Vocal Affect Research Articles

The influence of affective voice on sound distance perception.

Affective stimuli in our environment indicate reward or threat and thereby relate to approach and avoidance behavior. Previous findings suggest that affective stimuli may bias visual perception, but it remains unclear whether similar biases exist in the auditory domain. Therefore, we asked whether affective auditory voices (angry vs. neutral) influence sound distance perception. Two VR experiments (data collection 2021-2022) were conducted in which auditory stimuli were presented via loudspeakers located at positions unknown to the participants. In the first experiment (N = 44), participants actively placed a visually presented virtual agent or virtual loudspeaker in an empty room at the perceived sound source location. In the second experiment (N = 32), participants were standing in front of several virtual agents or virtual loudspeakers and had to indicate the sound source by directing their gaze toward the perceived sound location. Results in both preregistered experiments consistently showed that participants estimated the location of angry voice stimuli at greater distances than the location of neutral voice stimuli. We discuss that neither emotional nor motivational biases can account for these results. Instead, distance estimates seem to rely on listeners' representations regarding the relationship between vocal affect and acoustic characteristics. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Mother-infant self- and interactive contingency at four months and infant cognition at one year: A view from microanalysis

Although a considerable literature documents associations between early mother-infant interaction and cognitive outcomes in the first years of life, few studies examine the contributions of contingently coordinated mother-infant interaction to infant cognitive development. This study examined associations between the temporal dynamics of the contingent coordination of mother-infant face-to-face interaction at 4 months and cognitive performance on the Bayley Scales of Infant Development at age one year in a sample of (N = 100) Latina mother-infant pairs. Split-screen videotaped interactions were coded on a one second time base for the communication modalities of infant and mother gaze and facial affect, infant vocal affect, and mother touch. Multi-level time-series models evaluated self- and interactive contingent processes in these modalities and revealed 4-month patterns of interaction associated with higher one-year cognitive performance, not identified in prior studies. Infant and mother self-contingency, the moment-to-moment probability that the individual’s prior behavior predicts the individual’s future behavior, was the most robust measure associated with infant cognitive performance. Self-contingency findings showed that more varying infant behavior was optimal for higher infant cognitive performance, namely, greater modulation of negative affect; more stable maternal behavior was optimal for higher infant cognitive performance, namely, greater likelihood of sustaining positive facial affect. Although interactive contingency findings were sparse, they showed that, when mothers looked away, or dampened their faces to interest or mild negative facial affect, infants with higher 12-month cognitive performance were less likely to show negative vocal affect. We suggest that infant ability to modulate negative affect, and maternal ability to sustain positive affect, may be mutually reinforcing, together creating a dyadic climate that is associated with more optimal infant cognitive development.

Gender stereotypes and social perception of vocal confidence is mitigated by salience of socio-indexical cues to gender.

Socio-indexical cues to gender and vocal affect often interact and sometimes lead listeners to make differential judgements of affective intent based on the gender of the speaker. Previous research suggests that rising intonation is a common cue that both women and men produce to communicate lack of confidence, but listeners are more sensitive to this cue when it is produced by women. Some speech perception theories assume that listeners will track conditional statistics of speech and language cues (e.g., frequency of the socio-indexical cues to gender and affect) in their listening and communication environments during speech perception. It is currently less clear if these conditional statistics will impact listener ratings when context varies (e.g., number of talkers). To test this, we presented listeners with vocal utterances from one female and one male-pitched voice (single talker condition) or many female/male-pitched voices (4 female voices; 4 female voices pitch-shifted to a male range) to examine how they impacted perceptions of talker confidence. Results indicated that when one voice was evaluated, listeners defaulted to the gender stereotype that the female voice using rising intonation (a cue to lack of confidence) was less confident than the male-pitched voice (using the same cue). However, in the multi-talker condition, this effect went away and listeners equally rated the confidence of the female and male-pitched voices. Findings support dual process theories of information processing, such that listeners may rely on heuristics when speech perception is devoid of context, but when there are no differentiating qualities across talkers (regardless of gender), listeners may be ideal adapters who focus on only the relevant cues.

Frontal mechanisms underlying primate calls recognition by humans.

The ability to process verbal language seems unique to humans and relies not only on semantics but on other forms of communication such as affective vocalizations, that we share with other primate species-particularly great apes (Hominidae). To better understand these processes at the behavioral and brain level, we asked human participants to categorize vocalizations of four primate species including human, great apes (chimpanzee and bonobo), and monkey (rhesus macaque) during MRI acquisition. Classification was above chance level for all species but bonobo vocalizations. Imaging analyses were computed using a participant-specific, trial-by-trial fitted probability categorization value in a model-based style of data analysis. Model-based analyses revealed the implication of the bilateral orbitofrontal cortex and inferior frontal gyrus pars triangularis (IFGtri) respectively correlating and anti-correlating with the fitted probability of accurate species classification. Further conjunction analyses revealed enhanced activity in a sub-area of the left IFGtri specifically for the accurate classification of chimpanzee calls compared to human voices. Our data-that are controlled for acoustic variability between species-therefore reveal distinct frontal mechanisms that shed light on how the human brain evolved to process vocal signals.

Associations of maternal postpartum depressive and anxiety symptoms with 4-month infant and mother self- and interactive contingency of gaze, affect, and touch.

Maternal depression and anxiety are associated with infant and mother self- and interactive difficulties. Although maternal depression and anxiety usually co-occur, studies taking this comorbidity into account are few. Despite some literature, we lack a detailed understanding of how maternal depressive and anxiety symptoms may be associated with patterns of mother-infant interaction. We examined associations of maternal postpartum depressive and anxiety symptoms with infant and mother self- and interactive patterns by conducting multi-level time-series models in a sample of 56 Turkish mothers and their 4-month infants. Time-series models assessed the temporal dynamics of interaction via infant and mother self- and interactive contingency. Videotaped face-to-face interaction was coded on a 1s time base for infant and mother gaze and facial affect, infant vocal affect, and mother touch. Results indicated that mothers with high depressive symptoms were vulnerable to infants looking away, reacting with negative touch; their infants remained affectively midrange, metaphorically distancing themselves from mothers' affect. Mothers with high anxiety symptoms were vulnerable to infants becoming facially dampened and mothers reacted with negative facial affect. Altered infant and mother self-contingency patterns were largely opposite for maternal depressive and anxiety symptoms. These patterns describe foundational processes by which maternal postpartum mood is transmitted to the infant and which may affect infant development.

Validation of scrambling methods for vocal affect bursts

Studies on perception and cognition require sound methods allowing us to disentangle the basic sensory processing of physical stimulus properties from the cognitive processing of stimulus meaning. Similar to the scrambling of images, the scrambling of auditory signals is aimed at creating stimulus instances that are unrecognizable but have comparable low-level features. In the present study, we generated scrambled stimuli of short vocalizations taken from the Montreal Affective Voices database (Belin et al., Behav Res Methods, 40(2):531–539, 2008) by applying four different scrambling methods (frequency-, phase-, and two time-scrambling transformations). The original stimuli and their scrambled versions were judged by 60 participants for the apparency of a human voice, gender, and valence of the expressions, or, if no human voice was detected, for the valence of the subjective response to the stimulus. The human-likeness ratings were reduced for all scrambled versions relative to the original stimuli, albeit to a lesser extent for phase-scrambled versions of neutral bursts. For phase-scrambled neutral bursts, valence ratings were equivalent to those of the original neutral burst. All other scrambled versions were rated as slightly unpleasant, indicating that they should be used with caution due to their potential aversiveness.

Affect in Infant-Directed Speech of Swedish-Speaking Mothers and Fathers to 3-, 6-, 9-, and 12-Month-Old Infants

ABSTRACT Infant-directed speech (IDS) is characterized by a range of register-typical characteristics. Many of those can be objectively measured, such as acoustic-prosodic and structural-linguistic modifications. Perceived vocal affect, however, is a socio-emotional IDS characteristic and is subjectively assessed. Vocal affect goes beyond acoustic-prosodic and structural-linguistic IDS features and includes a perceptive-subjective component in the listener. This study describes vocal affect valence in Swedish IDS during the first year of life, and compares vocal affect between mothers’ and fathers’ IDS and their adult-directed speech. Adult native speakers of Swedish (N = 16) rated affect valence in low-pass filtered IDS samples from free play interactions of mothers with infants at 3, 6, 9, and 12 months (N = 10) and fathers with their 12-month-olds (N = 6). Across the first year, the trajectory of mothers’ positive affect in Swedish IDS shows the highest affect scores toward the youngest infants and the lowest at 9 months of age. This follows a pattern comparable to that in Australian English IDS, showing that mothers express vocal affect similarly across different languages and cultures. Both mothers’ and fathers’ IDS to 12-month-olds have higher positive vocal affect valence than their adult-directed speech. There was no difference in positive affect valence between mothers’ and fathers’ IDS, that is, mothers and fathers express vocal affect to the same extent when talking to their infants. In conclusion, the findings of this study indicate that high positive vocal affect characterizes IDS across different languages and speakers.

Humans recognize affective cues in primate vocalizations: acoustic and phylogenetic perspectives

Humans are adept at extracting affective information from vocalizations of humans and other animals. However, the extent to which human recognition of vocal affective cues of other species is due to cross-taxa similarities in acoustic parameters or the phylogenetic closeness between species is currently unclear. To address this, we first analyzed acoustic variation in 96 affective vocalizations, taken from agonistic and affiliative contexts, of humans and three other primates—rhesus macaques (Macaca mulatta), chimpanzees and bonobos (Pan troglodytes and Pan paniscus). Acoustic analyses revealed that agonistic chimpanzee and bonobo vocalizations were similarly distant from agonistic human voices, but chimpanzee affiliative vocalizations were significantly closer to human affiliative vocalizations, than those of bonobos, indicating a potential derived vocal evolution in the bonobo lineage. Second, we asked 68 human participants to categorize and also discriminate vocalizations based on their presumed affective content. Results showed that participants reliably categorized human and chimpanzee vocalizations according to affective content, but not bonobo threat vocalizations nor any macaque vocalizations. Participants discriminated all species calls above chance level except for threat calls by bonobos and macaques. Our results highlight the importance of both phylogenetic and acoustic parameter level explanations in cross-species affective perception, drawing a more complex picture to the origin of vocal emotions.

Gender congruence and emotion effects in cross-modal associative learning: Insights from ERPs and pupillary responses.

Social and emotional cues from faces and voices are highly relevant and have been reliably demonstrated to attract attention involuntarily. However, there are mixed findings as to which degree associating emotional valence to faces occurs automatically. In the present study, we tested whether inherently neutral faces gain additional relevance by being conditioned with either positive, negative, or neutral vocal affect bursts. During learning, participants performed a gender-matching task on face-voice pairs without explicit emotion judgments of the voices. In the test session on a subsequent day, only the previously associated faces were presented and had to be categorized regarding gender. We analyzed event-related potentials (ERPs), pupil diameter, and response times (RTs) of N = 32 subjects. Emotion effects were found in auditory ERPs and RTs during the learning session, suggesting that task-irrelevant emotion was automatically processed. However, ERPs time-locked to the conditioned faces were mainly modulated by the task-relevant information, that is, the gender congruence of the face and voice, but not by emotion. Importantly, these ERP and RT effects of learned congruence were not limited to learning but extended to the test session, that is, after removing the auditory stimuli. These findings indicate successful associative learning in our paradigm, but it did not extend to the task-irrelevant dimension of emotional relevance. Therefore, cross-modal associations of emotional relevance may not be completely automatic, even though the emotion was processed in the voice.

ACOUSTICALLY-DRIVEN PHONEME REMOVAL THAT PRESERVES VOCAL AFFECT CUES.

In this paper, we propose a method for removing linguistic information from speech for the purpose of isolating paralinguistic indicators of affect. The immediate utility of this method lies in clinical tests of sensitivity to vocal affect that are not confounded by language, which is impaired in a variety of clinical populations. The method is based on simultaneous recordings of speech audio and electroglotto-graphic (EGG) signals. The speech audio signal is used to estimate the average vocal tract filter response and amplitude envelop. The EGG signal supplies a direct correlate of voice source activity that is mostly independent of phonetic articulation. These signals are used to create a third signal designed to capture as much paralinguistic information from the vocal production system as possible-maximizing the retention of bioacoustic cues to affect-while eliminating phonetic cues to verbal meaning. To evaluate the success of this method, we studied the perception of corresponding speech audio and transformed EGG signals in an affect rating experiment with online listeners. The results show a high degree of similarity in the perceived affect of matched signals, indicating that our method is effective.

Associations between prenatal exposure to second hand smoke and infant self-regulation in a New York city longitudinal prospective birth cohort

BackgroundPrenatal exposure to active or passive maternal smoking –also referred to as second hand smoke (SHS) exposure – are associated with externalizing behaviors, hyperactivity and attention deficit hyperactivity disorder, problems which derive in part from altered self-regulation. ObjectivesDetermine the influence of prenatal SHS on infant self-regulation using direct measures of infant behavior in 99 mothers from the Fair Start birth cohort followed at the Columbia Center for Children's Environmental Health. MethodsSelf-regulation was operationalized with self-contingency, the likelihood of maintaining/changing behavior from second-to-second, measured via split-screen video recordings of mothers playing with their 4-month infants. Mother and infant facial and vocal affect, gaze-on/-off partner, and mother touch were coded on a 1 s time-base. Third trimester prenatal SHS was assessed via self-report of a smoker in the home. Weighted-lag time-series models tested conditional effects of SHS-exposure (vs. non-exposure) on infant self-contingency for eight modality-pairings (e.g., mother gaze-infant gaze). Individual-seconds time-series models and analysis of predicted values at t0 interrogated significant weighted-lag findings. Because prior findings link developmental risk factors with lowered self-contingency, we hypothesized that prenatal SHSSHS would predict lowered infant self-contingency. ResultsRelative to non-exposed infants, those who were prenatally exposed to SHS had lower self-contingency (more variable behavior) in all eight models. Follow-up analyses showed that, given infants were likely to be in the most negative facial or vocal affect, those with prenatal SHS were more likely to make larger behavioral changes, moving into less negative or more positive affect and to alternate between gaze-on and off mother. Mothers who were exposed to SHS during pregnancy (vs. non-exposed) showed a similar, albeit less prevalent, pattern of larger changes out of negative facial affect. ConclusionThese findings extend prior work linking prenatal SHS with youth dysregulated behavior, showing similar effects in infancy, a critically important period that sthe stage for future child development.

What do you have in mind? ERP markers of visual and auditory imagery

This study aimed to investigate the psychophysiological markers of imagery processes through EEG/ERP recordings. Visual and auditory stimuli representing 10 different semantic categories were shown to 30 healthy participants. After a given interval and prompted by a light signal, participants were asked to activate a mental image corresponding to the semantic category for recording synchronized electrical potentials. Unprecedented electrophysiological markers of imagination were recorded in the absence of sensory stimulation. The following peaks were identified at specific scalp sites and latencies, during imagination of infants (centroparietal positivity, CPP, and late CPP), human faces (anterior negativity, AN), animals (anterior positivity, AP), music (P300-like), speech (N400-like), affective vocalizations (P2-like) and sensory (visual vs auditory) modality (PN300). Overall, perception and imagery conditions shared some common electro/cortical markers, but during imagery the category-dependent modulation of ERPs was long latency and more anterior, with respect to the perceptual condition. These ERP markers might be precious tools for BCI systems (pattern recognition, classification, or A.I. algorithms) applied to patients affected by consciousness disorders (e.g., in a vegetative or comatose state) or locked-in-patients (e.g., spinal or SLA patients).

Event-related brain potential markers of visual and auditory perception: A useful tool for brain computer interface systems.

A majority of BCI systems, enabling communication with patients with locked-in syndrome, are based on electroencephalogram (EEG) frequency analysis (e.g., linked to motor imagery) or P300 detection. Only recently, the use of event-related brain potentials (ERPs) has received much attention, especially for face or music recognition, but neuro-engineering research into this new approach has not been carried out yet. The aim of this study was to provide a variety of reliable ERP markers of visual and auditory perception for the development of new and more complex mind-reading systems for reconstructing the mental content from brain activity. A total of 30 participants were shown 280 color pictures (adult, infant, and animal faces; human bodies; written words; checkerboards; and objects) and 120 auditory files (speech, music, and affective vocalizations). This paradigm did not involve target selection to avoid artifactual waves linked to decision-making and response preparation (e.g., P300 and motor potentials), masking the neural signature of semantic representation. Overall, 12,000 ERP waveforms × 126 electrode channels (1 million 512,000 ERP waveforms) were processed and artifact-rejected. Clear and distinct category-dependent markers of perceptual and cognitive processing were identified through statistical analyses, some of which were novel to the literature. Results are discussed from the view of current knowledge of ERP functional properties and with respect to machine learning classification methods previously applied to similar data. The data showed a high level of accuracy (p ≤ 0.01) in the discriminating the perceptual categories eliciting the various electrical potentials by statistical analyses. Therefore, the ERP markers identified in this study could be significant tools for optimizing BCI systems [pattern recognition or artificial intelligence (AI) algorithms] applied to EEG/ERP signals.

Disentangling emotional signals in the brain: an ALE meta-analysis of vocal affect perception.

Recent advances in neuroimaging research on vocal emotion perception have revealed voice-sensitive areas specialized in processing affect. Experimental data on this subject is varied, investigating a wide range of emotions through different vocal signals and task demands. The present meta-analysis was designed to disentangle this diversity of results by summarizing neuroimaging data in the vocal emotion perception literature. Data from 44 experiments contrasting emotional and neutral voices was analyzed to assess brain areas involved in vocal affect perception in general, as well as depending on the type of voice signal (speech prosody or vocalizations), the task demands (implicit or explicit attention to emotions), and the specific emotion perceived. Results reassessed a consistent bilateral network of Emotional Voices Areas consisting of the superior temporal cortex and primary auditory regions. Specific activations and lateralization of these regions, as well as additional areas (insula, middle temporal gyrus) were further modulated by signal type and task demands. Exploring the sparser data on single emotions also suggested the recruitment of other regions (insula, inferior frontal gyrus, frontal operculum) for specific aspects of each emotion. These novel meta-analytic results suggest that while the bulk of vocal affect processing is localized in the STC, the complexity and variety of such vocal signals entails functional specificities in complex and varied cortical (and potentially subcortical) response pathways.

Characterizing difficulties with emotion regulation in toddlers with autism spectrum disorder

BackgroundDifficulties with emotion regulation (ER) underlie emotional/behavioral challenges and co-occurring psychiatric symptoms in autism spectrum disorder (ASD), yet very little is known about the early development of emotion dysregulation. The present study aimed to identify differences in positive and negative emotional reactivity and regulation strategies in toddlers with and without ASD. MethodNine tasks from the Laboratory Temperament Assessment Battery (Lab-TAB) were completed with 37 toddlers with and without ASD (22–28 months). Video-recordings of these tasks were coded by research assistants using a behavioral coding scheme tapping facial, bodily, and vocal affect and the frequency of ER strategies. Mixed model analyses were performed to examine the mean affect and total regulation strategies across each task and t-tests were conducted to assess the types of ER strategies utilized. ResultsToddlers with ASD showed significantly less positive affect and greater frustration compared to non-ASD toddlers; reactivity was comparable between the groups for fear. Both groups used ER strategies in a similar pattern across tasks, with the exception that toddlers with ASD more often engaged in distraction to regulate. Effects of age and developmental level are discussed. ConclusionsToddlers with ASD were robustly characterized by greater frustration and lower joy despite frequent and age appropriate attempts to regulate their emotions. This study provides preliminary evidence that observable indicators of emotion dysregulation are present by two years of age. Clinical implications and future research directions are discussed.

Interrogating Trot, Situating the Boom: New(tro) Nostalgia, Old Songs, and National Identity Performance

Across 2019–2020 a number of South Korean TV competition shows branded their musical identity as “trot.” This term denotes a perceived genre of popular music considered normative to South Korea’s developmentalist decades and thereafter as the music of older generations, yet the surprise success of the TV shows seemingly indicated a younger uptake heralding a “trot boom.” However, in much of their choice of repertoire, the shows transgressed pre-existing expectations of the genre. The notion of a trot boom premised on a reified genre discourse is thus overly reductionist and fails to explain adequately the performed aesthetics and socio-musical phenomenon engendered by the shows. This article problematizes the received narrative(s) of “trot,” while highlighting three alternative trans-genre elements and aesthetic trends that operate in close proximity to trot discourse: “old song” collections, kug’ak (traditional music) fusion, and a discourse of Korean vocal affect. It analyzes the repertoire and performances of three of the most noted trot-branded television series, and juxtaposes them with two further case studies: YouTube channel Chu Hyŏnmi TV and a sample of “old song” collections dating 1969–1989. It argues that all three cases variously intersect and diverge from reified trot, while simultaneously exhibiting their own interrelations collectively bound by performed retro and newtro aesthetics, and national identity discourse.

The paradoxical role of emotional intensity in the perception of vocal affect

Vocalizations including laughter, cries, moans, or screams constitute a potent source of information about the affective states of others. It is typically conjectured that the higher the intensity of the expressed emotion, the better the classification of affective information. However, attempts to map the relation between affective intensity and inferred meaning are controversial. Based on a newly developed stimulus database of carefully validated non-speech expressions ranging across the entire intensity spectrum from low to peak, we show that the intuition is false. Based on three experiments (N = 90), we demonstrate that intensity in fact has a paradoxical role. Participants were asked to rate and classify the authenticity, intensity and emotion, as well as valence and arousal of the wide range of vocalizations. Listeners are clearly able to infer expressed intensity and arousal; in contrast, and surprisingly, emotion category and valence have a perceptual sweet spot: moderate and strong emotions are clearly categorized, but peak emotions are maximally ambiguous. This finding, which converges with related observations from visual experiments, raises interesting theoretical challenges for the emotion communication literature.

Intrapersonal and interpersonal vocal affect dynamics during psychotherapy.

The present study implements an automatic method of assessing arousal in vocal data as well as dynamic system models to explore intrapersonal and interpersonal affect dynamics within psychotherapy and to determine whether these dynamics are associated with treatment outcomes. The data of 21,133 mean vocal arousal observations were extracted from 279 therapy sessions in a sample of 30 clients treated by 24 therapists. Before and after each session, clients self-reported their well-being level, using the Outcome Rating Scale. Both clients' and therapists' vocal arousal showed intrapersonal dampening. Specifically, although both therapists and clients departed from their baseline, their vocal arousal levels were "pulled" back to these baselines. In addition, both clients and therapists exhibited interpersonal dampening. Specifically, both the clients' and the therapists' levels of arousal were "pulled" toward the other party's arousal level, and clients were "pulled" by their therapists' vocal arousal toward their own baseline. These dynamics exhibited a linear change over the course of treatment: whereas interpersonal dampening decreased over time, there was an increase in intrapersonal dampening over time. In addition, higher levels of interpersonal dampening were associated with better session outcomes. These findings demonstrate the advantages of using automatic vocal measures to capture nuanced intrapersonal and interpersonal affect dynamics in psychotherapy and demonstrate how these dynamics are associated with treatment gains. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Supplemental material for Of like mind: The (mostly) similar mentalizing of robots and humans.

Mentalizing is the process of inferencing others’ mental states and contributes to an inferential system known as Theory of Mind (ToM)—a system that is critical to human interactions as it facilitates sense-making and prediction of future behaviors. As technological agents like social robots increasingly exhibit hallmarks of intellectual and social agency—and are increasingly integrated into contemporary social life—it is not yet fully understood whether humans hold ToM for such agents. To build on extant research in this domain, five canonical tests that signal implicit mentalizing (white lie detection, intention inferencing, facial affect interpretation, vocal affect interpretation, and false-belief detection) were conducted for an agent (anthropomorphic or machinic robots, or a human) through video-presented (Study 1 <#s6> ) and physically co-present interactions (Study 2 <#s20> ). Findings suggest that mentalizing tendencies for robots and humans are more alike than different, however use of non-literal language, co-present interactivity, and reliance on agent-class heuristics may reduce tendencies to mentalize robots.

Of like mind: The (mostly) similar mentalizing of robots and humans.

Mentalizing is the process of inferencing others’ mental states and contributes to an inferential system known as Theory of Mind (ToM)—a system that is critical to human interactions as it facilitates sense-making and prediction of future behaviors. As technological agents like social robots increasingly exhibit hallmarks of intellectual and social agency—and are increasingly integrated into contemporary social life—it is not yet fully understood whether humans hold ToM for such agents. To build on extant research in this domain, five canonical tests that signal implicit mentalizing (white lie detection, intention inferencing, facial affect interpretation, vocal affect interpretation, and false-belief detection) were conducted for an agent (anthropomorphic or machinic robots, or a human) through video-presented (Study 1 ) and physically co-present interactions (Study 2 ). Findings suggest that mentalizing tendencies for robots and humans are more alike than different, however use of non-literal language, co-present interactivity, and reliance on agent-class heuristics may reduce tendencies to mentalize robots.