The five pictures are by Victorian artist Louis Wain who painted cats through the whole of his life and continued through periods of intense psychosis.
Almost every article on Wain uses them to demonstrate the progression of schizophrenia but the evidence for them being painted in chronological order is actually quite weak.
The five pictures are from an original series of eight which were collected by Dr Walter Maclay who was interested in the effect of mental illness on art.
However, the pictures were undated and, as Rodney Dale notes in his biography of Wain (Louis Wain: The Man Who Painted Cats; ISBN 1854790986), “with no evidence of the order of their progression, Maclay arranged them in a sequence which clearly demonstrated, he thought, the progressive deterioration of the artist’s mental abilities.”
In fact, his later works are for the most part conventional cat pictures in his normal style, with the occasional ‘psychedelic’ example produced at the same time – where he experimented with what he called ‘wallpaper patterns’.
However, the increasing abstraction over time is likely to be a myth. Wain’s biography again:
Assembling what little factual knowledge we have on Dr Maclay’s paintings, there is clear no justification for regarding them as more than samples of Louis Wain’s art at different times. Wain experimented with patterns and cats, and even quite late in life was still producing conventional cat pictures, perhaps 10 years after his [supposedly] ‘later’ productions which are patterns rather than cats. All of which is to say no more than that the eight paintings were done at different times, which could be said of eight paintings by any artist!