2023-06-29 by Khushi Goel
Why Can't I Recall Smell and Touch Without Experiencing Them?
Imagine you are seated in the exam hall and the invigilator hands you the question paper. You read the first question and realize that you have studied it but can’t pin-point the right answer. You remember it was written on Page 56 in your textbook on the top right corner in a yellow box. But the word, it is just fading away.
Has this ever happened to you? If you just nodded your head and said, “Yeah, it happens all the time with me”. Worry not, because you are not alone.
We often experience hallucinations, and even “deja vu” as some people call it when your brain tricks you into thinking that you know this place, you have been here before, or you have listened to this sound before.
We have five primary senses: Sound, Vision, Taste, Smell and Touch. When we sense something by either hearing the sound of it, watching it, tasting it, smelling it or touching it, the motor neurons present in our body, send signals to the Autonomic Nervous System (ANS). These signals get temporarily stored as “Sensory Memory” and considered as Short Term Memory. An external stimulus is required to trigger the function of motor neurons into the formation of sensory memory neurons. The external stimulus could be in the form of sound waves or light rays coming from a distant object, or it could be a food particle. In order to experience a sense of taste, smell or touch, the object needs to get in physical contact with the receptors present on the respective sensory organs.
Based on the type of external stimulus, the different types of sensory memories are defined as below:
- Sound - Auditory Memory
- Vision - Iconic Memory
- Taste - Gustatory Memory
- Smell - Olfactory Memory
- Touch - Haptic Memory
A research was conducted to study the “Difference in subjective accessibility of on demand recall of visual, taste, and olfactory memories”. It was concluded that the human brain has very good access to iconic and auditory memories while very limited access to gustatory, olfactory and haptic memories. There isn't clear and concise evidence as to why this happens but one explanation has been given in the paper.
Since the external stimuli leading to the formation of iconic and auditory memory cells isn’t in direct (physical) contact with the sensory receptors present in the respective organs, the human brain is able to recollect these sensations on demand (without actually experiencing them again).
But to trigger the formation of olfactory, gustatory, and haptic memory, the external stimuli need to get in physical contact with the receptor to activate the motor neurons. Hence the human brain cannot recall a taste, smell, touch without experiencing it again. It is almost impossible for the brain to imagine a sense of smell, taste, or touch on its own without an external stimulus.
References
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5818939/
- https://healthlibrary.askapollo.com/sensory-memory-types-and-what-it-is/