When I was 9 or 10 years old, I had a routine medical examination at school. As far as I could tell, this showed up nothing of note – certainly, the doctor gave no indication that anything was untoward – so I was surprised to hear from my mother that the doctor had reported a visual problem, specifically that he believed that I was red/green colour blind. With the certainty of youth I refused to believe this : I knew perfectly well that I could see traffic lights and the like so I was confident that I could not be colour blind. What the doctor was actually reporting was that I had not given the correct responses to a standard procedure known as the Ishihara Test which conceals numbers within patterns of coloured dots. Apparently subjects with “normal” colour vision see certain numbers and those with “defects” see other numbers or nothing at all.
To me, this made little sense since I knew that I could see a full range of colours. Moreover, I could see exceptional colours – I clearly remember seeing a warship moored on the Thames at London and recall with absolute certainty that it was not the usual dull grey but a vivid pink! Likewise I had seen a bowling green that was surfaced with bright red grass. Both of these experiences were clearly quite odd, not to say impossible by conventional wisdom. Nonetheless, to me these were absolutely real perceptions and suggested that the situation was more complex than was implied by a simplistic diagnosis.
Years passed and I continued to wonder quite what was going on. It was not until I started to read about the cognitive experience of colour (what do we mean by blue or yellow and what is the nature of our experience when we see them?) that I began to realise that the perception of colour could not be simply mechanistic as the conventional wisdom insisted. This stated unequivocally that people like me who “suffered” from “colour blindness” had a different collection of cells in their retinas such that the necessary receptors for specific colours were physically absent and hence the colours to which they would have been attuned could not be seen. I knew from experience that this was, at best, a partial explanation and at worst, hopelessly wrong. I could see the colours without difficulty but I found it hard to identify them by name. This struck me as clearly a cognitive rather than a physiological issue so recent research that suggests that what one person sees as “blue” might well be seen by someone else as “red” has proved heartening.
The only solid conclusion that can currently be drawn appears to be that the process of the perception and experience of colour is a complex, multi-stage one that is not susceptible to explanation by simple reductionist physical models. Interestingly there appears to be some evidence that people whose brains are differently wired (e.g. on the autistic spectrum) may have different perceptions and experiences of colour. Perhaps this is the tip of a massive iceberg whereby we have now to question the universality of human perceptual experience. It may be that we have to acknowledge that, as individuals, we each inhabit, maybe even create a unique world that is ours and ours alone.