| Theory | Description | Reflection |
| Restorative | Sleep allows for growth and repair of the body and brain. | Growth hormone secreted during non-REM sleep; protein production increases during REM; replenishment of neurotransmitters. |
| Evolutionary Consolidation | Sleep serves adaptive function; evolved as it helped survival. | Dark environments were unsafe; humans have poor night vision compared to animals hunting at night. |
| We spend appro still to be establi | Sleep aids in the consolidation of memories and learning. | Assists in creation of memories, learning difficult concepts; similar patterns of brain activity when learning and sleeping afterwards. |
| We spend approximately a third of our lives sleeping, yet the precise purpose of sleep is still to be established. Above are three of the dominant theories. |