When our theme now is “perception” I believe its pertinent to point to that our understanding of the role of perception lately has changed somewhat within our current understanding of how the brain functions at large.
For more than hundred years our main concept of the brain has been like a reactive information processor: We receive some sensory stimulus, which our brain then subsequently processes, and from this the brain command new acts.
For about the last decade, however, a new picture is emerging and beginning to take foothold in psychological research: That of “the predictive brain”. Related to this there is now also much more focus on the fact that for all the nerve connections that goes from our sensory neurons to the brain, there is about the same number of connections going back from the brain to our sensors. This latter fact has largely been ignored for most of the era of psychological research.
What does this mean?
Proponents of “the predictive brain” argue that the brain’s overall role is to aid our body in performing a next act in a way that likely should increase our survival. To achieve this, it’s too slow just to react on incoming sensory signals. Rather the brain constantly constructs images / spatial models of our whereabouts (also in abstract ways like our social relations), and from that it predicts what is likely the best next step. Our perception then serves to validate our predictions, and if it doesn’t, a revision of the brain model is induced. (It’s also argued that this mode of brain function is a more cost effective way for the brain to work, which of course is an evolutionary important aspect. Less eating necessary - our brain currently consumes about 20 % of our food intake.)
It also probably mean that our perception of our sensory stimuli are likely to be modified by our understanding of our surroundings and by our mental states more than we previously believed. It has e.g. been demonstrated that even such a fundamental “mechanical” function as regulating the aperture of the eye’s iris, is not determined alone by the intensity of the light reaching the eye, but that the size of the opening is influenced by what we believe is the intensity of the light.
Much of our visual response testing – and much of psychological laboratory research in general – is made within constructed research test environments where we expose participants to one or a few stimulus and focus on this in isolation. But this raises serious questions of the ecological validity of any knowledge we think gained from such tests. Because our brains and our senses normally work within a much richer environment where input from one sense is combined with others, with our previous experiences, our understanding of current context, our moods/emotions etc, all mixed together. In such a setting e.g. our perception of light strength is influenced e.g. by our perception/believes about distance to the light source – and our perception of distance is dependent on several physical aspects, not the least by moving head/body within those surroundings, and on and on an on … it’s all connected. Furthermore, attention is in general an important factor that influence our judgement of the magnitude of sensory input.
Take a look at CIE’s definition of “color, perceptual”|“perceived color”: “characteristic of visual perception that can be described by attributes of hue, brightness (or lightness) and colourfulness (or saturation or chroma)”,
and then at Note 1: “Perceived colour depends on the spectral distribution of the colour stimulus, on the size, shape, structure and surround of the stimulus area, on the state of adaptation of the observer’s visual system, and on the observer’s experience of the prevailing and similar situations of observation.”
We now know that all the three color dimensions, hue, saturation, and brightness, of color stimuli, as well as their interactions, have various effects on the emotional state of the observer. Since we know emotional state have effects on many perceptual and other cognitive aspects of our nervous system, we should likely include “mental state” into that Note 1. But as Freud once noted, (at the time he still was trying to establish a scientific psychology before he gave up due to the then lack of instruments): “Es ist nicht bequem, Gefühle wissenschaftlich zu bearbeiten.” - and for many reasons it isn’t much easier today to make research were the effect of an extensive set of emotions should be taken into account, (including because after more than 150 years of scientific psychological research there is still no agreement what an emotion is or what types of emotions there are … ).
We never perceive a pixel alone, but as part of the total image with all its variation in lightness and color, surrounded by its environment, including ambient light, and as part of our total mental state.
I see the need for getting as good an understanding of our perceptual responses as possible, and the need to create image processors with e.g. orthogonal controls with well-behaved response curves that can lead to us having tools being as accurate as possible for e.g. reproducing other images, (but we need to take into account that the perceived colors of a painting is also the result of the physical aspects of paint and light from various angles falling on it …), or doing product or portrait photography and the like.
For the rest of us who try to “create nice pictures”, we might find some relief in the fact that in seeing an image our eyes just make a few point readings and fill inn the rest as fits, something painters (and magicians) have known to “trick” us - we are deceived in the feeling of really seeing a wide picture – and from the fact that I’ve never heard any member of a photo jury declare that if it wasn’t for some deviating nuance in hue or chroma, a picture would have won an award.
TIP: In this latter respect I will make a proposition to spend some more time on the orientation module, rather than on the intricacies of the color balance module.
Why? Because most images will likely be perceived to be “better” if it complies with basic composition aspects relating to forms and lines and their contrasts and balances, (see any photo book on composition for details). However, part of our perception process is to find meaning in what we see, and in particular if there are faces or other elements of humans and their activities, this is likely catching our attention. By turning images upside down, there is in most images little immediate meaning left that can catch the attention, and hence we are better positioned to see and judge the image at its basic level of forms lines, etc.
