Larger reward values alone are not enough to entice more cooperation

Two experiments using an iterated prisoner's dilemma game examined under which conditions participants' cooperation rates would either change due to monetary value changes (e.g., 3 cents to 3 dollars) or not change due to numeric value changes (e.g., 3 dollars to 300 cents). A total of 102 university students played the game against a computer that employed one of four strategies across blocks. Results showed high rates of cooperation when participants played against a tit-for-tat strategy and low rates of cooperation against a random strategy. There was no change in cooperation rates due to changes in numeric value alone and a decrease in cooperation rates when large monetary values were at stake. Cooperation rates were higher and cooperation responses slower at earlier stages of the game. I argue that people's ability to strategize plays a key role in the changing rates and speed of cooperative behaviour in the prisoner's dilemma.