Sensations and Perceptions

By: Syed Zubyr Hussain, Leyendecker 1st


As you are currently reading this text, there is light being captured off this page that your eyes are catching. The structures in your eyes sense and convert this light into signals that are sent to your brain and create a perception in your head in the form of language. The process of transduction is defined as the conversion of incoming stimuli into neural signals. This is just one of your five sense, that in actuality, work together in order to create a whole perception. Sensation is the activation of our senses while perception is the process of understanding these sensations. Keep in mind that what we perceive is determined by what sensations are activated and by what we focus on perceiving.

Why is sensations and perceptions important?

This field of psychology is crucial to understand because it is about how the information we explain come about and how this information influences our perceptions, thoughts, and beliefs in the first place. It is the key to understanding the origin of thought. It explains the basic thought of psychology and philosophy itself.

Vision: Brief Summary

when the human eye sees something, light is actually being reflected off the stimuli and this is captured by our eye. This means that when you look at an apple, it is reflecting red light and absorbing the other colors. The color that we see depends on 2 major factors: light intensity (amount of energy the light contains) and light wavelength (the hue(color) that we see). The varying colors we see depend on the different wavelengths within the visible light spectrum. The light that was reflected first goes through our cornea (a protective covering that focuses the light), then the light goes through the pupil, which is controlled by the iris (this controls how much light enters through the pupil. The light from the pupil is then focused by the lens through a process of accommodation. From the lens, the image is flipped and projected on the retina, which is at the back of your eyeball. Transduction occurs here when the light activates the cells in the retina. The first layer of cells activated are the rods (respond to black and white) and cones (all other colors). Rods are distributed throughout the retina while cones are concentrated in the very center of the retina called the fovea. After this first layer is activated, then the bipolar cells layer is activated and after that, the ganglion cells become activated. The specific region between the optic nerve and retina where there are no rods and cones is called the blind spot. The optic nerve (the extension at the back of the eyeball from the retina to the brain) sends these neural impulses are sent to the LGN (Lateral Geniculate Nucleus) where it is then further processed to make a perception.

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David Hubel and Torsten Wiesel

What we perceive is a mixture of several features such as motion, lines, curves(feature detectors), and many more. These perception scientists revealed the pattern of organization of brain cells that process vision and how this organization relates to function. They discovered that various groups of nerve cells in the visual cortex respond differently to different types of images.

Theories of Perception

Signal Detection Theory- states that the detection of a stimulus depends on both the intensity of the stimulus and the physical and psychological state of the individual.

Top Down Processing- An alternate approach to perceiving a stimuli in which we use our prior/background knowledge to "fill in the gaps" to attain a complete perception.

Bottom Up Processing- Another approach to perceiving a stimuli in which we use the features of an object to build up a perception instead of using our past experience to perceive it.

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The picture above is an example of a figure ground relationship. To understand this, ask yourself, which part of the image is the figure and which one is the background? It's up to how you see it.

Gestalt Psychology

This field of perception describes the principles of how we perceive a group of objects. Gestalt Psychologists believe that we perceive stimuli as groups rather than isolated elements.

Closure- Figures/objects are more recognizable when they are more likely to be perceived in the same group despite there being gaps

Similarity- Objects that are similar are more likely to be perceived in the same group

Continuity- objects that have a continuous form (having a geometric pattern or trail)

Proximity- Objects close in together to one another


Our ability to maintain a constant perception of a stimuli despite changes is called constancy. There are three main types of constancy:

Size Constancy- We keep a constant size in our mind of a certain object/ stimuli and we keep that constant though we may view it smaller or bigger in size depending on our distance from that object.

Shape Constancy- We maintain a constant of the object despite viewing it from varying angles and it producing different figures/shapes.

Brightness Constancy- We perceive a constant color for the object even in varying brightness because even though it may seem like it changed color, but its actual perceived color stays the same.

The Visual Cliff Experiment

This experiment by Eleanor Gibson was used to determine depth perception and accuracy in infants. Depth cues are visual cues that are used to estimate the distance between certain objects. Gibson wanted to know if depth perception is a learned behavior or if it is something that we are born with. According to results, infants have the depth perception.

Monocular and Binocular Cues

Monocular cues are depth cues that do not require having both eyes. Such cues include linear perspective, relative size cue, texture gradient, interposition cue, and many more.

Binocular cues are depth cues that depend on having two eyes. Such cues include binocular disparity (retinal disparity) and convergence.

The Effect of Perception In General: Things to think about

Perception will vary from person to person. Not every one being sees that thought, beliefs, concept the same way as another. It is possible that one may see the general concept the same as someone else, however, when becoming specific in a approach, there will be some difference in how that being views it in respect to another. The general diction can group a schemata (mental representation of something) to be the same as how everyone else sees it, however, the diction itself I associated with different things for each person and that's what distinguishes us. We aren't the same. We are all unique in one way or the other. One has to take into consideration the way the being was raised as well as his/her morality and cultures that shape them.

Extrasensory Perception

This is often referred to as the "the sixth sense". It is claiming to have an extra sense outside the five senses such as precognition, astral projection, telepathy, clairvoyance, third eye awakening, etc. Such ESP claims, however, haven't been proved by the science committee so it is considered a "pseudoscience".

Theories of Color Vision

Trichromatic Theory

This theory explains how humans perceive color especially those of different shades. According to this theory, the human retina contains three different receptors for color where each one is most sensitive to one color. These color receptors combine the colors to produce the perception of virtually any color. There are no receptors specific to crimson red, but by stimulating specific cones in the most orderly fashion, the crimson red color is produced.

Opponent-Process Theory

A theory created by Solomon where one emotionally reacts to a stimulus which are followed by opposite emotional reactions. This theory may explain why doctors enjoy their work. First the individual will feel intense anxiety before performing a surgery and then the person will receive an opposite reaction of relief after the surgery is completed. The theory also postulates that repeated exposure to the stimulus will cause less of an initial reaction and a stronger opposing reaction. This may explain why drugs, such as opiates, give diminishing returns after prolonged use yet the effects of withdraw become more intensified and unpleasant.


Sound is made up of a series of pressures, usually of air, that can be represented as waves. Sound waves have three characteristics; amplitude, frequency, and purity where each of which is related to a psychological experience. Greater wave amplitudes are related to greater loudness; wave frequency is related to pitch; and wave purity is related to timbre.

The outer ear, the pinna, collects sound waves and funnels them through the auditory canal to the eardrum. The middle ear contains the malleus, incus, and stapes, which move and transmit the sound to the oval window, which separates the middle ear from the inner ear. After the oval window is the inner ear, whose main structure is the cochlea, snail‐like structure that has a membrane, the basilar membrane, stretched along its length. When the stapes vibrates against the oval window, the fluid in the cochlea moves and causes the basilar membrane to vibrate. The receptors for hearing, the hair cells, lie in the basilar membrane and convert the vibrations into neural impulses. The neural impulses, in turn, move along the auditory nerve to the lower brain stem and then ascend to the auditory part of the thalamus and on to the auditory cortex in the temporal lobe. Input from each ear is received on both sides of the brain.

Pitch Theories

Place Theory

Place theory is how sound is received and perceived by the human ear, this refers to how sound waves affect different areas of the tympanic membrane, or eardrum, to create the perception of different types of sounds. A similar effect can be seen by hitting a tambourine in different spots; hitting near the side gives a flatter sound that hitting it in the center.

Frequency Theory

According to this theory of how we hear sounds states that there are pulses that travel up the auditory nerve, carrying the information about sound to the brain for processing, and that the rate of this pulse matched the frequency of whatever tone you are hearing exactly. That's how we hear the tone because the pulse traveling up the auditory nerve matches the actual tone.


Gate Control Theory

The theory of pain perception was developed by Melzack where he states that the spinal cord contains a type of neurological "gate" which opens and closes to either allow or block pain signals to travel to the brain. This simply allows pain signals to pass onto the brain when they are traveling on the small nerve fibers, and does not allow pain signals to pass when they are traveling on the larger fibers. In this case, there doesn't really need to be anything physical to produce pain; you only need to have the small nerve fibers send signals onto the brain to feel pain.


As every human is developed, each create their own sensation of taste where there can be differing perception due to the way each individual is raised and the individual consistently has the same sensation until the individual adapts to other taste. For example; if you hate Tuna and you keep eating tuna eventually you will build a tolerance to it making it a part of you dietry taste and may discriminate against another food type.



Olfaction is the sense of smell. When you receive a beautiful bouquet of roses, for example, chemical compounds from the flowers travel through the air and hit your nose. Your nose then sends signals to your brain to respond to the scent of the flowers.


The term "threshold" has a couple of different meanings, but let's start with the simple one. A threshold is the minimum amount of stimulation needed to start a neural impulse. There is a very scientific explanation to this that includes the actual millivolts of the inside and outside of the neural membrane, how the sodium potassium channel works.