Sid's talk focused on how a player's psychology enters into gameplay and as designers, we often miss these important clues. This is evident in many ways such as the Winning Paradox where the player expects to win the game everytime. Sid commented that he's never received letters when a game was won by a player.
The reward and punishment mechanic is also an important place to pay attention to the player's psychological reactions. The player never questions when gifts are given in the game, but if something bad happens, they think that the game is broken or cheating. The key is to explain why a punishment happens.
Sid then spoke on what he called the "Unholy Alliance," which is the bond between the player and the designer. He cited an humorous example from Civilation Revolutions where the player complained when they lost a battle with 3 to 1 odds in their favor. They felt that with those odds they shouldn't have lost. They also didn't complain when the 3 to 1 odds where against them and they won. They accepted a lose when the odds were 2 to 1, but not when it was 20 to 10. The game needed to be changed to compensate in order to maintain a suspension of disbelief.
Sid then spoke about several game decisions that were bad decisions in a section of the presentation called, "My Bad." These included creating a real-time Civilization, the Dinos games and Civ network.