Experimentation in point of view began around the time of 1850s in novels and have been present since.
Explanation:
The first examples of usage of unreliable POV comes from the work of detective fiction, most famously by Agatha Christie. From then on, the point of view is tried for unreliability, reality in stark time, and to show multiple perspectives.
Nowadays many novels have multiple point of views narrating chapters in the same story. This is also found in Faulkner's work.
The modern work on Point of view is based on an assumption on how human psyche works.
