Paranormal reports sometimes include mentions of things seen in 'corner of the eye', occasionally as part of a wider haunting. Typically, the phenomena are fleeting and usually vanish if witnesses turn to look straight at them. They are generally reported to look like shadows, often resembling faces or human figures. For this reason they are often called 'shadow ghosts' or 'shadow people'. Some people even think they represent some kind of 'demon' or other strange entity.

Corner of eye phenomena

Before we can consider whether such 'corner of the eye' phenomena might be paranormal, we need to understand what to expect from the normal operation of our peripheral vision.

Here is a picture to illustrate how your peripheral vision can change the way things look. It may produce different results depending on your computer screen, the illumination in your room and your own visual system (ie. from eyes to brain). So nothing is guaranteed!

Start by look well to the right of the picture above so that it is barely visible. Note how you cannot see any shape in detail and probably no colours either. Now rotate your head leftwards very slowly, always staring directly forward, so that you are aware of more and more of the photo. Gradually shapes and colours in the photo should become more distinct and obvious. Eventually, when looking just to the right of the photo you may become aware of an apparent face. The 'face' will probably vanish as you finally stare directly at the photo. Don't worry if you don't see the face! We are all different and some people will see it while others will not.

The 'face' is seen in profile, looking rightwards. Probably the best place to stare is at the tiny red flower about half way up the photo and about one quarter of the way from the right edge of the frame. Stare at the flower and the large 'face', if you see it at all, should appear to the left. Try looking from different distances and the 'face' may pop out. Even if you don't see a face, you may well see part of the picture (the lighter portion of the in-focus bit) appear to 'pop out' from the rest.

Some people may even see a face when looking directly at the photo. Others won't see a face at all at any time during this exercise. Either way, the experiment should still demonstrate that peripheral vision of complex shapes and colours, like those in the photo, is poor. You only really see the details photo well when looking directly at it. Using peripheral vision increases the chances of seeing 'faces' and 'figures' in random patterns.

The area where we have a clear detailed view of anything is surprisingly small. To demonstrate this, stare at one word in the middle of this paragraph. Without changing where you are staring, how many words can you read on either side, above and below? The answer is, not very many at all!

Peripheral vision

So how come the 'picture in your head' looks so detailed if we can only see such a tiny area in high resolution? The answer is that our eyes constantly more about rapidly (saccades), scanning the scene ahead. Then our brains assemble the 'picture in our heads' from the recent scans. For much more on this important topic, see common misperceptions.

Outside the central area of the 'picture in our head', there is much lower resolution. Being used to it, you probably don't even notice this. Peripheral vision is produced largely by retinal rod cells. Unlike the cone cells that produce the central detailed views, rods have poor resolution.

Rods are more sensitive to light and movement than cones but cannot see colour. Multiple rod cells converge into a single interneuron cell. This reduces overall resolution, like merging several pixels into one on a TV picture, but improves sensitivity to movement. This poor resolution and high sensitivity to movement is what causes everyday 'corner of the eye' phenomena, where you are vaguely aware of something in your peripheral vision but cannot see it properly.

Rods insensitivity to colour and poor resolution means that corner of the eye phenomena are typically black and white and their shapes vague. If you turn to look at an object seen in the 'corner of your eye', you will start to see it in much greater detail and in colour. As a consequence, it will look completely different. What was a vague dark shadow in the corner of your eye will turn into a differently shaped object in full colour. Sometimes the difference will be so pronounced that the original object will appear to vanish!

Due to the in-built human propensity to see faces and figures in random shapes, it is inevitable that some corner of the eye phenomena include such shapes. Once we turn to look at them properly, they will no longer make sense as figures or faces. Our brains will then 'rationalise' that the face or figure has vanished! It is no wonder that witnesses think they have seem a ghost or 'shadow person'.

Furthermore, our brains may 'substitute' objects that are not seen well, such as those seen in the peripheral vision, with similar things from our visual memory. These 'visual substitutions', which occur before we are consciously aware of what we're seeing, can appear strikingly real. Such 'substitutions' are not limited to just faces and figures, though these are common.

Distance is difficult to judge in peripheral vision, partly due to a lack of details and also because some objects may only be visible in one eye (no stereopsis) due to the nose intruding! The distance of objects seen in peripheral vision may thus often be wrongly reported. Something nearby may appear further away or vice versa. In particular, a nearby small object can appear bigger and further away. Naturally, the effect disappears when you turn to look directly at the object. So a 'large object' (seen as a 'ghost') in the middle distance 'vanishes', leaving only a small bush nearby!

Shadow ghosts

Of course, some people believe that shadow people and shadow ghosts exist as genuine paranormal phenomena. There are reports of shadow ghosts seen when looking straight ahead. Here is an account of shadow ghost case which does not appear to involve corner of the eye phenomena. One possible explanation for shadow ghosts seen in direct vision is actual shadows!

However, where shadows are seen only in peripheral vision, the explanation given above must certainly be considered. If people are convinced that they are living in a haunted house, they may notice such natural phenomena more acutely than usual, sensitised to the idea by psychological suggestion.

An interesting point about shadow ghosts is that many are typically seen to be moving (if they weren't they probably wouldn't be noticed). There are motion illusions, related to peripheral vision, that may account for certain specific sightings. The 'peripheral drift illusion' occurs when you observe an object with alternating black and white (and sometimes grey) lines (or rectangles), or something resembling that situation. When such objects are observed in the peripheral vision, anomalous motion may appear. In 'real life' cases this might occur in a semi-dark situation with fence posts, railings, stair banister spindles or wheels, particularly if they are painted white. The illusion is thought to be caused by the way our brains detect motion in our visual fields. See here for probable real life case.

Night vision

In low light, our retinal cone cells do not work and we rely on our rods. This means that the world can look radically different to the one we know from normal daylight vision. One problem, though, is that rods need time to adapt to reach maximum sensitivity in low light (some 30-45 minutes to get to 80% of full sensitivity). Even once you have adapted to night vision there are more problems to consider.

• poor resolution - object shapes are not see well and can be misinterpreted
• no colours visible - objects tend to resemble either shadows or white lights
• a shift in sensitivity towards the blue end of the spectrum (in the Purkinje Effect)
• autokinesis (small stationary objects appear to move if you stare at them)
• night blind spot - best eyesight resolution is 15 - 20 degrees off centre*
• poor depth perception
• poor ability to see exactly where moving objects are
  

These significant changes in vision in low light can help explain many apparent paranormal phenomena seen in low-light as examples of misperception. In particular, this also applies to investigation vigils held in the dark.

Low light misperception

The various visual impairments brought about by low light conditions inevitably increase the possibility of misperception. Such misperception, as in the daylight version, can be affected by psychological suggestion. So holding a dark vigil in an allegedly haunted building is almost bound to produce spurious reports of paranormal phenomena.

In particular, the night blind spot means that objects seen straight ahead look fuzzy compared with those seen at a slight angle (say 15 - 20 degrees off centre). In daylight, we see objects straight ahead best so there is a tendency to do the same at night. It means, however, that objects may easily be misperceived by staring directly towards them. This fact alone may account for many reports of ghosts in low light conditions.

Small moving lights are quite frequently reported on vigils. The lights could be produced by LED indicators, for instruments or domestic appliances, or from light thrown on walls from gaps in curtains or under doors. Whatever causes such lights, if you stare at them in the dark, they will usually appear to move! This is autokinesis and it may be responsible for reports where people claim to have seen 'orbs' with the naked eye.

Though night vision allows good perception of movement, it is more difficult to say exactly where a moving object is in low light.

The fact that everything appears black or white in low light can also give rise to shadow ghosts or ghostly white figures.

Finally, the lengthy time required by eyes to adapt to low light means that for long periods people may see very little at all. Such 'sensory deprivation' can sometimes lead to hallucinations.

Unfortunately, these factors typically combine a dark vigil. In typical vigils, divided up into several 'dark' sessions separated by well-lit breaks, night vision adaptation times are a real problem. For much of the time investigators will not be able to see anything much even when it is there to be seen. For these reasons, dark vigils are of limited value for scientific evidence.

* because central vision is dominated by the cone-rich fovea which doesn't work in low light

Further oddities

If you look at something red straight ahead, you are more likely to notice red objects in your peripheral vision at the same time (though objects in peripheral vision still look black and white). You will also notice the motion of all red objects in your visual field.

This could explain why some objects in our peripheral vision may become more noticeable, even when they don't change or move. It is bound up in something called attentional focus. It is just another oddity of the way our perception works that could explain certain anomalous observations.

© Maurice Townsend 2009