Auditory-Visual Speech Processing (AVSP) 2013

Annecy, France
August 29 - September 1, 2013

Modulating Fusion in the McGurk Effect by Binding Processes and Contextual Noise

Olha Nahorna, Ganesh Attigodu Chandrashekara, Frédéric Berthommier, Jean Luc Schwartz

GIPSA-Lab–DPC, UMR 5216, CNRS, University of Grenoble, France

In a series of experiments we showed that the McGurk effect may be modulated by context: applying incoherent auditory and visual material before an audiovisual target made of an audio “ba” and a video “ga” significantly decreases the McGurk effect. We interpreted this as showing the existence of an audiovisual “binding” stage controlling the fusion process. Incoherence would produce “unbinding” and result in decreasing the weight of the visual input in the fusion process. In this study, we further explore this binding stage around two experiments. Firstly we test the “rebinding” process, by presenting a short period of either coherent material or silence after the incoherent ”unbinding” context. We show that coherence provides “rebinding”, resulting in a recovery of the McGurk effect. In contrary, silence provides no rebinding and hence “freezes” the unbinding process, resulting in no recovery of the McGurk effect. Capitalizing on this result, in a second experiment including an incoherent unbinding context followed by a coherent rebinding context before the target, we add noise all over the contextual period, though not in the McGurk target. It appears that noise uniformly increases the rate of McGurk responses compared to the silent condition. This suggests that contextual noise increases the weight of the visual input in fusion, even if there is no noise within the target stimulus where fusion is applied. We conclude on the role of audiovisual coherence and noise in the binding process, in the framework of audiovisual speech scene analysis and the cocktail party effect.

Index Terms: audiovisual speech perception, McGurk effect, unbinding, rebinding, perception in noise

Full Paper

Bibliographic reference.  Nahorna, Olha / Chandrashekara, Ganesh Attigodu / Berthommier, Frédéric / Schwartz, Jean Luc (2013): "Modulating fusion in the McGurk effect by binding processes and contextual noise", In AVSP-2013, 181-186.