When you see a red light at a traffic signal, your sensory receptors detect the light, but your brain interprets this as a signal to stop, based on your prior knowledge of traffic rules. This process where raw sensory information is transformed into meaningful understanding is known as perception.
Perception is a fundamental cognitive process that allows us to interpret and make sense of sensory information from the environment. It involves not just receiving raw data but processing it to form a meaningful experience. This process bridges the gap between sensation (the raw data our sensory organs collect) and cognition (our thoughts, memories and understanding) Without perception we would lack the ability to make sense of our environment and make decisions accordingly. This mental process becomes a huge part of cognitive psychology considering its impact on our decision-making process, thinking, understanding and also experiences.
Stages of Perception
Perception occurs in these distinct stages.
Sensation: This is the initial stage where sensory organs like the eyes, ears and skin detect stimuli
Attention: The selection of relevant stimuli for further processing, while irrelevant stimuli are filtered out.
Organisation: The brain organises the incoming data by recognizing patterns of familiar structures
Interpretation: Finally, the brain interprets the organised data based on past experiences, context and knowledge, giving it meaning.
Example: When walking in a park, you may hear a bird singing (sensation), decide to focus on it (attention), recognize the pattern of the bird’s song (organisation), and identify it as a robin based on your previous experiences (interpretation).
Types of Perceptual Processing
There are two ways in which information can be accessed by the brain and how the data which is consumed from the environment is articulated. These are:
Bottom-up processing
Bottom-up processing is the most basic form of perception, where understanding starts with sensory output itself. This process is data-driven, meaning that perception begins with the raw data that our senses receive from the environment, and then builds upward toward a higher level of understanding. The brain processes this information in real-time, without relying on prior knowledge or expectations.
Example: Imagine you’re walking through a forest and see a tree you’ve never encountered before. The brain starts by processing the visual input: the tree’s shape, colour, size and many more. You don’t immediately recognise the type of tree because you have no prior knowledge o, so your brain works from the bottom up, analyzing the features and characteristics to form a basic understanding of the object in front of you.
Infants extensively use this form of perceptual processing since they have no prior knowledge or experience of the outside world. They use their sensory output to receive information and process it accordingly.
The bottom-up processing is vital when encountering unfamiliar stimuli, as it helps build a detailed perception without biases or expectations that might otherwise cloud your interpretation. However, bottom-up processing can be slow, as it requires the brain to methodically interpret each sensory input bit by bit.
Top-down processing
In contrast, top-down processing is conceptually driven, where perception is guided by prior knowledge, expectations and experiences. This process allows the brain to interpret sensory information more efficiently by filling in gaps or recognising familiar patterns. Rather than building from the sensory data itself, top-down processing works by using existing knowledge to shape how we perceive the stimuli.
Example: When reading a jumbled sentence like “Ths is a t_est”, you can quickly recognise it as “This is a test” without needing to analyse each letter in detail. Your brain fills in the gaps based on your knowledge of language and context. Similarly, when you see a partially obscured stop sign, your experience with road signs allows you to recognise it immediately, even if part of the sign is hidden from your view.
Top-down processing makes perception faster and more efficient because it allows us to skip some of the slow, methodical stages involved in bottom-up processing. However, this efficiency can come at a cost: it can sometimes lead to perceptual errors or biases. When our expectations are too strong, we might misinterpret or overlook details that don’t align with our assumptions.
While we understand that these are two types of processing, they also work hand in hand in most situations. While bottom-up processing provides a foundation by gathering sensory information, top-down processing uses prior knowledge to quickly make sense of that information. These processes are not mutually exclusive but complementary.
An example of this would be when you walk into a restaurant, bottom-up processing might help you identify unfamiliar objects or food items on the menu, while top-down processing allows you to quickly recognise common elements like tables, chairs and structure of the menu based on your previous experiences and restaurants.
The balance between the two is dynamic and context-driven. Based on the need of the situation, bottom-up or top-down processes play different roles in different situations and may pose them being prioritised at different levels.
Components of Perception
Here are several components of perception we come across in our daily lives:
Perceptual Set and Expectations
Perception is not always objective, it is shaped by our expectations and experiences, a concept known as the perceptual set. This refers to the tendency to perceive stimuli in a particular way, influenced by emotions, expectations and cultural experiences. For example, if you’re in a dark alley at night and hear a sound you perceive it as a threat rather than it being a bustle of leaves due to your previous experiences of being in that situation or due to the media coverage in your neighbourhood.
Depth Perception and Visual Cues
Depth perception is what allows us to view the world in a three-dimensional space, even though our retinas only retrieve images as two-dimensional. This is accomplished through binocular cues and monocular cues. These cues help us understand the coverage of the area, the difference between the images in both eyes, the objects’ sizes and many more. For example, when you’re driving a car, you can gauge the distance between your car and the others’ using your monocular cues of size consistency and other forms of the cues. Even though a car farther down the road looks smaller, you know it hasn’t shrunk, it’s just farther away.
Illusions
Perceptual illusions reveal the limits and biases of our perception. This occurs when our brain misinterprets sensory information, leading to a distorted or misleading perception of reality. Illusions highlight the shortcuts our brain takes to process information efficiently. One well-known example is the Müller-Lyer illusion, where two lines of equal length appear to be different because our brain interprets the arrowheads as depth cues, making one seem longer than the other.
Other illusions like optical illusions and colour constancy illusions, showcase how our brains can be tricked into misinterpreting visual information which reveals the intricacies and limits of our processes.
Perception is a complex cognitive process that goes beyond simply seeing this world. It involves sensation, attention, organisation and interpretation to create a meaningful understanding of our environment. From the influence of our prior knowledge and expectancies to the cues used to perceive, perception is an essential function of cognition that shapes our everyday experiences. However, perception is not infallible, as demonstrated by phenomena like optical illusions. Understanding the complexities of perception helps us deepen our understanding of making sense of the world around us.