Progress Report Reihaneh Rabbany Presented for NLP Group Computing Science Department University of Alberta April 2009

Agenda Project Proposal for Guiding Agent by Speech Many to Many Alignment by Bayesian Networks – Letter to Phoneme Alignment – Evaluation of phylogenetic trees 2

Quick RL overview An agent interacting with environment – perceives state – performs actions – receive rewards Agent – Computes the value of each action in each state long term reward obtainable from this state by performing this action – Performs action selection by choosing the best action or sometimes a random action exploration-exploitation 3

Project Proposal for Guiding Agent by Speech Accelerate learning using speech – The emotion in speech signal has considerable amount of side information – Happiness or anger of a speech signal can provide a shaping reinforcement signal Developing tools and methods to extract emotion from speech and designing a methodology to use it as a shaping signal 4

Approaches to use speech signal as a guide for learning Extracting prosodic features from speech Associating meaning to these features – Supervised learning-based approach data-set of (prosodic features, emotion) pairs – excited, happy, upset, sad, bored Assigns a reward to the recognized emotion – Pure RL approach inspired by the learning process of the parent-infant – The infant gradually learns to associate value to perceived speech and how to use it to guide her exploration of the world 5

RL Approach Two ways for developing this idea – Augmenting the observation space to include the prosodic features Emotion will become state-dependent – Learns a separate instructor module Estimates the value of prosodic features Instructions (learnt instructor values) would affect the agent's action selection 6

Instructions Different ways that these instructions (learnt instructor values) could affect the agent's action selection – Balancing the exploration-exploitation When the speaker is not happy with what the agent is doing and it should explore other actions – Use it directly in action selection by some weights Motivates the agent to keep its previous action if the instructor is satisfied with its current action – Use it as a shaping reward to define a new reward function by adding it to the actual reward received from the environment 7

Agenda Project Proposal for Guiding Agent by Speech Many to Many Alignment by Bayesian Networks – Letter to Phoneme Alignment – Evaluation of phylogenetic trees 8

Many to Many Alignment by Bayesian Networks Finding Alignment between two sequences – Assuming the order is preserved I’ve applied it into two applications – Letter to phoneme alignment Aligning for a given dictionary – Evaluating Phylogenetic trees Shows how compatible the tree is with the given taxonomy 9

Agenda Project Proposal for Guiding Agent by Speech Many to Many Alignment by Bayesian Networks – Letter to Phoneme Alignment – Phylogenetic trees evaluation 10

Model Word: – sequence of letters Pronunciation: – sequence of phonemes Alignment: – sequence of subalignments Problem: Finding the most probable alignment Assumption: sub alignments are independent 11

Many-to-Many EM 1. Initialize prob(SubAlignmnets) // Expectation Step 2. For each word in training_set 2.1. Produce all possible alignments 2.2. Choose the most probable alignment // Maximization Step 3. For all subalignments 3.1. Compute new_p(SubAlignmnets) 12

Dynamic Bayesian Network Model Subaligments : hidden variables Learn DBN by EM lili PiPi aiai 13

Context Dependent DBN Context independency assumption – Makes the model simpler – It is not always a correct assumption – Example: P( ) in Chat and Hat Model lili PiPi aiai a i-1 14

Agenda Project Proposal for Guiding Agent by Speech Many to Many Alignment by Bayesian Networks – Letter to Phoneme Alignment – Evaluation of phylogenetic trees 15

Evaluation of Phylogenetic Trees Phylogenetic Trees – Show the evolution of species Taxonomy – Caninae; True dogs; Canis; Coyote – … – Caninae; True foxes; Vulpes; Kit Fox – Caninae; True foxes; Vulpes; Fennec Fox – … – Caninae; Basal Caninae; Otocyon ; Bat-eared Fox –... 16

Tree Evaluation Labeling the inner nodes in the tree For each species – A path in the tree  sequence of inner node labels – A taxonomy description  taxonomy sequence – There should be a many to many alignment between these two sequences 17

Tree Evaluation (Cont.) Finding alignment between these sequences for all the species – Finding the most probable alignments Measuring the mean probability of these alignment – How probable is this tree given this taxonomy 18

Taxonomy and Trees Aligned result 19

Discussion 20