Flies often fly in the middle of a room because they are responding to simple sensory stimuli with basic neurological mechanisms. Their flight paths may seem aimless or erratic because their nervous systems operate on simple threshold responses to stimuli like light, heat, wind, noise, movement, and the presence of food or mates. They may also be trying to maintain a fixed orientation to a light source, which can cause them to circle nearby light bulbs in enclosed spaces. Essentially, their flight in the middle of the room reflects basic survival behaviors programmed by sensory input rather than complex thought or purposeful navigation.
Additionally, flies may congregate in the center of rooms as a communal or mating behavior, choosing this spot as a common meeting place. Their movements can look like circles or rectangles due to their flight patterns.
