The Relationship of Uncertainty and Complexity with Observed Bias and Interindividual Differences When Timing Audiovisual Signals

Abstract

Although in the last few decades there was an enormous progress in understanding the timing of auditory and visual signals, there are still three puzzling things yet to be unexplained: 1) often inconclusive results, 2) results depending on the task employed (such as synchrony judgment, SJ, or temporal order judgment, TOJ, tasks), and 3) high interindividual differences. Examples for the first point are studies investigating if the brain is capable of actively compensating for the different propagation speed of sound and light. Some studies finding support for such a mechanism and others do not. Given that our brain is, in opposite to a typical lab-situation, continuously bombarded with different audiovisual signals at a time it follows that the brain needs also to “decide” which auditory and visual neural activation belongs to the external event in question. Therefore, we will argue that an active compensation mechanism is insufficient and that, above all, the brain deals with an inverse problem when having to link neural signals in the presence of plenty of other competing ones. This inverse problem implies for the brain uncertainty about which of the neural signals belong together. In such a situation, and in combination with being “forced” for an action/conscious percept, information processing in the brain will lead to basically two general output alternatives: First, the output is based solely on present sensory data. In case incoming data are with regard to a decision ambiguous the output of the system (e.g., responses) will be random across trials. In this case no bias will be evident. Second, present sensory data are integrated with other data available in the system (e.g., gathered through past experience). In this case a specific bias will be evident. Such a mechanism might reduce decision time in ambiguous or complex situations.A brief overview about recent behavioral and electrophysiological findings in our lab (using SJs and TOJs) will be presented compatible with the view outlined above. I will emphasize how such a view might especially contribute to a better understanding of interindividual differences and individual bias by demonstrating: 1) influence of prior information, 2) a systematic relationship of prior information and the degree of uncertainty about present sensory data, 3) a systematic relation of task complexity (degree of freedom of possible cue or neural networks combinations) and interindividual differences.