Learning to draw by understanding human vision processing

I'm feeling in an artsey mood pending the release of my ART BOOK <- Yes that is a shameless plug. So I got thinking about what our brain actually does when we try to draw things.Specifically, why is drawing lifelife objects difficult, especially from memory?I like to draw, and I often come across people who say "I wish I had that talent/skill". I personally don't believe it is an instrinsic talent, I think that anyone can learn to draw with the appropriate tuition. For the most part it involves following a fairly simple set of rules. Deciding what to draw is the 'creative' part :) When I was originally interested in drawing, I was told by teachers to always 'draw what you see'. This is an interesting statement, as what we see and how we interpret the information are two very different things.Try to draw a face without looking at a reference. You'll get it wrong. I suspect there are only a handful of people that can draw realistic faces without a reference (or without some rule of thumb/mathematically based guidelines). I personally tried to perfect this skill for years, before I actually realised that it was damn near impossible. And it wasn't a lack of general artistic 'skill' - I could draw almost perfectly from a reference.The problems associated with drawing from memory are to do with our hard-wired vision processing architecture. Our brain interprets data by using heavy compression algorithms. Lines are built up into shapes, shapes into blocks of shapes commonly found together, and these blocks of shapes along with colour information form concepts. Each level of complexity is recognised at a different level in the cortical hieracy, and each level is a compressed version of concepts from the previous one. In other words, our brain works by vector image processing.So when we hold an 'idea' of a picture in our mind, it actually looks nothing like the real-world version. It is very interesting to watch children try to draw - they construct everything out of lines and basic shapes, because this is how the concepts of those objects are stored in the brain.So how can we break this instinctive behaviour in a bid to become more artistically fluent?I think that it requires turning off your instinctive mind's-eye view of an object. There are several 'tips' that one can follow to attempt to bypass the brain's heavy image processing. Most of these are things that each artist personally rediscovers by trial and error over many years.1.) Draw based on tonality, not shape.If you see an area of shadow, shade in this region. Try to view the subject as blocks of colour, light and dark areas, not as a predefined 'object' such as a bowl of fruit or a face.2.) Never draw lines!Lines hardly ever exist in real life. They are created by your brain as a way of compressing information about a step change in brightness, saturation or colour between two areas. If you simply must draw lines, draw them faintly and then come back to it later and match the tone of the line with a filled (crosshatched/shaded, whatever) area on one side.3.) Turn the reference image upside down.This technique works amazingly well. Your immediately kill some of the recognition pathways of the brain just by inverting the object. Your brain doesn't store patterns (concepts) like 'an upside down horse' because we don't often see upside down horses.4.) Use a 'window' referencing techniqueCut a window out of a piece of paper and draw from the reference only what you see through the window (works best with a printed reference image)5.) Flip the imageIf you are working digitally, flip (mirror about x co-ordinate) both your image and the reference image quite often. You often spot mistakes immediately, and this prevents you from becoming 'accustomed' to any major errors in perspective/anatomy etc in your piece. You can do the same thing non-digitally as a check if the image is on a single side of paper - by holding it up to the light or using a lightbox. (You can't edit the other side though, this is a read-only technique!). Interestingly this method works in somewhat of an opposite way to 3.) because the flipped image is (usually) still consistent with reality, therefore you actually use your brain's ability to pattern match to spot the inconsistencies very quickly, as opposed to reducing the pattern matching it is able to perform by making the image non-realistic.6.) Observe the image from a greater distanceThis allows you to spot certain compositional errors without your brain automatically finding the focal point of the image and 'ignoring' the rest, as it does if you are close enough to see the detail.I guess the GOLDEN rule is to always use references where possible. I had an issue with this for many years as it seemed like 'cheating'. It's not cheating, it's just that our internal references don't look anything like reality, so if you want to draw something realistically, don't rely on your brain! (In fact save it for the creative part).Out of interest my book is now available on Amazon. N.B: This first publication run is IN SPANISH. For translations of the writings accompanying the artwork, you'll have to visit my website until I get the English version released. The prices and availability also seems to have screwed up a bit. I think these are just teething troubles. I'll probably put a dedicated post about it when everything has actually been sorted out properly :D