Doris J. Kistler

Early experience is associated with the development of categorical representations for facial expressions of emotion

A fundamental issue in human development concerns how the young infants ability to recognize emotional signals is acquired through both biological programming and learning factors. This issue is extremely difficult to investigate because of the variety of sensory experiences to which humans are exposed immediately after birth. We examined the effects of emotional experience on emotion recognition by studying abused children, whose experiences violated cultural standards of care. We found that the aberrant social experience of abuse was associated with a change in childrens perceptual preferences and also altered the discriminative abilities that influence how children categorize angry facial expressions. This study suggests that affective experiences can influence perceptual representations of basic emotions.

Development of Perceptual Expertise in Emotion Recognition

How do childrens early social experiences influence their perception of emotion-specific information communicated by the face? To examine this question, we tested a group of abused children who had been exposed to extremely high levels of parental anger expression and physical threat. Children were presented with arrays of stimuli that depicted the unfolding of facial expressions, from neutrality to peak emotions. The abused children accurately recognized anger early in the formation of the facial expression, when few physiological cues were available. The speed of childrens recognition was associated with the degree of anger/hostility reported by the childs parent. These data highlight the ways in which perceptual learning can shape the timing of emotion perception.

A New Approach to the Study of Human Sound Localization

Our interactions with the world around us depend heavily on information supplied by the auditory system. Information about the presence and identity of a sound source is obviously important. However, the location of the sound is often equally important. In everyday life localization seems so automatic and generally so precise that we much more often find ourselves concentrating on “what” rather than “where.” Nevertheless, localization is an important auditory function, and the details of how it is accomplished in the auditory system are not well understood.

On the discriminability of virtual and real sound sources

A method for direct comparison between virtual and real sound sources has been developed in which listeners are presented with real sources while wearing small headphones over which virtual sources may also be presented. Adequacy of this method is assessed both acoustically and psychophysically by comparing virtual free-field stimulation to actual free-field stimulation produced by loudspeakers in an anechoic chamber. The effects of windowing the impulse response of the correction filter used for virtual synthesis are also examined. Using this method, it is concluded that when no windowing is applied to the correction filter impulse response (20.48 ms in duration at a 100 kHz sampling rate), stimulation resulting from virtual synthesis is indiscriminable from real sound source stimulation. As window length is decreased, successive increases in discriminability are observed, however. These psychophysical results are consistent with acoustic validation measures.

Multidimensional scaling analysis of head-related transfer functions

Accurate rendering of auditory objects in a virtual auditory display depends on signal processing that is based on detailed measurements of the human free-field to eardrum transfer function (HRTF). The performance of an auditory display can be severely compromised if the HRTF measurements are not made individually, for each potential user. This requirement could sharply limit the practical application of auditory display technology. Thus, we have been working to develop a standard set of HRTFs that could be used to synthesize veridical virtual auditory objects for all users. Our latest effort along those lines has involved a feature analysis of HRTFs from 15 listeners who demonstrated high proficiency localizing virtual sources. The primary objectives were to quantify the differences among HRTFs, to identify listeners with similar and different HRTFs, and to test the localizability of virtual sources synthesized from the HRTFs of an individual with closely and not closely matched HRTFs. We used a multidimensional scaling algorithm, a statistical procedure which assesses the similarity of a set of objects and/or individuals, to analyze the HRTFs of the 15 listeners. Listeners with similar HRTFs were identified and their ability to localize virtual sources synthesized from the HRTFs of a similar listener was evaluated. All listeners were able to localize accurately. When these same listeners were tested with virtual sources synthesized from HRTFs that were identified to be different by the MDS analysis. Both azimuth and elevation of virtual sources were judged less accurately. Although we were able to identify typical listeners from the MDS analysis, our preliminary data suggest that several alternative sets of HRTFs may be necessary to produce a usable auditory display system.<<ETX>>

Development and evaluation of an inventory to assess adult stutterers' communication attitudes

Abstract The purpose of this study was to develop and evaluate a procedure to assess adult stutterers communication attitudes. To this end, the investigation was divided into two phases. In Phase I, an assessment inventory based on a tripartite attitudinal model was developed and administered to 107 adult stutterers. Reliability and validity of these procedures were examined, and the inventory was refined. In Phase II, reliability and validity of the attitude assessment procedures were reassessed, and the attitudes of 26 stutterers and 56 nonstutterers were examined. Assessment procedures involved a self-report inventory, which obtained ratings of items in 13 situational subscales representing different speaking situations. These situations were rated using four response scales reflecting behavioral, affective, and cognitive aspects of attitude. Situational responding, response scale scores, and response scale interrelationships are examined. Findings are discussed in terms of the potential value of the inventory and future investigations.