Perception doesn’t just happen. It is the end result of complex “behind the scenes” processes, many of which are not available to our awareness.
Why is the psychology of perception important?
Understand how other basic cognitive processes (attention, memory, thought, language, etc.) work, and understand the mind in a holistic way.
Develop medical applications to treat perception or language-related diseases (e.g. agnosia, chronic pain, dyslexia, etc.).
Determine and evaluate the perceptive requirements to carry out regulated activities (driving, use of weapons, flying a plane, etc.).
Develop devices to restore or optimize a process (vision or hearing loss).
Neuropsychology and neuropsychological rehab.
Perception
📔 Neuropsychology is the study of the behavioral effects of brain damage in humans. It aims to understand the relationship between the brain and behavior, focusing on the effects that injury or anomalous brain functioning may have on cognitive, emotional, and behavioral processes and personality.
📔 Perception happens when our brain transforms electrical signals representing a stimulus in its experience. Some processes involved in perception are the organization, analysis, and integration of sensory information by the brain.
It is a basic pillar upon which superior cognitive processes lie (memory, learning, reasoning, thought, etc.). Our perception informs us about the properties of our environment that are important for our survival, and it helps us interact with the environment. Our different perceptual processes create a (visual, auditory, tactile) representation of our mind’s environment, creating awareness of what surrounds us, which allows us to act appropriately within it.
Important!
Perception is the gathering point between the physical and mental world.
Our perceptive experience takes place in our brain –not in any sensory organ of our body.
These two statements raise some interesting questions…
Does reality match our cognitive representation of it?
Is the information that our organs grasp and convey reliable and accurate?
Most researchers categorically agree that there is a physical world and, to a more ambiguous extent, they seem to agree that there is a certain consistency (although not always) between the information issued by physical energy and our psychological experience.
We need to factor in, not only the information from the stimulus and the context, but also our previous experiences and knowledge, motivations, inferences, expectations, etc. These all add up information and help us build our perceptive world.
Sensory Receptors
📔 The sensory system is a complex neural network of pathways that relay information about the external environment between the brain and the body. Sensory receptors pick up data about external stimuli and transmit that information as electrical signals to the spine and brain.
Pinillos (1975) classified the different sensory systems based on the type of information they provide.
Exteroceptors are the sensory receptors that respond to stimuli originating from the outside of the body. They monitor the external environment. Exteroceptors correspond to the five senses we all know (sight, hearing, smell, taste, and touch). We get the most information out of our visual system, and its stimulus is light, electromagnetic energy in the form of light waves. Our hearing system also plays a crucial role in our interaction with the environment, since it’s the bases of our main communication system: language. Its stimulus is sound waves.
Interoceptors respond to stimuli arising within the body such as chemical stimuli, deep pressure, and many others (located deep within the body, in the viscera). They monitor the internal environment.
Proprioceptors respond to muscle or tendon stretch and help the body monitor body position (body sense, vestibular system).
📔 A sensory receptor is a specific physiological pathway through which we capture, transform, and transmit (to the brain) a type of energy or specific stimulus.
Sensory quality refers to the type of stimuli that a certain sensory receptor is able to capture. The sensory quality of the sight (eye) is light, that of hearing (ears) is sound, etc.
Sensation
📔 Sensation is the process by which a stimulus or information is captured by sensory organs or senses before it receives any meaning. It occurs when sensory receptors detect sensory stimuli.
Perceptions, on the other hand, require organizing and understanding the incoming sensation information. In order for sensations to be useful, we must first add meaning to those sensations, which create our perceptions of those sensations.
Sensations allow us to see a red burner, but perceptions entail the understanding and representation of the characteristic hot.
Perceptual Process
The perceptual process is a sequence of processes that work together to determine our experience of and reaction to stimuli in the environment. Following the diagram shown by Goldstein (2011), the process can be divided into four categories: Stimulus, Electricity, Experience and Action, and Knowledge.
Stimulus refers to what is out there in the environment, what we actually pay attention to, and what stimulates our receptors.
Electricity refers to the electrical signals that are created by the receptors and transmitted to the brain.
Experience and Action are our goals. We want to be able to perceive, recognize, and react to stimuli.
Knowledge refers to the information we previously had and bring to the perceptual situation, and it can affect many different steps in the process.
📔 A stimulus is all of the things in our environment that we can potentially perceive. It is any form of energy or signal that can activate or stimulate the cells of sensory organs and to which we can respond (in an observable or non-observable way). It exists both “out there,” in the environment, and within our body.
📔 Information, from a cognitive perspective, is a set of stimuli or energy that reaches a sensory organ.
Steps in the perceptual process
The environmental stimulus is all of the things in our environment that we can potentially perceive.
When we focus on something, making it the center of her attention, it becomes the attended stimulus. The attended stimulus changes from moment to moment, as we shift our attention from place to place.
Stimulus on receptors. When we focus our attention on something and look directly at it, this creates an image of the object and its immediate surroundings on the receptors of our retina. Once the object has been transformed into an image, we can describe this image as a representation of the object.
Transduction is the transformation of one form of energy into another form of energy. It occurs in our nervous system when energy in the environment is transformed into electrical energy.
Transmission. Once the image has been transformed into electrical signals in our receptors, these signals activate other neurons, which in turn activate more neurons. Eventually, these signals are transmitted to the eye (if signals don’t reach the brain, there is no perception!).
Processing involves interactions between neurons. The original electrical representation of the stimulus that is created by the receptors is transformed by processing into a new representation of the stimulus in the brain.
Perception is conscious sensory experience. It happens when the electrical signals that represent a specific object are transformed by our brain into our experience of seeing that object.
Recognition is our ability to place an object in a category. Did you know people with agnosia are unable to recognize objects? Perception and recognition are different and they happen in separate processes, but not independently.
Action includes motor activities such as moving the head or eyes and locomoting through the environment. Many researchers consider action as part of the perceptive process because it is important to our survival, and ultimately, the first objective of perception was to guide the action of organisms.
Types of stimuli
Distal stimuli are objects and events out in the world around us. They are physical energy that comes from the outside world.
Proximal stimuli are the patterns of stimuli from these objects and events that actually reach your senses (eyes, ears, etc.). They are the projection (or first representation9 of the stimulus energy on our sensory receptors.
💡 Important notes!
Not all electromagnetic energy from the distal stimuli reaches the eye. Part of it is lost due to some optical structures of the eye.
We are not able to perceive all the stimuli out there. For example, the human eye can only detect wavelengths from 400 to 700 nanometers.
The proximal image appears upside down and smaller than the distal stimuli.
The proximal image is 2D. While the distal image is 3D.
The proximal image is partially controlled by the observer (through head and eye movements).
The information about an object reaches the eye as electromagnetic energy, but it is transmitted to the brain through bioelectrical impulses.
Bottom-up processing and top-down processing
Knowledge isn’t always involved in perception, although it often is (even if we sometimes are not aware of it). Bottom-up and top-down processing often work together to create perception.
Bottom-up processing
Bottom-up processing (also called data-based processing) is processing that is based on incoming data. Incoming data always provide the starting point for perception because, without incoming data, there is no perception. In our moth example, the incoming data are the patterns of light and dark on our retina created by light reflected from the moth and the tree.
Bottom-up processing is essential for perception because the perceptual process usually begins with the stimulation of the receptors.
Top-down processing
Top-down processing (also called knowledge-based processing) refers to processing that is based on knowledge. Taking our previous example, this knowledge includes what we know about moths.
As stimuli become more complex, the role of top-down processing increases.
How to Approach the Study of Perception
The goal of perceptual research is to understand each of the steps in the perceptual process that lead to perception, recognition, and action. To accomplish this goal, perception has been studied using two approaches: the psychophysical approach and the physiological approach. Cognitive influences need to be taken into consideration in both approaches.
Psychophysical approach
The psychophysical approach to perception was introduced by Fechner in the 1960s. He coined the term psychophysics to refer to the use of quantitative methods to measure relationships between stimuli (physics) and perception (psycho).
Physiological approach
The physiological approach to perception involves measuring the relationship between stimuli and physiological processes and between physiological processes and perception. These physiological processes are most often studied by measuring electrical responses in the nervous system, but can also involve studying anatomy or chemical processes.
The Mind-Body Problem
How do physical processes such as nerve impulses or sodium and potassium molecules flowing across membranes (the body part of the problem) are turned into the richness of perceptual experience (the mind part of the problem)?
What is the relationship between thought and consciousness in the human mind, and the brain as part of the physical body?
Researchers have identified many connections between neural firing and experience. This kind of research focused on determining connections between stimuli and the firing of neurons is often referred to as research on the neural correlate of consciousness (NCC), where consciousness can be roughly defined as our experiences. Now, the NCC may solve part of the problem, but just the easy part.
One thing is to identify the correlation between physiological responses and experience. Knowing how physiological responses cause experience is something else.