Perception

By perception, we mean the ability of a human to identify the source and nature of that which has stimulated the senses in some way. While some researchers use the term perception as a synonym for sensation, I prefer the more general, and I believe more accurate, sense of the term.  The distinction between sensation and perception can be understood as the difference between smelling something sweet and understanding that the source of the smell is a flower. It’s the difference between feeling a painful jab in one’s finger and noticing that the source of the unpleasant sensation is a thorn. It’s the difference between tasting something very tart and realizing that the source of the taste is a lemon.

Through sensation we test the world, albeit often unconsciously, using our senses to gather information about the environment in which we live. We test to see if objects are in proximity to us at the present moment. We smell food to see if it’s edible. We test to see (often to our regret) whether an object is useful or harmful by touching it. Through perception we try to determine what we have sensed, and more broadly, the context in which we have sensed it. While sensation is fundamental and comparatively uncomplicated, perception is much more complex, and as we will see, is marked by frequent errors.

Our perception of the world is limited by physical constraints. In ordinary circumstances, that is, unaided by any special technology, we cannot observe the world of the four fundamental forces of nature directly, and therefore cannot perceive them. We see only their effects, and it would not occur to us that these phenomena existed had not their presence in the Universe been elucidated over a very long period of time by those possessing very specialized forms of training and knowledge. Similarly, we do not see (unaided) the molecular, atomic, and subatomic worlds these fundamental forces organize, and thus cannot draw perceptual conclusions about them. Our ordinary visual sensory apparatus is indeed capable of seeing very small things, but the worlds of the smallest objects are orders of magnitude smaller than even the tiniest visible objects. At the other end of the scale, we can see but cannot comprehend the largest objects and structures in existence. Such objects can only be analyzed, again, by specialists. It can be said therefore that most humans exist, perceptually, in a sort of middle realm, where both the most diminutive and the most expansive objects elude us.

The larger significance of perception is the fact that it so often is the basis of judgment in humans. Many humans have an aversion to statistical data and other forms of empirical evidence. They are often willing to form judgments based on their perception of a situation, and their perception of it alone. Disquietingly often, that perception is incomplete or even completely erroneous. Everyone realizes at some point that perception is a flawed instrument. In visual perception, for example, a number of issues arise. Very often, there is a difference between what we see and what we think we see or what we expect to see. The human brain fills a great deal of information in when we look at something, in order to make our current visual experience congruent with our previous experience. Many visual distortions, optical illusions, mirages, and hallucinations exist which demonstrate this clearly, although it can be argued that we are aware of (and thus not fooled by) many of them. Human hearing is limited in significant ways as well, as humans are the inferiors of such animals as dogs in that department.

So let’s examine perception more deeply, keeping in mind that our own perceptions may hinder such an examination.

Definitions of Perception

As is the case with any complex subject, there are distinct schools of thought that have arisen around the subject of perception. In the nineteenth century the German scientist Hermann von Helmholtz did pioneering research in this area. In Helmholtz’s view we learn how to perceive:

In his sign theory of perception as expressed in his early career (1848–1868), Helmholtz argues that the mind makes a series of mental adjustments, “unconscious inferences,” to construct a coherent picture of its experiences. Helmholtz argues that spatial position, often used as a criterion to individuate objects, is an interpretation of our sensations, and not their immediate result. Again, stereoscopic vision shows that what may appear, to us, as a single image is in fact two images resolved into one. Perspective can distort size, as when one puts a finger in front of the moon. Helmholtz believes that we learn how to interpret spatial concepts through experience, which means that he has what he calls an empirical theory of spatial perception.¹

Building on Helmholtz’s work, the cognitive psychologist Richard Gregory often focused on visual perception in order to make larger points about perception in general. He observed that the images we receive in the retina are largely ambiguous and don’t tell us about several significant properties of the objects we’re seeing (their temperature, their weight, and so on). As we acquire greater knowledge of the objects we encounter, we are more able to make hypotheses about the properties of these objects. We unconsciously predict the characteristics of objects, therefore. These hypotheses and predictions allow us to go beyond basic sensory experiences and reflexes. Moreover, Gregory pointed out that “any afferent nerve signals the same quality or sensation whatever stimulates it.” Colors, for example, can come not only from light the eyes receive but by mechanical or electrical stimulation. He added, “It was clear to [Isaac] Newton that it is strictly incorrect to say that light is coloured. Rather, light evokes sensations of colours in suitable eyes and brains.”²

The late psychologist Irvin Rock divided hypotheses about perception into three different categories. He summarized them as follows:

The Inference and Empiricist Perspective. First elucidated by British empiricist philosophers such as John Locke and David Hume, these thinkers argued that at birth the human mind was a tabula rasa (a blank slate), and that knowledge could only be obtained through sensory experience. It was the task of the mind to learn how to interpret these sensations, which was done through association. In this view, humans learned to associate certain sensations with particular objects or visual perspectives. Helmholtz enlarged on these ideas, as we saw above, by introducing the idea of unconscious inferences and the role that experience plays in perception.³

The Gestalt Perspective. This view was first developed by Rene′ Descartes and later by Immanuel Kant. Descartes asserted that the mind was not a blank slate and that it possessed innate concepts about the properties of the objects it encounters. Kant held that the mind possesses the ability to mentally put objects in their respective positions and put events in chronological order. In the early 20^th century many psychologists adopted and expanded upon this view. The Gestaltist concept can be said to embrace this idea: The whole is greater than the sum of its parts (which to me represents a nod to the reality of synergy). To the adherents of Gestalt ideas, the brain has the innate ability to organize disparate sensory information into units of meaning. The Gestaltist would argue that the brain can perform this operation spontaneously, without the need for prior experience.⁴

The Stimulus Perspective. Researchers working in what is called the psychophysical tradition reject the proposition that the senses, in particular sight, are incapable of causing perception unless aided by experience or the mind’s innate ability to organize stimuli in a synergistic fashion. In this perspective specific kinds of stimuli evoke specific kinds of perception. In this view, the modern form of which is most closely associated with James J. Gibson, perceptions are responses to physical stimuli, and these responses come in many varieties.⁵

It was Rock’s opinion that each of these interpretations has errors. It was also his belief that perception is a synthesis that incorporates elements of each view.⁶

Can we broaden the concept of perception to include not only immediately perceivable stimuli, but also larger issues, such as our perceived role in a given situation or our perceived place in life?

There is considerable debate at present as to whether, or to what extent, our perceptual processes are cognitively penetrable: that is, affected by higher-level processes of attention, expectations, emotions, and knowledge. Recent evidence suggests that the so-called low-level aspects of perception are relatively unaffected by these factors but if our definition of perception involves the detection of affordances—what the world offers us—then it seems undeniable that attention, expectations, and emotions are all involved and affect our behaviour.⁷

I am presently limiting the examination of perception to phenomena linked to the senses in real time, but I acknowledge that the broader usage of the term is useful. This broader usage is, however, more applicable to issues related to a human’s standing in what might be called the social order, which we will examine in more detail in another volume of this work.

Neural Correlates of Perception

Any assessment of the neural correlates of perception naturally involves a discussion of the correlates of consciousness itself. (Please see the discussion in the chapter The Emergence and Nature of Human Consciousness, Part One: Toward a Definition of Consciousness.) One team of neuroscientists investigating this matter sees two competing schools of thought. The first believes that sensory information reaches the level of awareness when it is shared with various systems within the brain, such as those involved in memory and action planning, or in those brain mechanisms involved in reality-monitoring. In this concept subconscious processing takes place in the brain’s sensory regions while conscious processing is handled by the networks in the frontoparietal region of the brain. The competing view is that conscious awareness is processed by the brain’s sensory regions. In this view the perceptual experience of vision, for example, is handled by feedback loops such as those in the thalamocortical system. (Please see the discussion in the chapter Some (Brief) Comments On the Brain’s Anatomy and Physiology.) These feedback processes cause “information to reach awareness even if that information is never accessed by higher-order cognitive mechanisms.”⁸

There is research that indicates that what is known as rivalrous visual stimuli, the conflicting images that are conveyed by the eyes to the retina, cause a response in many different regions of the cortex. In the experiments on this phenomenon it did not matter whether the subjects used were consciously perceiving the stimuli or not. Other experiments involving stimulus of the scalp indicated that subjects who were consciously aware of the stimulus had a stronger neural response than those subjects who were not aware.⁹

Research on the neural correlates of facial perception suggests that the human brain has highly specialized resources to handle this task and that humans seem particularly sensitive to the appearance of other humans’ faces. A research study on this question explains why this area of inquiry is so crucial:

Faces represent a special object category in human perception. Face perception has evolved in humans to be highly specialized and efficient reflecting the central role that faces play in social interactions and communication. The perception of faces is the primary information source for the recognition and identification of specific individuals, is critical for interpreting expressions and emotions, and underpins the extraction of important social cues; hence, impaired visual or visual-cognitive perceptual systems can severely challenge social engagement.¹⁰ 

Now let us turn to examining crucial features of our perceptual system.

Aspects of Perception

Percepts

Percepts are that which is perceived. More precisely:

The mental representation of something that is perceived, an object or image as perceived by the senses rather than the physical stimulus that generates it, distinct from both the proximal stimulus and the distal stimulus.¹¹

In short, we form an idea in the mind when we have perceived something. That idea is a conclusion, perhaps tentative, about what our senses have detected. The larger issue with percepts is whether they are veridical, i.e., whether we can trust that our inner representations of them reflect the reality of the outer world, or if we can assume that others perceive what we perceive.

We tend to believe percepts, especially those springing from eyesight, to be objectively real, that they reflect the outer nature of the world accurately. This impression tends to be strengthened if more than one of our senses is involved in this evaluation. However, it is crucial to once again emphasize the point that we perceive a mediated version of reality. Moreover, we must, in ordinary circumstances, rely on what might be called a perceptual consensus. Other people must confirm our percepts. But even then, this doesn’t mean that we know the physical properties of the objects we perceive. That would require much more active investigation. As we saw in the last volume, there are percepts we cannot experience because our physical faculties won’t permit it (as in the case of our inability to imagine what the ultrahigh frequencies dogs experience sound like). And our perceptions are affected by age, as our sensory acuity diminishes.¹²

Perceptual Constancies

Perceptual constancy is the ability to identify an object’s characteristics, such as its color or dimensions, under different viewing conditions, such as a change of vantage point or different lighting. However, if the changes of condition are drastic enough (such as the way certain lighting can affect blue/green perception), if the context in which something is seen is radically unfamiliar, or if an individual is seeing an object for the first time, perceptual constancy can break down or be absent in the situation.

Shared Perceptions

Often perceptions take place within a social context. We are in a group of people, for example, all witnessing a particular event. Shared experiences and shared understandings are the subjects of what psychologists, philosophers, anthropologists, and other researchers call intersubjectivity. Interestingly enough, valuable insight into shared perceptions is being gleaned from studies on how to make robots more humanoid in function. One team of researchers premised their research findings by first stating:

Human perception is based on unconscious inference, where sensory input integrates with prior information. This phenomenon, known as context dependency, helps in facing the uncertainty of the external world with predictions built upon previous experience. On the other hand, human perceptual processes are inherently shaped by social interactions. … If using previous experience – priors – is beneficial in individual settings, it could represent a problem in social scenarios where other agents might not have the same priors, causing a perceptual misalignment on the shared environment.¹³

In short, since people bring different (and unique) sets of knowledge and experience to any given situation, their perceptions will not only be different, but might actually conflict. These researchers ultimately conclude that our awareness that others’ perceptions differ from our own is a key element in the development of empathy. This awareness also affects social interaction. Moreover, sociality, the human tendency to form groups and communities, may be affected by the way humans adjust to the awareness of differing perceptions.

Subliminal Perception

There is evidence that a great deal of perception takes place below the level of conscious awareness. Since the brain itself evolved before consciousness emerged fully, it may be said that its ability to monitor the environment around it could hardly have been anything but subliminal. In fact, it is probable that humans perceive more subliminally than they do consciously. The effect of deliberately-constructed subliminal suggestions is still an area of controversy in perception research, but it is far less controversial to say that humans react to a great deal of which they are not consciously aware.¹⁴ In fact, the odd sense that someone is watching them that so many people sometimes experience may be attributable to nonconscious vision. We are seeing without realizing we are seeing.¹⁵

Misperceptions

As we saw, humans tend to see their perceptions as reflective of the reality in which they are immersed. But there are myriad ways that humans can misperceive what is going on around them. Sensory misperceptions are quite common. Optical illusions, auditory hallucinations, tactile hallucinations in which people sense stimuli that simply aren’t present, distortions of the sense of taste or smell, are all major causes of perceptual errors. (For a much fuller discussion see the chapter in this section called Brain Tricks and Cognitive Biases.) People who are plagued by mental illnesses of various kinds are often prone to chronic misperceptions as well. Add up enough sensory misperceptions and it is possible for a human (or group of humans) to utterly misperceive the larger situation in which they find themselves.

Then there are misperceptions simply due to the unfamiliarity of the percept. If we are seeing or hearing something utterly new to us, for example, we will tend to be more unsure of how it should be described. The more unfamiliar something is in our experience, the greater the chance of misperception. If we encounter an object that is, to us, completely novel, we may not understand what it does (or if it has any purpose at all) or where it came from. Even if we are merely unsure of what we are sensing, that alone can lead to perceptual errors.

The Effect of Emotion on Perception

Although perception and emotion are usually studied as separate subjects, research has shown that emotion has a significant impact on how we perceive stimuli. Vision is affected by fear, sorrow can make us more vulnerable to optical illusions, intense goal-oriented emotions can alter our perception of the size of objects, and physical challenges can be affected by how we perceive the environment around us (such as seeing the steepness of a mountain). Research indicates that emotion influences perception far more than we might suspect, and that cognition, emotion, and perception are strongly interactive. Fear causes us to more readily perceive potential threats, positive feelings reinforce our belief in the course we are on, negative emotions encourage us to change paths. Objects that are significant to us or with which we have strong associations may appear larger.¹⁶

Other research indicates that stimuli that carry emotional significance for us are more accurately identified, more readily processed perceptually. As one team of researchers put it:

The exact mechanisms responsible for this enhanced processing have not yet been identified. However, several lines of research indicate that the amygdala is involved in the modulation of the perceptual encoding of emotionally significant stimuli.

They stress that long-term memory and the impact of past experiences may also be implicated in the rapidity of perceptual processing.¹⁷

Another team of researchers emphasizes the brain’s need to prioritize the torrent of sensory information flooding into it. It is their conclusion that the more emotionally relevant a stimulus is, the more readily it will be perceived since the brain treats it as a priority. Such stimuli will generally cause a human to be more intensely engaged and less distracted as well. Examinations of the brain regions involved in perceptual processing appears to support this conclusion. And as other researchers have found, the amygdala plays a crucial role in this processing.¹⁸

Other Issues

As we noted in the chapter on sensation, color has been shown to have an effect on the way we see the world. Significant research has been done on the effect of color on perception, and indeed such research stretches back to the 19^th century. Recent research indicates that color can have an effect on student performance, the perception of pain, the perception of the size of a room or other space, and mood, among others.

Research on the development of color preferences in adults has given us additional insight. American and British adults tend to like blue the best and yellow-green the least. There is evidence that colors associated with objects people like tend to be preferred. Studies of British and Chinese women reveal they are drawn to red and green more than men.¹⁹

Many people are convinced of the reality of extra-sensory perception, but as yet there is no scientific evidence of its existence. Many ordinary events are interpreted as ESP episodes simply because people tend to have a poor grasp of odds and chance. (See the chapter entitled Randomness, Probability, and Coincidence in Volume One.) But in all honesty, it is my personal opinion that such phenomena exist. They do not appear to be amenable to ordinary methods of experimentation, and I understand those who doubt their existence. But even after 99% of events have been explained, there are still those which cannot be. I believe that someday ESP’s reality will be confirmed. But that day is not yet here.

So sensation lets us detect the world. Perception helps us interpret what we have detected. Now we will examine how we try to learn from what we have detected and interpreted. We will now turn to the subject of cognition. In doing so we will begin to see the true dimensions of the universe inside us.