How has Cassio changed from Act 1 to Act 5

I think Cassio was a bit naive in act 1 or perhaps he couldn't comprehend just how twisted Iago was. He also seemed to have faith in Othello's judgment. By act five Cassio most certainly would have looked at the world differently. The fallibility of Othello and the pure evil of his former friend Iago would have made him more skeptical of the world.