Through visual perception, our brain gives sense to what the eyes identify. Perceiving is looking with interest: we look what interest us and when there is not any, perception decreases. To visually perceive is to find which things are in which place because, to guide our skiing actions, it is first required to distinguish the objects and their location in the slope. We are prone to interpret new information relating it to what we already know and this predisposes our visual perception in a certain way.
According to the Gestalt theory, when observing we first perceive the global environment and then its parts in which “the whole is more than the sum of its parts”, and that global perception facilitates the perception of the parts (Navon, 1977). For example, we perceive the slope before our first turn, the forest before the tree, the mogul field before the first bump, and the slalom course before the first gate. For this author, a visual scene analysis goes from global to local, i.e., it is decomposed rather than constructing it. To this concept, after global perceiving, we are likely to pay more attention to areas of the environment that provide further information so we can determine the necessary references.
Three-dimensional visual perception
Our brain builds three spatial dimensions as width, height, and depth. But, how do we perceive three dimensions if the retina has a two-dimensional surface? Thanks to binocular vision in which our eyes are separated about 6.5 cm (2.5 inches) on average; and because of this, each eye has different views allowing depth perception.
Visual perception of the vertical and the horizontal
Our visual system informs the verticality in which we find ourselves, in permanent comparison with the information coming from our vestibular system. If the relationship between both systems is disturbed, destabilization appears, like when skiing in flat light conditions where snow texture contrast is not fully perceived.
If vision is limited, our brain restricts signals that should be sent to our muscles. For example, in foggy conditions, we may not see the horizon, disturbing the visual perception of slope inclination, and as contrast decreases, our vestibular system makes constant adjustments. In this situation, we take the verticality of the environment as a reference, like certain lift towers, slope signs, trees, structures or other people. If we do not perceive these visual references, then we must rely on our proprioception.
Visual perception of slants
Perceiving surface orientation in which we ski is essential before moving on them. The perception of slope inclination is one of the skills we must develop when skiing. Usually, we tend to overestimate the apparent tilt while our motor performance, i.e., skiing down the slope, fits better in terms of the current slant. According to Li & Durgin (2009), the trend of overestimating inclination occurs when our gaze, just before the highest point, is almost parallel to this point. According to Proffitt et al. (1995), a slope may seem more inclined when we are standing on top of it that from below and this could be so due to our perceived difficulty towards descending it. These authors also discovered in visual perception research that descending slopes are overestimated compared to ascending ones. Proffitt (2006) proposes that slant perception is influenced by the fear of falling into potentially dangerous situations and the associated cost of being injured when descending. Ross (2010) mentions that according to the Perspective theory, the far ascending hills are perceived as more pronounced than nearby ones. He also suggests that descending hills are perceived less pronounced if we observe them from up above and further away, as from a high up cable car, that when we observe them from the plain and this is due to changes in optical images angles.
We often tend to judge a slope as more inclined as it actually is. To estimate a slope inclination by facing it, we are prone to imprecision and a better idea is to do it from a side. A slope is perceived as more inclined when we are located just before the edge but cannot see it entirely. In this case, our imagination makes us prejudge it as more inclined than it really is. Slope perception depends on our psychophysical condition, technical level, mood state, physical preparation, motivation, and on the reflection if we would be able to ski it. For example, we may perceive a slope as more difficult if we are tired.
We have a predisposition to perceive space more accurately on verticality and horizontality but with less precision on obliquity. This condition is called by Appelle (1972) as the oblique effect. Other authors also determine this phenomenon based on the fact that neurons are more numerous for detecting verticality and horizontality compared to obliquity.
Visual perception of a slope may trigger emotions of blockage before skiing down it, influencing our decisions and actions. At perceiving slope inclination, young and athletic skiers may consider it less steep that older skiers or skiers that are not in an appropriate physical shape. A way of adjusting perception to reality would be tilting one or both hands copying the slope angle.
Visual perception of forms
To interpret terrain irregularity, its forms must be visually perceived first. For example, the form of a mogul is an area that protrudes from the surface of the ground, i.e., it is the figure that sticks out and it is noticeable due to its borders. The limits of the different terrain contours stand as changes in luminosity and during flat light or fog conditions tend to dissipate, so we may perceive a white-greyish field uniformity.
According to these considerations, you can apply the following recommendations in your own skiing:
- When skiing in foggy conditions, as contrast decreases, your vestibular system will make constant adjustments. In this situation, take the verticality of the environment as a reference, like certain lift towers, slope signs, trees, structures or other people.
- Due to your perceived difficulty towards descending them, you may overestimate the slant of certain slopes.
- Bear in mind that you may perceive a slope as more difficult if you are tired.
- The visual perception of a slope may trigger emotions of blockage before skiing down it, influencing your decisions and actions. A way of adjusting your perception to reality would be tilting one or both hands copying the slope angle.
