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Sensation and Perception Cheat Sheet (DRAFT) by

Sensation and Perception ch-1 cuet prep 2024

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Sensation

Sensation
refers specif­ically to the stimul­ation of our sensory organs.
 
physical things in the world stimulate our sensory organs.
 
occurs when special receptors in the sense organs—the eyes, ears, nose, skin, and taste buds—are activated, allowing various forms of outside stimuli to become neural signals in the brain.
 
This process of converting outside stimuli, such as light, into neural activity is called transd­uction.

Sensory Thresholds

Ernst Weber
did studies trying to determine the smallest difference between two weights that could be detected.
Weber's Law
of just noticeable differ­ences (jnd, or the difference thresh­old). A jnd is the smallest difference between two stimuli that is detectable 50 percent of the time, and Weber’s law simply means that whatever the difference between stimuli might be, it is always a constant.
Gustav Fechner
expanded on Weber’s work by studying something he called the absolute threshold
Absolute Threshold
is the lowest level of stimul­ation that a person can consci­ously detect 50 percent of the time the stimul­ation is present.
Subliminal Stimuli
Stimuli that are below the level of conscious awareness
 
These stimuli are just strong enough to activate the sensory receptors but not strong enough for people to be consci­ously aware of them. Many people believe that these stimuli act upon the uncons­cious mind, influe­ncing behavior in a process called subliminal percep­tion.
Formula
ΔI/I = k
 
where ΔI represents the smallest noticeable differ­ence, I represent stimulus intensity, and k is known as Weber’s constant

Signal Detection Theory

Definition
Signal Detection Theory is a psycho­phy­sical model that explains how humans make decisions based on sensory inform­ation.
 
based on the idea that indivi­duals may pick up on meaningful inform­ation, known as “signals,” from noisy and ambiguous stimuli.
 
is used when psycho­logists want to measure the way we make decisions under conditions of uncert­ainty, such as how we would perceive distances in foggy conditions
Four Outcomes
Hit
A hit occurs when the observer correctly detects the presence of a signal and responds, “yes.” It is considered a correct response
Miss
A miss occurs when the observer fails to detect the presence of a signal and responds “no” when the signal is actually present. It is considered an incorrect response.
False Alarm
A miss occurs when the observer fails to detect the presence of a signal and responds “no” when the signal is actually present. It is considered an incorrect response.
Correct Rejection
A correct rejection occurs when the observer correctly detects the absence of a signal and responds, “no.” It is considered a correct response.
 

Sensory Receptors

Sensory Receptors
are specia­lized forms of neurons, the cells that make up the nervous system.
 
Instead of receiving neurot­ran­smi­tters from other cells, these receptor cells are stimulated by different kinds of energy—for example, the receptors in the eyes are stimulated by light, whereas the receptors in the ears are activated by vibrat­ions. Touch receptors are stimulated by pressure or temper­ature, and the receptors for taste and smell are triggered by chemical substa­nces.
 
Each receptor type transduces the physical inform­ation into electrical inform­ation in different ways, which then either depola­rizes or hyperp­ola­rizes the cell, causing it to fire more or to fire less based on the timing and intensity of inform­ation it is detecting from the enviro­nment.

Habitu­ation and Sensory Adaptation

Habitu­ation
Some of the lower centers of the brain filter sensory stimul­ation and “ignore” or prevent conscious attention to stimuli that do not change. The brain is primarily interested in changes in inform­ation.
 
Although they actually are hearing it, they aren’t paying attention to it.
 
it is the way the brain deals with unchanging inform­ation from the enviro­nment.
Sensory Adaptation
is another process by which constant, unchanging inform­ation from the sensory receptors is effect­ively ignored.
In habitu­ation, the sensory receptors are still responding to stimul­ation but the lower centers of the brain are not sending the signals from those receptors to the cortex.
The process of sensory adaptation differs because the receptor cells themselves become less responsive to an unchanging stimul­us—­garbage odors includ­ed—and the receptors no longer send signals to the brain.

Vision