Articles

GameFlow: a model for evaluating player enjoyment in games
A paper on Computers in Entertainment (CIE) thoroughly developed a evaluation model based on the 8 elements of enjoyment from Mihaly Csikszentmihalyi's flow theory. It also has a nice analysis between Warcraft 3 and Lords of the Everquest based on flow experience.Download PDF.

An Experimental Test Bed to Enable Auto-dynamic Difficulty in Modern Video Games
This paper presents an experimental test bed to enable auto-dynamic difficulty adjustment in games. It supports letting the system collect data, analyze and adjust the player and NPC's attributes.

Dynamic Difficulty Adjustment
An inspiring article about whether or not should game designer to adjust the flow for the players. And also the limitation of dynamic difficulty control outside of single player game.

Learning by Design: Games as Learning Machines
Well done article about learning systems in good games. It supported the flow theory from all different aspects and also pointed that to change player's attitude from passive consumer to active agents is the key for a fluent learning experience.

The Psychology Behind Games
One very decent article talking about game design with psychology concerns.

Balancing Games with Positive Feedback
Using positive feedback to enhance and reward player's action, the amount of the feedback needs to be well cooked.

Examining Video Game Immersion as a Flow State 
A paper determining the exact nature of (positive) experience while playing a video game, coupled with video game motivation and what kinds of experiences are more gratifying/edifying to gameplay behaviour.

Researches

Mihaly Csikszentmihalyi
Professor and former chairman of the Department of Psychology at the University of Chicago who has devoted his life's work to the study of what makes people truly happy, satisfied and fulfilled, the creator of Flow theory.

• Flow: The Psychology of Optimal Experience

Bernie Dekoven
One of the creator for new games movement, who spent his entire career in researching fun and game design. He has great experience in studying fun and social gameplay.

• Flow & Coliberation

Robin Hunicke
Artificial Intelligence Phd. at northwestern university whose thesis is very close to what I'm doing. She is creating a FPS system that continually examines player progress, modifying the difficulty and pacing of in-game challenges to adjust the player's overall experience of "flow".

• AI for Dynamic Difficulty Adjustment in Games

Information Processing Technology Office
Researches to create interface that helps people to manage mass information based on cognitive feedback