Sensation and perception although closely related, have distinct qualities that set them apart.

Sensation is the stimulation of a sensory receptor which produces neural impulses that the brain interprets as a sound, visual image, odor, taste, pain, etc. Sensation occurs when sensory organs absorb energy from a physical stimulus in the environment. Sensory receptors then convert this energy into neural impulses and send them to the brain.
Perception is when the brain organizes the information and translates/interprets it into something meaningful (selective attention) or something that can be made sense of or rationalized by us. Furthermore, perception is how one "receives" this feeling or thought, and gives meaning to it through memories and emotions. Perception is mainly how our brain interprets a sensation. Information is obtained through collector, receptor, transmission, and coding mechanisms. Sensation and perception compliment each other to create meanings from what we experience, yet they are two completely different ways of how we interpret our world.

The ABCs of Sensation

Sensation doesn't automatically occur; sensory processes must first convert stimulation into neural messages before any other processing can be formed. This process of transferring energy is termed transduction. For example, transduction in your ear occurs in the cochlea. It begins with the detection of stimuli by a sensory neuron, then activating receptors, and finally converting the stimuli into a nerve signal that is processed by the brain. Stimuli detectors are important because one of their abilities is to alert us to changes. They also hold authority in sensory adaptation; the absolute threshold, the terminal threshold, and the difference threshold. Sensory adaptation is the reduction of sensory responsiveness when exposed to stimulation for an extended period of time. (ex. a swimmer diving into a cold pool and eventually adapting to the temperature). However, not all stimuli can be detected. There are those sensations that we can detect are above our absolute threshold (the minimum amount of stimulation needed to produce a sensory experience).

Any stimulus that is below our absolute threshold cannot be detected. After a stimulus is over our absolute threshold, we will be able to detect it normally until it reaches the terminal threshold, where the stimulus is strong enough to be painful and cause damage. There also may be a difference in how strong or weak a stimulus is, but you can't always detect it. If a change in the intensity of a stimulus is detectable, then it exceeds our difference threshold (the smallest amount of stimulus that can be changed and detected half the time). There are three different principals dealing with JND, which are all about stimuli and detection. The first one is Weber's law, which states that the size of JND is proportional to the intensity of stimulus. So, the JND is large when intensity is high, and small when intensity is low.

One thing that affects all these things is the signal detection theory, which states that sensation depends on the characteristics of the stimulus, the background stimulation, and the detector. For instance, a person responding to a stimulus normally would be considered a "hit" in signal detection theory. However, not responding to a stimulus or responding to a non-existent stimulus is called a "miss". This can explain why thresholds vary.

How Are the Senses Alike? And How Are They Different?

Senses all operate similarly, but each receives different information and sends it to a specialized region in the brain. Therefore, different sensations occur because each sense activates a different part of the brain. The brain interprets physical energy from the outside world as nerve signals and processes them into ways that they can be used. These signals are received by the senses: 1. vision: the brain receives light waves from photoreceptors, such as rods and cones, that are transduced into neural signals that are sent away to be interpreted by the brain.s We look with our eyes but see with our brain. 2. hearing allows us, like vision, to locate objects in space. Sound waves with a certain frequency ( pitch ) and amplitude ( loudness ) are processed by the brain in the auditory cortex. 3. smell: (olfaction) odors interact with receptors in the nose which transfer a message to the olfactory bulbs located on the underside of the brain, which involves a chain of biochemical events. 4. gustation: (taste) soluble substances to flavors, and 5. skin senses: external contact to touch, warmth, and coldness. However, there are also people with disabilities to these senses, such as blindness and deafness (see Vision and Hearing ). We also have the vestibular senses and kinesthetic senses. The vestibular senses allow us to keep track of the position of our bodies and surroundings. it also enables us to keep balanced, for instance when running. Kinesthetic senses allow us to keep track of our body parts in relation to each other. We also have the ability to feel pain. The Gate-Control Theory states that we have a neural "gate" that is capable of blocking incoming pain signals. Many people can learn to control pain by psychological techniques such as the placebo effect. All of these senses transduce stimulus energy into the neural impulses.

The ABCs of Perception

When you taste pizza you are having a percept, a product of perception. Perception is the mental process that interprets and gives meaning to sensations. Color serves as an example as to how perception differs from person to person. A color may not be the same for everybody, such as red. The color "Red" to an individual might be different to another individual, but we learn at an early age that the specific color is known as "Red". Other examples include illusions and ambiguous figures. Biologically, we have these things called Feature Detectors, which are the cells in the Cerebral Cortex that specialize in taking certain features of a stimulus. The brain combines sensory details into a single percept and this unclear process is referred to as the Binding Problem. Although the binding problem has not been solved, scientists believe that it can be partially accounted for by the brain's control of the firing patterns of neurons that recognize specific elements. Bottom-Up Processing emphasizes characteristics of stimuli, rather than our concepts in their entirety and expectations. Top-Down Processing is the process of perceiving things based off of your concepts, expectations, memories, motivations, goals and information gathered over time. Perceptual Constancy is the ability to recognize the same object as remaining "constant" under different conditions.

Gestalt Psychology argues that perception is shaped by nature, or innate factors that were already built into the brain. It divides our perception into Figure and Ground. Figure is the main part of the stimuli that catches our attention immediately, and ground is the backdrop against which we perceive the figure. Our perception can also be divided into Monocular cues, cues taken from just one eye, and Binocular cues, which rely on the use of both the eyes. Closure (filling in the blanks) is an organizing process identified by Gestalt psychologists. Gestalt psychologists also recognize laws of perceptual grouping, such as the Law of Similarity, Law of Proximity, Law of Continuity, Law of Common Fate, and Law of Pragnanz. These laws are theorized to be automatically built into our brain.

Another explanation for perception was made by Hermann von Helmholtz, who recognized the role of learning, or nurture in Perception. His theory of Learning-Based Inference states that perception is mostly shaped by personal experience and inferences made through prior learning. Context, expectations, and Perceptual Set also effect Perception. ‚ÄčThe Proprioceptive Senses are Kinesthesis, Visceral Sensitivity, Vestibular Sense. The Vestibular sense is when you sense that something is moving around you, and you use your coordinated movement to stop it from moving. An example of this would be when your pencil falls off your desk, and you sense it doing so, so you catch it before it reaches the ground.

Gestalt Psychology and Helmholtz's Learning-Based Inference are not opposing viewpoints in the sense that both are needed to understand our everyday perceptions. Also, both theories require top-down processing and rely on the attention of the subject in order to meaningfully perceive a stimulus. Also, Gestalt psychologists believe that much of perception is shaped by innate factors that are built in the brain.

Although the concept of change blindness wasn't in the book, it's important to know that it's the inability to see changes in an environment. If you aren't paying attention, then you won't notice changes.


Sensation: Our senses - auditory (hearing), occipital (visual), olfactory (smell), gustation (taste), tactile (touch), kinesthetic (body position), and vestibular (balance) - register the stimulus with it's physical properties, "decode" it, and transform it into a neural signal that is then transmitted to the brain.

In the brain, the neural signal is organized and interpreted. Perception involves "making sense" of our sensations.

Sensing the warmth of a fire vs. perceiving being near the fire.
Sensing the light vs. perceiving a color (Seeing the color vs. determining what color it is)
Sensing the light reflected by an object vs. perceiving an OBJECT
Sensing the wind vs. perceiving the fan blowing on you
Sensing your cell phone vibrate vs. perceiving it is your phone
Sensing the temperature of ice cream vs. perceiving flavor
Sensing the sound vs. perceiving your music playing
Sensing the cold weather vs. perceiving
sensing the texture of the chocolate bar vs. perceiving how it tastes
it is winter
Sensing the light outside coming from the sun vs. perceiving that its warm outside
Sensing the alarm going off vs. perceiving your alarm clock.
Sensing Something that taste sweet perceiving what you're eating is cake
Sensing a loud ring vs. perceiving that its your door bell
Sensing the taste of a burger vs. perceiving that it is beef


There was an experiment about Perceptual set done by two guys named Bugelski and Alampay. Half of the people being tested were shown pictures of animals in black and white and the other half were shown pictures of humans in black and white. Then they showed every person an ambiguous picture and asked what the people saw. Most of the people that saw the animal pictures before usually said they saw a rat while the people that saw pictures of humans before usually said they saw a old man with glasses. The reason that this happened is because they were used to seeing a human or animal since they had seen so many already and this cause them to have a perceptual set on the ambiguous picture.

Fujita, K. (1997). Perception of the Ponzo illusion by rhesus monkeys, chimpanzees, and humans: Similarity and difference in the three primate species. Attention, Perception, & Psychophysics, 59(2), 284-292.

Reese,H.W.(1963)."Perceptual Set" in young children.Child Developement.151-159

Additional Resources

Quick look at bulleted notes from the textbook on Sensation and Perception

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