Frank Eisner

Cross-cultural recognition of basic emotions through nonverbal emotional vocalizations.

Emotional signals are crucial for sharing important information, with conspecifics, for example, to warn humans of danger. Humans use a range of different cues to communicate to others how they feel, including facial, vocal, and gestural signals. We examined the recognition of nonverbal emotional vocalizations, such as screams and laughs, across two dramatically different cultural groups. Western participants were compared to individuals from remote, culturally isolated Namibian villages. Vocalizations communicating the so-called “basic emotions” (anger, disgust, fear, joy, sadness, and surprise) were bidirectionally recognized. In contrast, a set of additional emotions was only recognized within, but not across, cultural boundaries. Our findings indicate that a number of primarily negative emotions have vocalizations that can be recognized across cultures, while most positive emotions are communicated with culture-specific signals.

The specificity of perceptual learning in speech processing

We conducted four experiments to investigate the specificity of perceptual adjustments made to unusual speech sounds. Dutch listeners heard a female talker produce an ambiguous fricative [?] (between [f] and [s]) in [f]- or [s]-biased lexical contexts. Listeners with [f]-biased exposure (e.g., [witlo?]; fromwitlof, “chicory”;witlos is meaningless) subsequently categorized more sounds on an [ef]-[es] continuum as [f] than did listeners with [s]-biased exposure. This occurred when the continuum was based on the exposure talker’s speech (Experiment 1), and when the same test fricatives appeared after vowels spoken by novel female and male talkers (Experiments 1 and 2). When the continuum was made entirely from a novel talker’s speech, there was no exposure effect (Experiment 3) unless fricatives from that talker had been spliced into the exposure talker’s speech during exposure (Experiment 4). We conclude that perceptual learning about idiosyncratic speech is applied at a segmental level and is, under these exposure conditions, talker specific.

A little more conversation, a little less action--candidate roles for the motor cortex in speech perception.

The motor theory of speech perception assumes that activation of the motor system is essential in the perception of speech. However, deficits in speech perception and comprehension do not arise from damage that is restricted to the motor cortex, few functional imaging studies reveal activity in the motor cortex during speech perception, and the motor cortex is strongly activated by many different sound categories. Here, we evaluate alternative roles for the motor cortex in spoken communication and suggest a specific role in sensorimotor processing in conversation. We argue that motor cortex activation is essential in joint speech, particularly for the timing of turn taking.

Bilateral Speech Comprehension Reflects Differential Sensitivity to Spectral and Temporal Features

Speech comprehension has been shown to be a strikingly bilateral process, but the differential contributions of the subfields of left and right auditory cortices have remained elusive. The hypothesis that left auditory areas engage predominantly in decoding fast temporal perturbations of a signal whereas the right areas are relatively more driven by changes of the frequency spectrum has not been directly tested in speech or music. This brain-imaging study independently manipulated the speech signal itself along the spectral and the temporal domain using noise-band vocoding. In a parametric design with five temporal and five spectral degradation levels in word comprehension, a functional distinction of the left and right auditory association cortices emerged: increases in the temporal detail of the signal were most effective in driving brain activation of the left anterolateral superior temporal sulcus (STS), whereas the right homolog areas exhibited stronger sensitivity to the variations in spectral detail. In accordance with behavioral measures of speech comprehension acquired in parallel, change of spectral detail exhibited a stronger coupling with the STS BOLD signal. The relative pattern of lateralization (quantified using lateralization quotients) proved reliable in a jack-knifed iterative reanalysis of the group functional magnetic resonance imaging model. This study supplies direct evidence to the often implied functional distinction of the two cerebral hemispheres in speech processing. Applying direct manipulations to the speech signal rather than to low-level surrogates, the results lend plausibility to the notion of complementary roles for the left and right superior temporal sulci in comprehending the speech signal.

Perceptual cues in nonverbal vocal expressions of emotion.

Work on facial expressions of emotions (Calder, Burton, Miller, Young, & Akamatsu, [2001]) and emotionally inflected speech (Banse & Scherer, [1996]) has successfully delineated some of the physical properties that underlie emotion recognition. To identify the acoustic cues used in the perception of nonverbal emotional expressions like laugher and screams, an investigation was conducted into vocal expressions of emotion, using nonverbal vocal analogues of the “basic” emotions (anger, fear, disgust, sadness, and surprise; Ekman & Friesen, [1971]; Scott et al., [1997]), and of positive affective states (Ekman, [1992], [2003]; Sauter & Scott, [2007]). First, the emotional stimuli were categorized and rated to establish that listeners could identify and rate the sounds reliably and to provide confusion matrices. A principal components analysis of the rating data yielded two underlying dimensions, correlating with the perceived valence and arousal of the sounds. Second, acoustic properties of the amplitude, pitch, and spectral profile of the stimuli were measured. A discriminant analysis procedure established that these acoustic measures provided sufficient discrimination between expressions of emotional categories to permit accurate statistical classification. Multiple linear regressions with participants’ subjective ratings of the acoustic stimuli showed that all classes of emotional ratings could be predicted by some combination of acoustic measures and that most emotion ratings were predicted by different constellations of acoustic features. The results demonstrate that, similarly to affective signals in facial expressions and emotionally inflected speech, the perceived emotional character of affective vocalizations can be predicted on the basis of their physical features.

Positive Emotions Preferentially Engage an Auditory–Motor “Mirror” System

Social interaction relies on the ability to react to communication signals. Although cortical sensory–motor “mirror” networks are thought to play a key role in visual aspects of primate communication, evidence for a similar generic role for auditory–motor interaction in primate nonverbal communication is lacking. We demonstrate that a network of human premotor cortical regions activated during facial movement is also involved in auditory processing of affective nonverbal vocalizations. Within this auditory–motor mirror network, distinct functional subsystems respond preferentially to emotional valence and arousal properties of heard vocalizations. Positive emotional valence enhanced activation in a left posterior inferior frontal region involved in representation of prototypic actions, whereas increasing arousal enhanced activation in presupplementary motor area cortex involved in higher-order motor control. Our findings demonstrate that listening to nonverbal vocalizations can automatically engage preparation of responsive orofacial gestures, an effect that is greatest for positive-valence and high-arousal emotions. The automatic engagement of responsive orofacial gestures by emotional vocalizations suggests that auditory–motor interactions provide a fundamental mechanism for mirroring the emotional states of others during primate social behavior. Motor facilitation by positive vocal emotions suggests a basic neural mechanism for establishing cohesive bonds within primate social groups.

Perceptual learning in speech: Stability over time (L)

Perceptual representations of phonemes are flexible and adapt rapidly to accommodate idiosyncratic articulation in the speech of a particular talker. This letter addresses whether such adjustments remain stable over time and under exposure to other talkers. During exposure to a story, listeners learned to interpret an ambiguous sound as [f] or [s]. Perceptual adjustments measured after 12 h were as robust as those measured immediately after learning. Equivalent effects were found when listeners heard speech from other talkers in the 12 h interval, and when they had the opportunity to consolidate learning during sleep.

Pre-lexical abstraction of speech in the auditory cortex

Speech perception requires the decoding of complex acoustic patterns. According to most cognitive models of spoken word recognition, this complexity is dealt with before lexical access via a process of abstraction from the acoustic signal to pre-lexical categories. It is currently unclear how these categories are implemented in the auditory cortex. Recent advances in animal neurophysiology and human functional imaging have made it possible to investigate the processing of speech in terms of probabilistic cortical maps rather than simple cognitive subtraction, which will enable us to relate neurometric data more directly to behavioural studies. We suggest that integration of insights from cognitive science, neurophysiology and functional imaging is necessary for furthering our understanding of pre-lexical abstraction in the cortex.

Developmental phonagnosia: A selective deficit of vocal identity recognition

Phonagnosia, the inability to recognize familiar voices, has been studied in brain-damaged patients but no cases due to developmental problems have been reported. Here we describe the case of KH, a 60-year-old active professional woman who reports that she has always experienced severe voice recognition difficulties. Her hearing abilities are normal, and an MRI scan showed no evidence of brain damage in regions associated with voice or auditory perception. To better understand her condition and to assess models of voice and high-level auditory processing, we tested KH on behavioural tasks measuring voice recognition, recognition of vocal emotions, face recognition, speech perception, and processing of environmental sounds and music. KH was impaired on tasks requiring the recognition of famous voices and the learning and recognition of new voices. In contrast, she performed well on nearly all other tasks. Her case is the first report of developmental phonagnosia, and the results suggest that the recognition of a speakers vocal identity depends on separable mechanisms from those used to recognize other information from the voice or non-vocal auditory stimuli.

The Brain Dynamics of Rapid Perceptual Adaptation to Adverse Listening Conditions

Listeners show a remarkable ability to quickly adjust to degraded speech input. Here, we aimed to identify the neural mechanisms of such short-term perceptual adaptation. In a sparse-sampling, cardiac-gated functional magnetic resonance imaging (fMRI) acquisition, human listeners heard and repeated back 4-band-vocoded sentences (in which the temporal envelope of the acoustic signal is preserved, while spectral information is highly degraded). Clear-speech trials were included as baseline. An additional fMRI experiment on amplitude modulation rate discrimination quantified the convergence of neural mechanisms that subserve coping with challenging listening conditions for speech and non-speech. First, the degraded speech task revealed an “executive” network (comprising the anterior insula and anterior cingulate cortex), parts of which were also activated in the non-speech discrimination task. Second, trial-by-trial fluctuations in successful comprehension of degraded speech drove hemodynamic signal change in classic “language” areas (bilateral temporal cortices). Third, as listeners perceptually adapted to degraded speech, downregulation in a cortico-striato-thalamo-cortical circuit was observable. The present data highlight differential upregulation and downregulation in auditory–language and executive networks, respectively, with important subcortical contributions when successfully adapting to a challenging listening situation.