Not all ghostly phenomena is attributed to the actions of intelligent spirits. Some researchers believe that certain hauntings are simply events being replayed throughout history. Known as residual hauntings, these are often events connected to strong emotions or repeated actions, and occur in the locations where the emotions were felt or actions occurred. Residual hauntings are not always visual, and can include or be solely composed of auditory and olfactory sensory experiences--witnesses report hearing footsteps repeatedly going up and down stairs or the smell of a previous resident's perfume, for instance. The locations can vary widely, from battlefields to family homes; anywhere strong emotional states are achieved or repetitive actions take place. The emotions or repeated actions are said to transfer energy into the location and create a sort of psychic imprint of their associated events, causing them to be recorded and periodically replayed.