1. RESPITE - Meeting Saillon 25.-26.1.1

2. Introduction ‘Full Combination’ Subband Approach

3. Reminder: FC, AFC & PoE  no assumptions  assumption of conditional independence  assumption of independence

4. A Model for Context Effects w consists of n elements i=1..n having the probability q i for correct recognition probability of complete stimulus p(w) = q 1 q 2 … q n probability of incomplete stimulus p(w in ) = (1- q 1 ) q 2 …q n probability of no element correct p(w in ) = (1- q 1 ) (1-q 2 )…(1-qn) 2.use of contextual information to fill in the missing parts of an incomplete stimulus  [Bronkhorst,Bosman,Smoorenburg,1993] : 2-stage process for the recognition of a stimulus 1.use of only sensory information to identify a stimulus w

5. 1. Use of Sensory Information A stimulus can be perceived with 0 to n errors : Q 0 = q 1 q 2 … q n Q 1 = (1-q 1 )q 2 … q n + q 1 (1-q 2 ) … q n + … + q 1 … q n-1 (1-q n ). Q n = (1-q 1 )(1-q 2 )…(1-q n ) In each Q i it is summed over possible permutations of i missing elements Note: q i = probability of recognizing element i without context

6. 2. Use of Context Information Use of contextual information to fill in the missing parts of an incomplete stimulus c i : chance of correctly guessing one missing element when i elements were missed c 1 : chance of correctly guessing 1 missing element when 1 element was missed c 1 c 2 : chance of correctly guessing 2 missing element when 2 elements were missed => for guessing all missing elements correctly c 1 c 2 … c n

7. Combine 1. and 2. The probabilities of occurrence of the elements of all possible percepts: Q 0 = q 1 q 2 … q n Q 1 = (1-q 1 )q 2 … q n + q 1 (1-q 2 ) … q n + … + q 1 … q n-1 (1-q n ). Q n = (1-q 1 )(1-q 2 )…(1-q n ) are multiplied with the chance c i of guessing the missed elements. It is then summed over all possible percepts : p(w) = Q 0 +c 1 Q 1 + c 1 c 2 Q 2 +…+ c 1 …c n Q n

8. Comparison to AFC and FC

9. Implementation c i = priors P(q) Possibilities to choose c i : c i c i-1 … c 1 =

10. Experiments

13. Conclusion  AFC: no significant improvement with BBS’ context model using BBS’ context model gave a small improvement in clean (from 9 to 8.4 %) but degradation in high noise  FC:  PoE : cannot compete on its own (except for some noise cases) does not seem to harm in BBS