Module 3: Sensation and Perception

In the previous module, you learned how the brain is at the center of all experiences. Yet, the brain is trapped in the skull, and cannot sense or perceive the world on its own. For the brain to function, it needs sensory information from the outside world.

Throughout the day, you encounter energy in a variety of forms: sound waves of the alarm clock that wakes you, light waves of the sun streaming through your curtains, heat, smells, and tastes of eggs cooking in a skillet. All of these examples correspond to the five basic senses that allow you to first sense, and then react to, the changing world around you.

However, there are forms of energies that exist all around you which you simply cannot sense. For example, the ultraviolet light that is outside of the visible spectrum is invisible to your eyes, but is still there, guiding bees to the right flowers, and giving people sunburns. There are sound waves too high or too low for you to hear, but at frequencies that certain other animals can detect, such as bats or whales. If you have a pet dog, he or she is likely sensing all sorts of smells that are too faint for you to detect. Many phenomena exist in the natural world that humans are not equipped to perceive, at least not without the aid of advanced equipment or technology.

In this module, you will further examine how sensation and perception combine to produce your basic experience of the world. In addition to understanding the bottom-up process of how each of the senses helps convert energy from the outside world into signals that the brain can interpret, you will also examine how famous perceptual illusions that can fool your senses. By peeling back the curtain on the basic operations of sensation and perception, you will better understand what it is that you notice, what you do not notice, and why.

Getting Started

What you see is what you get. Or is it? In this interactivity, you will explore various interpretations of a piece of art, and then determine if your initial interpretation of the image was correct. Click the player button to begin.

By completing the Photo Illumination activity, you received a taste of some key principles you will encounter in this module. When your attention was focused only on part of the image, the different colors and light combined to allow you to perceive individual items such as an onion or a bundle of grapes. In this instance, a bottom-up process occurred in which your visual sensations worked to view the colors, lines, and shadows to try and make sense of the visual information coming through the individual squares. When viewing the image as a whole, however, your brain's predisposition to spot faces instantly took over in a top-down process. In a sense, there is no man in the painting. It is really just a bunch of fruits and vegetables, but because of their clever arrangement, your brain, which has adapted to always be on the lookout for faces, instantly recognized an image that looks more like a human than a pile of vegetables.

 

Key Vocabulary

To view the definitions for these vocabulary terms, visit the course glossary.

 

absolute threshold	lens	retina
binocular cues	middle ear	rods
cones	monocular cues	selective attention
cornea	noiceptors	sensation
decibel	olfactory bulb	sensory adaptation
difference threshold	opponent-process theory	signal detection theory
figure-ground	papillae	transduction
gestalt	perception	trichromatic theory
inner ear	perceptual constancy	vestibular sense
iris	pitch	Weber's Law
kinesthetic sense	pupil