To study the effects of physical discomfort on attention, Dr. Lopez conducted the following study: A group of participants were required to keep one hand submerged in cold water (52 degrees). Half of the participants kept their hand in the water for 2 minutes, and half of the participants kept their hand in the water for 4 minutes. In addition, half of the participants were given a placebo pill and told it would reduce the pain of the water (pain relief assumed). The other half were given a placebo pill and told that it would have no effect (no pain relief assumed). While their hands were in the water, participants engaged in a number of tasks that required attention, with the mean time in seconds of the tasks being recorded (quicker completion meant more attention). 1. What are the independent variables in this design