Sensory memory refers to the temporary storage of information based on the stimuli we receive via our senses. In other words, they are what we remember after seeing or hearing something. This process seems simple but is composed of multiple stages. First, our visual receptors see the object or characters in front of us, cause a chemical activity, start an electrical signal that reaches the neurons in the cortex of the brain. We call this process of the signal traveling from our eyes to the neurons in our brain sensory memory.
Let’s have a look at the image below.
Most people, without second thoughts, would identify the above image as ‘E’s. How do we perceive all of the characters above as ‘E’ when they all look so different?
For our brain to perceive a piece of information, it simplifies the task by analyzing what the eye sees by its component features. For example, there is a circular shape, a curve that starts from the left towards the right. After seeing the component features, our brain extracts information about the relationships between them and uses this information to identify the letter as an ‘E’ regardless of its exact size or orientation.
As such, our brain simplifies tasks into multiple steps rather than perceiving them as a whole. There are two main approaches in the process of perception, the bottom-up process, and the top-down process. The bottom-up process begins at the senses and continues in a linear fashion from one neuron to another, until information eventually arrives at the highest level of the cortex, while the top-down process is using information available at the higher levels to guide processing at lower levels. Let’s use the image below as an example.
The second letters of both the first and second words look the same, but most people see them as an ‘H’ and an ‘A’ respectively. Just like that, our brain uses various approaches to perceive and make judgments about objects.
In a study, test subjects were given sentences that had words or letters taken away or changed and were tested on how they perceive the sentences. Surprisingly, 98% of the test subjects did not notice the change in the sentences.
It is common for us to see what we expect rather than to see what we are shown. We use the prior knowledge we store and (incorrectly) see objects, and even trick our brain that we are seeing what we expect to see.
The outcome of the perception is then stored in our brain as a visual image, later leading to short-term memory.
[Reference] Lieberman, D. A. (2012). Human learning and memory. Cambridge University Press.