speakers spontaneously manipulate two age related vocal characteristics (f0 and speech rate) in attempt to sound younger versus older than their true age, and if the manipulation corresponds to actual age related changes in f0 and speech rate (Study 1). Further aims of the paper is to determine how successful vocal age disguise is by asking listeners to estimate the age of generated speech samples (Study 2) and to examine whether or not listeners use f0 and speech rate as cues to perceived age. In Study 1, participants from three age groups (20-25, 40-45 and 60-65 years) agreed to read a short text under three voice conditions. There were 12 speakers in each age group (six women and six men). They used their natural voice in one condition, attempted to sound 20 years younger in another and 20 years older in a third condition. In Study 2, 60 participants (listeners) listened to speech samples from the three voice conditions in Study 1 and estimated the speakers’ age. Each listener was exposed to all three voice conditions. The results from Study 1 indicated that the speakers increased fundamental frequency (f0) and speech rate when attempting to sound younger and decreased f0 and speech rate when attempting to sound older. Study 2 showed that the voice manipulations had an effect in the sought-after direction, although the achieved mean effect was only 3 years, which is far less than the intended effect of 20 years. Moreover, listeners used speech rate, but not f0, as a cue to speaker age. It was concluded that age disguise by voice can be achieved by naïve speakers even though the perceived effect was smaller than intended.

Cognitive hearing science is mainly about the study of how cognitive factors contribute to speech comprehension, but cognitive factors also partake in speech processing to infer non-linguistic information from speech signals, such as the intentions of the talker and the speaker’s age. Here, we report two experiments on age estimation by “naïve” listeners. The aim was to study how speech rate influences estimation of speaker age by comparing the speakers’ natural speech rate with increased or decreased speech rate. In Experiment 1, listeners were presented with audio samples of read speech from three different speaker age groups (young, middle aged, and old adults). They estimated the speakers as younger when speech rate was faster than normal and as older when speech rate was slower than normal. This speech rate effect was slightly greater in magnitude for older (60–65 years) speakers in comparison with younger (20–25 years) speakers, suggesting that speech rate may gain greater importance as a perceptual age cue with increased speaker age. This pattern was more pronounced in Experiment 2, in which listeners estimated age from spontaneous speech. Faster speech rate was associated with lower age estimates, but only for older and middle aged (40–45 years) speakers. Taken together, speakers of all age groups were estimated as older when speech rate decreased, except for the youngest speakers in Experiment 2. The absence of a linear speech rate effect in estimates of younger speakers, for spontaneous speech, implies that listeners use different age estimation strategies or cues (possibly vocabulary) depending on the age of the speaker and the spontaneity of the speech. Potential implications for forensic investigations and other applied domains are discussed.