Causal inference in cue combination Konrad Kording
Modeling: Where do cues come from? Generate
Traditional Bayesian model Infer Alais & Burr 04, Battaglia et al 03, Knill & Pouget 04, Ernst & Banks 02, Gahramani 95, van Beers et al, etc
Visual Auditory combination (Ventriloquist effect) Both cues
What would happen now?
Do we believe this kind of model? Assumes there is one and only one cause!
Alternative model or Kording, Beierholm, Ma, Quartz, Tenenbaum, Shams, 2007
Calculate probability of model Using Bayes rule:
Independent causes: where is the auditory stimulus Audio Visual Best estimate
Common cause: where is the auditory stimulus Audio Visual Combined Best estimate
Mean squared error estimate Audio Visual Combine Best estimate Remark: Knill uses virtually identical math
Experimental test Wallace et al 2005 Hairston et al 2004 Button: common cause or two
Measured gain Wallace et al 2005 Hairston et al 2004 Data Kording et alSato et al, in press
How can the gain be negative?
Predicting the variance Worse prediction if we assume model selection
Take home message Uncertainty about causal structure Bayesian framework is modular Easy to extend Causality problems occur in many domains
Acknowledgements Ulrik Beierholm Wei Ji Ma Steven Quartz Joshua Tenenbaum Ladan Shams Kunlin Wei