Kerstin H. Kipp

Towards Natural Gesture Synthesis: Evaluating Gesture Units in a Data-Driven Approach to Gesture Synthesis

Virtual humans still lack naturalness in their nonverbal behaviour. We present a data-driven solution that moves towards a more natural synthesis of hand and arm gestures by recreating gestural behaviour in the style of a human performer. Our algorithm exploits the concept of gesture units to make the produced gestures a continuous flow of movement. We empirically validated the use of gesture units in the generation and show that it causes the virtual human to be perceived as more natural.

Developmental Changes in Item and Source Memory: Evidence From an ERP Recognition Memory Study With Children, Adolescents, and Adults

Event-related potential (ERP) correlates of item and source memory were assessed in 18 children (7-8 years), 20 adolescents (13-14 years), and 20 adults (20-29 years) performing a continuous recognition memory task with object and nonobject stimuli. Memory performance increased with age and was particularly low for source memory in children. The ERP difference between first presentations of objects and nonobjects, reflecting generic novelty processing, showed only small developmental changes. Regarding item memory, adults showed the putative ERP correlates of familiarity and recollection, whereas ERP effects in children and adolescents suggested a strong reliance on recollection. ERP correlates of source memory refined with age, suggesting maturation of strategic recollection between childhood and adolescence and the development of postretrieval control until adulthood.

The development of selective inhibitory control: The influence of verbal labeling

The role of language in the development of selective inhibitory control was examined in four groups: Children aged 7-9 years, children aged 11-13 years, adults aged 20-27 years, and adults aged 62-76 years. We used a modified stop-signal task in which participants inhibited or executed responses based on a visual signal. Response execution and inhibition were assessed by measurement of reaction times (RTs) and error rates to a go signal and RTs to a stop signal. Four task variations were compared in which subjects named (1) the stimulus, (2) the intended action (go/stop), (3) something irrelevant, or (4) nothing. Results showed different developmental trends for response execution and inhibition across the lifespan. Moreover, response execution was faster and more accurate when subjects named the stimulus instead of the intended action. The increase in response accuracy when naming the stimulus was greatest for children. In contrast to expectations, naming the intended action did not influence response inhibition. Overall, these findings suggest that verbal labeling supports the initiation but not the inhibition of actions.

Are computer-generated emotions and moods plausible to humans?

This paper presents results of the plausibility evaluation of computer-generated emotions and moods. They are generated by ALMA (A Layered Model of Affect), a real-time computational model of affect, designed to serve as a modular extension for virtual humans. By a unique integration of psychological models of affect, it provides three major affect types: emotions, moods and personality that cover short, medium, and long term affect. The evaluation of computer-generated affect is based on textual dialog situations in which at least two characters are interacting with each other. In this setup, elicited emotions or the change of mood are defined as consequences of dialog contributions from the involved characters. The results indicate that ALMA provides authentic believable emotions and moods. They can be used for modules that control cognitive processes and physical behavior of virtual humans in order to improve their lifelikeness and their believable qualities.

The persona zero-effect: evaluating virtual character benefits on a learning task with repeated interactions

Embodied agents have the potential to become a highly natural human-computer interaction device - they are already is use as tutors, presenters and assistants. However, it remains an open question whether adding an agent to an application has a measurable impact, positive or negative, in terms of motivation and learning performance. Prior studies are very diverse with respect to design, statistical power and outcome; and repeated interactions are rarely considered. We present a controlled user study of a vocabulary trainer application that evaluates the effect on motivation and learning performance. Subjects interacted either with a no-agent and with-agent version in a between-subjects design in repeated sessions. As opposed to prior work (e.g. Persona Effect), we found neither positive nor negative effects on motivation and learning performance, i.e. a Persona Zero-Effect. This means that adding an agent does not benefit the performance but also, does not distract.

Evaluating the tangible interface and virtual characters in the interactive COHIBIT exhibit

When using virtual characters in the human-computer interface the question arises of how useful this kind of interface is: whether the human user accepts, enjoys and profits from this form of interaction. Thorough system evaluations, however, are rarely done. We propose a post-questionnaire evaluation for a virtual character system that we apply to COHIBIT, an interactive museum exhibit with virtual characters. The evaluation study investigates the subjects’ experiences with the exhibit with regard to informativeness, entertainment and virtual character perception. Our subjects rated the exhibit both entertaining and informative and gave it a good overall mark. We discuss the detailed results and identify useful factors to consider when building and evaluating virtual character applications.

Alterations in the Relationship Between Hippocampal Volume and Episodic Memory Performance in Preterm Children

This study examines the relationship between episodic memory and hippocampal volume (magnetic resonance imaging [MRI] volumetry) in preterm children with uncomplicated neonatal courses (<34 weeks of gestation, birth weight <2,000 g) and controls (7–11 years). To examine episodic memory performance and retrieval processes, neuropsychological tests and a recognition experiment were used. Although preterm children showed reduced hippocampal volumes relative to controls by 12%, episodic memory accuracy was not reduced. However, only in controls hippocampal volume correlated with some measures of episodic memory. Together, behavioral and MRI results indicate a minor functional specificity of the hippocampus regarding episodic memory functions in preterm children.

Remediation of developmental dyslexia: Tackling a basic memory deficit

Remediation studies of developmental dyslexia are extremely rare. We present a single case study of an 8-year-old German developmental dyslexic boy K.H. who is hypothesized to suffer from a severe memory problem, impeding the development of normal reading functions. The memory problem especially affects the storage and access to letter–sound associations. As a consequence, the boy was initially unable to accurately and quickly name most of the 26 letters of the alphabet. A multiple-baseline across-material design with a high-frequency errorless learning procedure was set up to improve letter–name associations. The intervention improved K.H.s letter reading and even his word reading. We discuss the role of memory deficits in reading acquisition in the context of three different theoretical models. We show how such theoretical considerations can successfully guide remediation programmes.

Timing matters: age-related changes in episodic retrieval control as revealed by event-related potentials.

The retrieval of information from episodic memory involves the engagement of pre-retrieval control processes that facilitate the recovery of task-relevant information. The development of these processes was investigated here by comparing neural correlates of retrieval orientation between 13-14-year-old adolescents and young adults. In each age group, event-related potentials (ERPs) elicited by new test pictures were contrasted across two recognition memory tasks (specific vs. general retrieval tasks), which were designed to place greater demands on the recovery of perceptual information associated with each picture in the specific than in the general task. Memory accuracy was higher in the general than in the specific task but did not differ between age groups. In adults, new item ERPs at anterior sites were more positive going in the specific than in the general task from 400 to 1,200 ms. In adolescents, the onset latency of this effect was delayed by 300 ms relative to adults, even though no age differences in response speed were obtained in either task. The magnitude of the ERP new item effect in adults correlated with response accuracy, consistent with the view that pre-retrieval processes facilitate the recovery of task-relevant information. For adolescents, this relationship was only obtained for a subset of participants with early onsetting ERP effects, supporting the claim that the influence of pre-retrieval processes depends upon their temporal onset. Together, the findings suggest age-related changes in the efficiency of using control processes to facilitate successful retrieval while highlighting the role of onset latency in mediating these changes.

Infant febrile seizures: Changes in declarative memory as revealed by event-related potentials

OBJECTIVE According to a widespread opinion the vast majority of infant febrile seizures (IFS) are harmless. However, IFS are often associated with hippocampal sclerosis, which should lead to deficient episodic memory with spared context-free semantic memories. Although IFS represent the most common convulsive disorder in children, these consequences are rarely examined. METHODS We measured the hippocampal volume of 17 IFS children (7-9 years old) and an age-matched control group on the basis of MR images. Furthermore, we examined episodic and semantic memory performance with standardized neuropsychological tests. Two processes underlying recognition memory, namely familiarity and recollection, were assessed by means of event-related potentials (ERP). RESULTS The IFS children did not show a decreased hippocampus volume. Intelligence, working memory, semantic and episodic memory were intact. However, ERP indices of recognition memory subprocesses revealed deficits in recollection-based remembering that presumably relies on the integrity of the hippocampus, whereas familiarity-based remembering seemed to be intact. CONCLUSIONS Although hippocampus volume remains unaffected, IFS seems to induce functional changes in the MTL memory network, characterized by a compensation of recollection by familiarity-based remembering. SIGNIFICANCE This study significantly adds to the debate on the consequences of IFS by differentiating the impact on memory processing.