Read the scenario and answer the questions that follow it. In a laboratory study of sleep deprivation, researchers employed a variety of techniques to keep volunteers awake for variable amounts of time. One group of participants was kept awake for 24 hours, and the other was kept awake for 48 hours. During periods of forced wakefulness, participants were required to engage verbal learning tasks such as memorizing the definitions of obscure English words. At the conclusion of the period of forced wakefulness, participants were allowed to sleep for as long as they wanted to. When participants awakened, researchers tested them on the learning tasks they completed during the periods of forced wakefulness. The researchers discovered that participants who were deprived of sleep for 48 hours recalled less than those who had been forced to remain awake for 24 hours. 1a. What is the independent variable