How does sensation occur

For example, consider holding a five-pound weight the reference level , and then having a one pound weight added. However, if you hold a fifty pound weight the new reference level , you would not be likely to notice a difference if one pound is added. The absolute threshold is the minimum volume of the radio we would need in order to notice that it was turned on at all.

However, determining the just-noticeable difference, the amount of change needed in order to notice that the radio has become louder, depends on how much the volume has changed in comparison to where it started. Sensory adaptation is the decrease in the responsiveness of a sensory system that is confronted with a constant stimulus. Sensory adaptation, also called neural adaptation, is the change in the responsiveness of a sensory system that is confronted with a constant stimulus. This change can be positive or negative, and does not necessarily lead to completely ignoring a stimulus.

One example of sensory adaptation is sustained touching. When you rest your hands on a table or put clothes on your body, at first the touch receptors will recognize that they are being activated and you will feel the sensation of touching an object. However, after sustained exposure, the sensory receptors will no longer activate as strongly and you will no longer be aware that you are touching something. These corpuscles rapidly change and adapt when a stimulus is added. Then they quickly decrease activity, and eventually cease to react to the stimulus.

When the stimulus is removed, the corpuscles regain their sensitivity. For example, the constant touch of clothes on our skin leads to our sensory adaptation to the sensations of wearing clothing. Notice that when you put an article of clothing on, after a brief period you no longer feel it; however you continue to be able to feel other sensations through it.

This is because the additional stimuli are new, and the body has not yet adapted to them. In contrast, sensitization is an increase in behavioral responses following repeated applications of a particular stimulus.

Unlike sensory adaptation, in which a large amount of stimulus is needed to incur any further responsive effects, in sensitization less and less stimulation is required to produce a large response.

For example, if an animal hears a loud noise and experiences pain at the same time, it will startle more intensely the next time it hears a loud noise even if there is no pain. There are many stimuli in life that we experience everyday and gradually ignore or forget, including sounds, images, and smells.

Sensory adaptation and sensitization are thought to form an integral component of human learning and personality. Privacy Policy. Skip to main content. Sensation and Perception. Search for:. During light adaptation , a large number of rods and cones are bleached at once, causing us to be blinded for a few seconds. Light adaptation happens almost instantly compared with dark adaptation. Interestingly, some people think pirates wore a patch over one eye in order to keep it adapted to the dark while the other was adapted to the light.

Our cones allow us to see details in normal light conditions, as well as color. We have cones that respond preferentially, not exclusively, for red, green and blue Svaetichin, This trichromatic theory is not new; it dates back to the early 19th century Young, ; Von Helmholtz, This theory, however, does not explain the odd effect that occurs when we look at a white wall after staring at a picture for around 30 seconds.

Try this: stare at the image of the flag in Figure 3 for 30 seconds and then immediately look at a sheet of white paper or a wall. According to the trichromatic theory of color vision, you should see white when you do that. Is that what you experienced? This is where the opponent-process theory comes in Hering, This theory states that our cones send information to retinal ganglion cells that respond to pairs of colors red-green, blue-yellow, black-white.

These specialized cells take information from the cones and compute the difference between the two colors—a process that explains why we cannot see reddish-green or bluish-yellow, as well as why we see afterimages.

Color deficient vision can result from issues with the cones or retinal ganglion cells involved in color vision. Some of the most well-known celebrities and top earners in the world are musicians. Our worship of musicians may seem silly when you consider that all they are doing is vibrating the air a certain way to create sound waves , the physical stimulus for audition.

People are capable of getting a large amount of information from the basic qualities of sound waves. The amplitude or intensity of a sound wave codes for the loudness of a stimulus; higher amplitude sound waves result in louder sounds.

The pitch of a stimulus is coded in the frequency of a sound wave; higher frequency sounds are higher pitched. We can also gauge the quality, or timbre , of a sound by the complexity of the sound wave. In order for us to sense sound waves from our environment they must reach our inner ear. Lucky for us, we have evolved tools that allow those waves to be funneled and amplified during this journey.

Initially, sound waves are funneled by your pinna the external part of your ear that you can actually see into your auditory canal the hole you stick Q-tips into despite the box advising against it. During their journey, sound waves eventually reach a thin, stretched membrane called the tympanic membrane eardrum , which vibrates against the three smallest bones in the body—the malleus hammer , the incus anvil , and the stapes stirrup —collectively called the ossicles.

Both the tympanic membrane and the ossicles amplify the sound waves before they enter the fluid-filled cochlea , a snail-shell-like bone structure containing auditory hair cells arranged on the basilar membrane see Figure 4 according to the frequency they respond to called tonotopic organization. Depending on age, humans can normally detect sounds between 20 Hz and 20 kHz.

It is inside the cochlea that sound waves are converted into an electrical message. Because we have an ear on each side of our head, we are capable of localizing sound in 3D space pretty well in the same way that having two eyes produces 3D vision.

Have you ever dropped something on the floor without seeing where it went? Did you notice that you were somewhat capable of locating this object based on the sound it made when it hit the ground? We can reliably locate something based on which ear receives the sound first. What about the height of a sound?

If both ears receive a sound at the same time, how are we capable of localizing sound vertically? After being processed by auditory hair cells, electrical signals are sent through the cochlear nerve a division of the vestibulocochlear nerve to the thalamus, and then the primary auditory cortex of the temporal lobe.

Information from the vestibular system is sent through the vestibular nerve the other division of the vestibulocochlear nerve to muscles involved in the movement of our eyes, neck, and other parts of our body. This information allows us to maintain our gaze on an object while we are in motion. Disturbances in the vestibular system can result in issues with balance, including vertigo.

Who actually enjoys having sand in their swimsuit? Somatosensation —which includes our ability to sense touch, temperature and pain—transduces physical stimuli, such as fuzzy velvet or scalding water, into electrical potentials that can be processed by the brain. Tactile stimuli —those that are associated with texture—are transduced by special receptors in the skin called mechanoreceptors. Just like photoreceptors in the eye and auditory hair cells in the ear, these allow for the conversion of one kind of energy into a form the brain can understand.

After tactile stimuli are converted by mechanoreceptors, information is sent through the thalamus to the primary somatosensory cortex for further processing. For example - one of the most well known Gestalt principles is the Phi Phenomenon, which is the illusion of movement from presenting stimuli in rapid succession. When you see a cartoon or running Christmas lights, you see movement although none actually exists because of this principle.

When we look at an object, we see that object figure and the background ground on which it sits. For example, when I see a picture of a friend, I see my friends face figure and the beautiful Sears brand backdrop behind my friend ground. However, the idea of "good form" is a little vague and subjective. Most psychologists think good form is what ever is easiest or most simple. There are simply 3 elements from my keyboard next to each other, but it is "easy" to organize the elements into a shape that we are familiar with.

Objects that are close to each other in physical space are often perceived as belonging together. As you probably guessed, this one states that objects that are similar are perceived as going together. Dots in a smooth curve appear to go together more than jagged angles. This principle really gets at just how lazy humans are when it comes to perception. For example, when you see geese flying south for the winter, they often appear to be in a "V" shape.

For example, the picture of two faces looking toward each other that is also a vase. I am sure most every Introductory Psychology book has this example. You know the artist, Escher who draws the pictures like Pain is an unpleasant yet important function for survival: warning system but not all pain is needed for survival. There are two different pathways to the brain on which pain can travel - information brought from free nerve endings in the skin to the brain via two different systems:.

For example - child birth: Lamaze method falsely leads us to believe it won't be painful. Maybe if we know it will be bad we can adequately prepare to handle it. For example - study manipulated moods of subjects then asked them to complete questionnaires of pain perception. Those in negative mood group reported significantly more pain than other subjects. So, it can be opened to allow pain through or closed to prevent pain from being perceived.

The Gate - actually a neural network controlled by the brain. Located in an area of the spinal cord called the Substansia Gelatinosa. There are two types of nerve fibers in this area:. So why is the process of raising sensitivity to light to adapt to darkness more complex than lowering sensitivity to adapt to light? Caruso has suggested that a more gradual process is involved in darkness adaptation due to humans tendency over the course of evolution to slowly adjust to darkness as the sun sets over the horizon.

There is another factor that affects sensation and perception: attention. Attention plays a significant role in determining what is sensed versus what is perceived.

Imagine you are at a party full of music, chatter, and laughter. You get involved in an interesting conversation with a friend, and you tune out all the background noise. If someone interrupted you to ask what song had just finished playing, you would probably be unable to answer that question. One of the most interesting demonstrations of how important attention is in determining our perception of the environment occurred in a famous study conducted by Daniel Simons and Christopher Chabris In this study, participants watched a video of people dressed in black and white passing basketballs.

Participants were asked to count the number of times the team in white passed the ball. During the video, a person dressed in a black gorilla costume walks among the two teams. You would think that someone would notice the gorilla, right? Because participants were so focused on the number of times the white team was passing the ball, they completely tuned out other visual information.

Failure to notice something that is completely visible because of a lack of attention is called inattentional blindness. More recent work evaluated inattention blindness related to cellphone use. Participants were not aware that while they walked through the square a unicycling clown would ride right in front of them. After the students reached the outside of the square they were stopped and asked if they noticed the unicycling clown that rode in front of them.

Cell phone users were found to walk more slowly, change directions more often, pay less attention to others around them and were also the most frequent group to report they did not noticed the unicycling clown.

David Strayer and Frank Drews additionally examined cell phone use in a series of driving simulators and found that even when participants looked directly at the objects in the driving environment, they were less likely to create a durable memory of those objects if they were talking on a cell phone.

This pattern was obtained for objects of both high and low relevance for their driving safety suggesting little meaningful cognitive analysis of objects in the driving environment outside the restricted focus of attention while maintaining a cell phone conversation. Additionally, in-vehicle conversations did not interfere with driving as much as cell phone conversations as Strayer and Drews suggest, drivers are better able to synchronize the processing demands of driving with in-vehicle conversations compared to cell-phone conversations.

Overall it is apparent that directing the focus of our attention can lead to sometimes serious impairments of other information, and it appears cell phones can have a particularly dramatic impact on information processing while performing other tasks.

In a similar experiment to the activity above, researchers tested inattentional blindness by asking participants to observe images moving across a computer screen. They were instructed to focus on either white or black objects, disregarding the other color.

Motivation can also affect perception. Have you ever been expecting a really important phone call and, while taking a shower, you think you hear the phone ringing, only to discover that it is not? If so, then you have experienced how motivation to detect a meaningful stimulus can shift our ability to discriminate between a true sensory stimulus and background noise.

This motivational aspect of expectation in conversation additionally may be why such strong inattentional blindness has been found in relation to cell phone use. The ability to identify a stimulus when it is embedded in a distracting background is called signal detection theory.

Signal detection theory: A theory explaining explaining how various factors influence our ability to detect weak signals in our environment. Signal detection theory also explains why a mother is awakened by a quiet murmur from her baby but not by other sounds that occur while she is asleep.