It's All in Your Mind
Visual Psychology and
Perception in Game Design
Seeing is Believing
The first and most obvious area of perception is vision, so this article concentrates on this particular type of sensory input. If I had been writing fifteen years ago, this section would only be about two paragraphs long, as the limitations on game visuals would have left me with little to say. As it is, today's games are so visually complex that what we see on the screen is beginning to rival the intricacies of the real world. Yes, it is true that a game world has significant technical limitations as to the content of a scene, but when we consider that the range of things that a game can present us with visually extends way beyond that which we will ever see in the real world, the balance begins to be redressed slightly.
Consider for a moment, the following images:
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FIGURE 3. Image A: Salvador Dali's The Slave Market With Disappearing Bust of Voltaire (1940), presents the viewer with an ambiguous image of choir boys in an archway that can also be seen as the face of the famous French Writer-Philosopher. Image B: the well known (Muller-Lyer) optical illusion, shows a row of symbols who's central vertical lines are all of equal length, despite their immediate appearance.. |
While these kind of illusions may not in themselves be of any practical use in game design, they illustrate the process by which our brain translates what it sees (stimulation of retinal cells) into what it believes this information represents, and what this means. Clearly as these images show, what we think we see, is in fact not necessarily what is actually there. Fortunately for those of us making games, our brain can be tricked into thinking it sees a whole range of things that are, in reality, no more than a collection of glowing dots of colour on a flat screen.
There are quite a selection of rules that influence how we interpret what we see. Some, like binocular disparity (the fact that our eyes are slightly separated and so receive slightly different images), have no value in the average game world (put those 3D glasses down). But certain others are of more interest.
Similarity: objects that appear the same or similar are grouped together in our mind. This can often be reinforced in a game when animation cycles of several similar objects run in synch: trees wave in the wind in unison, torches all burn at precisely the same rate. Sometimes grouping may be what we want, but more often than not, this similarity just serves to highlight the fact that some elements of a game are repeated.
Relative brightness: as things get further away from us, they tend to fade and take on a bluish hue. This phenomenon is used as a depth cue, and is of course great news for fans of fogging. The trick though, is in the subtlety and distance of the fade-out. If the fogging distance is too close, and the drop-off too severe, instead of an acceptably natural haze that reinforces the expansiveness of a landscape, the player will begin to feel that they have wandered onto the set of a 1930's Sherlock Holmes movie.
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FIGURE 4. Relative brightness: as things get further away from us, they tend to fade and take on a bluish hue. |
Scale: perhaps the most important aspect of scale is that it is relative. Perceptual consistencies, as psychology calls them, dictate that elephants are large and gerbils are small. No matter what the viewing conditions, our past experience provides us with this sort of information, which is used by our brain to decide that the elephant on a distant hill is smaller than the gerbil in our hand (Helmholtz, 1909). In a video game of course, elephants can be two feet tall and gerbils can weigh four hundred pounds. The rules of consistency are of little consequence. In addition, everything we see is effectively in screen-space, and will actually be observed in a physical sense, as being only inches high. In view of this, context within the game environment, has a large part to play.
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FIGURE 5. The effect of context on perceived brightness. |
In the example above, the central grey squares within each of the four larger squares are exactly the same. The change of brightness across the four surrounding squares however, tricks us into seeing a corresponding (but inverted) shift in brightness across the inner squares. The effect of context dependency is also valid within a game setting, when dealing with scale.
Size, relative to the player's character (or vehicle, etc.) can be used as a starting point for scale comparisons. What appears to be a human-sized character will be interpreted as such, if the surroundings reinforce this with appropriately sized trees, cars etc. If however, the character has to climb a can of beans 10 times his size, or run across a massive piano keyboard in a Tom and Jerry kind of style, the character may take up an identical amount of screen space, but will be judged to be tiny. In the same way that geometry sizing can convey scale information, textures can also have a part to play, with the scale at which a texture is applied to a surface, having a contributing (if sometimes subconscious) effect on a players sense of scale.
Speed: moving things rapidly around the screen may seem like the obvious solution in this case, but speed isn't just about being quick (not when it's on a screen at least). Let's pause for a second, and consider what most of us see as Lee Major's career high: the Bionic Man. Apart from an impressive line in polyester sportswear, one of the bionic man's most important assets was his speed. TV budgets being what they were in the Seventies, as well as the limited range of special effects on offer, the bionic man's production team had to come up with an acceptable way of making him fast. So what did they do? They slowed him down. On the one hand, this perhaps explains how the logic of this decade brought extreme chest hair into fashion and made Elton John famous, but it also makes sense. TV and film had already established the concept of slow motion, and it was of course predominantly used to show something happening too fast to be appreciated. Drawing on this convention, the bionic man gave us something that was visually slow, but translated by our brain into extreme speed. So what does this imply for creating the impression of speed in a game?
Essentially, we can use things that we associate with speed (like slow motion) as indicators that something is fast. Motion blur is perhaps the most widely used of these. Once only available as a pre-rendered effect, we now see it executed in real time. Apart from the fact that motion blur actually produces a moving image that the brain accepts as more convincing, we have now become familiar with the convention that blurring equals speed (in this respect I am talking about exaggerated, visible blurring). Roadrunner cartoons are particularly fine examples of this, building on the traditional static cartoon methodology for conveying speed. A more recent example in film would be The Matrix, where extreme, bullet-dodging speed is expressed with an adapted form of motion blur. Other visual cues to speed would include things like clouds of dust and debris in an object's wake, or the intensity of flame from a spaceship's rockets increasing (the afterburner effect). Indicators like these will help steer the player's brain towards association with speed, making the effect both easier to achieve and more convincing.
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FIGURE 6. Roadrunner cartoons are particularly fine example of how blurring is used to suggest speed. |
Once we are able to perceive the game visually, and identify its constituent elements, the next trick is making sense of it all. At this stage, there is a whole world of pain, ready to be explored when looking for a model that explains how we do this (see: Hochberg 1978, Koffka 1935 and Marr 1982), but perhaps of more interest to game design, is how we can help the process along.
Linearity in a modern game seems to have become as unpopular as a mime artist in a .....well, as unpopular as a mime artist. The days of simply routed games, where all you needed to think about was collecting giant golden keys and making your way towards a fight with the big red dragon are long gone. Free roaming, unrestricted exploration is the norm nowadays, with complex environments that allow the player to wander for hours, marvel at the scenery, and cavort across hilltops with a Julie Andrews-like abandon. But freedom comes at a price.
Dropping a player into a strange new environment can be confusing. The amount of information presented can mean that a player becomes unsure about which direction to take and unless some kind of help is available. The appeal of free exploration can be crushed under the tedium of random wandering. Solving this problem relies on good design and well-executed construction, but there is one additional area that plays a part: memory.
At the Copa… Copacabana…
Remembering where we've been, what we're doing and where we are going can (for some of us) be a difficult feat in our everyday lives. I for one often find myself staring blankly into the fridge, having no recollection of even entering the kitchen, let alone what I am looking for. Add a story line, several characters, a world full of caves and a sacred quest of some description, and suddenly, keeping track of what's going on becomes quite an issue. There are a couple of memory related problems that often crop up in games, which can in my opinion, reduce a player's enjoyment considerably:
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FIGURE 7. Remembering where we've been, what we're doing and where we are going, can, for some of us, be a difficult feat in our everyday lives. |
First, there's the common fault of information-induced panic (or IIP). We've all played games that from the very instant they start, begin to heap upon the player what seems to be vital information. Whether it's in the great hall of Castle Colon, or in the transporter room of the Starship Artichoke, there are always characters ready to give us what seems like thirty minutes of introductory background story and a comprehensive rundown of our mission. Unfortunately, you might mix up the fact that our sworn enemy Thoth'l, son of Thathel, has captured the Princess Thath-oth and is taking her to his lair just outside the town of Thimbar, with the fact that our trusted guide Kaboth'l has located the once powerful Sorcerer Thim-Athlothal, and has recommended that you travel to Hack-Matheth to find him. What we end up with is the vague impression that we need to find someone who is going to help us rescue someone from somewhere, and that we may need to do some fighting on the way.
I have been facetious with all of the "th" sounds, but this scenario is one that often pops up, but firing out character and location names which obviously mean nothing to the player, can strain layers as they trying to take it all in. True enough, many games that do this do not expect you to remember everything, and much of the information is meant as nothing more than supportive detail to the central plot. The problem is that players don't know this.
The second memory-related problem is exploration anxiety. As mentioned previously, the trend away from linearity towards free exploration exacts its own peculiar price on the player. This anxiety comes in two basic forms, the first of which, as mentioned before, has the player wandering aimlessly around a world, searching for something specific (or unspecified- in the worst cases), unable to remember whether or not they have been along this particular path before. Unproductive rambling can drive any player towards the escape button, but coupled with the common game-world problem that trees, corridors, paths and caves can often look the same (regularly using the same geometry), exploration can sometimes be its own worst enemy. The other form of Exploration Anxiety that most of us will be familiar with, is the nagging feeling that sometimes appears during a game, niggling at the back of your mind saying "I bet you missed one of the rooms back there", and "I bet there was a huge magic sword in it". Progressing from level to level is generally the driving force behind the gameplay, but the thought of having missed something vital, or of significant value along the way, can sometimes be detrimental.
So, what has psychology got to offer to help game designers cope with memory issues and their associated problems? I would suggest a look at the following three rules.