Biomedical subjects

Christian Scheier

Publications and source records attributed to Christian Scheier.

3 recordsLinked to original sources

PubMed2006

Development of multisensory spatial integration and perception in humans.

Previous studies have shown that adults respond faster and more reliably to bimodal compared to unimodal localization cues. The current study investigated for the first time the development of audiovisual (A-V) integration in spatial localization behavior in infants between 1 and 10 months of age. We observed infants' head and eye movements in response to auditory, visual, or both kinds of stimuli presented either 25 degrees or 45 degrees to the right or left of midline. Infants under 8 months of age intermittently showed response latencies significantly faster toward audiovisual targets than toward either auditory or visual targets alone They did so, however, without exhibiting a reliable violation of the Race Model, suggesting that probability summation alone could explain the faster bimodal response. In contrast, infants between 8 and 10 months of age exhibited bimodal response latencies significantly faster than unimodal latencies for both eccentricity conditions and their latencies violated the Race Model at 25 degrees eccentricity. In addition to this main finding, we found age-dependent eccentricity and modality effects on response latencies. Together, these findings suggest that audiovisual integration emerges late in the first year of life and are consistent with neurophysiological findings from multisensory sites in the superior colliculus of infant monkeys showing that multisensory enhancement of responsiveness is not present at birth but emerges later in life.

Acoustic Stimulation↗

PubMed2003

Gaze bias both reflects and influences preference.

Emotions operate along the dimension of approach and aversion, and it is reasonable to assume that orienting behavior is intrinsically linked to emotionally involved processes such as preference decisions. Here we describe a gaze 'cascade effect' that was present when human observers were shown pairs of human faces and instructed to decide which face was more attractive. Their gaze was initially distributed evenly between the two stimuli, but then gradually shifted toward the face that they eventually chose. Gaze bias was significantly weaker in a face shape discrimination task. In a second series of experiments, manipulation of gaze duration, but not exposure duration alone, biased observers' preference decisions. We thus conclude that gaze is actively involved in preference formation. The gaze cascade effect was also present when participants compared abstract, unfamiliar shapes for attractiveness, suggesting that orienting and preference for objects in general are intrinsically linked in a positive feedback loop leading to the conscious choice.

Choice Behavior↗

PubMed1998

Embedded neural networks: exploiting constraints.

Using concepts and tools of embodied cognitive science, we investigate the implications of embedding neural networks in a physical structure, the body of a robot. Embedding a neural network in a body provides constraints that can be exploited for learning. We show that the constraints are given by the environment and object properties, the agent's morphology, the agent's motor system and specific ways of interacting with the objects. We argue that designing embedded neural networks implies (a) understanding these constraints, and (b) exploiting them, i.e., designing neural networks such that they-one way or other-incorporate the constraints. This in turn results in cheap and simple networks that are suited for the task environment, and have real-time responses. Moreover, this constraint-based approach provides new perspectives on two fundamental problems of cognitive science: focus-of-attention and object constancy. The main arguments are illustrated with a series of case studies with simulated and physical mobile robots that are controlled by hand-designed as well as evolved neural networks.

Journal Article↗