You must turn off your ad blocker to use Psych Web; however, we are taking pains to keep advertising minimal and unobtrusive (one ad at the top of each page) so interference to your reading should be minimal.

If you need instructions for turning off common ad-blocking programs, click here.

If you already know how to turn off your ad blocker, just hit the refresh icon or F5 after you do it, to see the page.

Psi man mascot

Chapter Four: Senses and Perception

Table of Contents

Part One: Sensation to Perception

Part Two: The Visual System

Part Three: The Auditory System

Part Four: The "Minor" Senses

Part Five: Extra Sensory Perception

Overview of Chapter 4: Senses and Perception

The running theme of this textbook is that humans have very creative brains. We assemble or synthesize our experience.

Chapter 2 argued for the fundamental point that the brain constructs mental experience. Chapter 3 discussed (among other things) some of the strange effects due to dreaming, hypnosis, and psychoactive drugs.

Now we come back down to earth. Here in Chapter 4 we see how mental constructions are made accurate, anchored in reality through the guidance of sensory processes.

The study of sensation and perception is one of the oldest specialties in psychology. The earliest psychologists believed it was logical to study sensory inputs as a first step in understanding how we built up our experience of the world.

Psychophysics is the study of how physical energy like light or sound is converted to psychological sensations. We will discuss psychophysics and its modern descendent, the Theory of Signal Detection.

Information from the environment is analyzed by sensory systems operating in conjunction with the brain. We will take a look at sense organs like the eye and the ear and how specialized sensory receptors convert physical energy into nerve impulses within the nervous system.

Recent decades have provided a few surprises, like the discovery of an extra sense organ in the nose (the vomeronasal organ). Some researchers suspect it may play a role in sexual response in humans.

Most controversial are proposals about extrasensory abilities like ESP. Starting with the research of Rhine at Duke University, many serious experimenters looked for subtle effects that might point to a previously-undiscovered "psi energy" unknown to modern physics.

Your author takes the position (common among psychologists) that forms of ESP involving forms of energy unknown to physics do not exist. At least, there is no compelling evidence that they exist.

However, people do have sensitivity to unusual forms of energy. We discuss evidence for human sensitivity to infra-red radiation, microwaves, and possibly magnetism. No doubt people have many strange ESP-like experiences, and the last part of the chapter offers possible explanations for some of them.

How this chapter is organized

We start with a section about how sensory inputs (sensation) reach the brain to be converted into perceptual constructions (perception). We discuss basic receptor types and the waveforms of light and sound.

We look at the eyeball, moving from the surface of the eye inward to the receptor layer in the retina. Then we discuss psychophysics, the oldest tradition in experimental psychology. Psychophysical curves turn out to describe very well the transduction of physical energy into nerve impulses within the sense organs.

The next section describes the auditory system, beginning with a discussion of ear structures and the processes of hearing and ending with a tip of the hat to constructive processes in auditory perception, illustrated by musical hallucinations in deafness. After that we review the other senses such as touch and taste.

The last section in the chapter is titled Extra Sensory Perception. By breaking the word extrasensory into two words, we open the door to a scientific discussion of unusual (extra) sensory capabilities that go beyond the classic seven.

We will discuss claims about ESP or psychic abilities and psychologists generally prefer non-supernatural explanations of ESP-like experiences. We review a number of non-supernatural phenomena that can produce a feeling of having ESP.

Related topics in other chapters

The sensory registers, which some psychologists want to banish from Memory chapters because they are actually sensory systems, remain in Chapter 6 (Memory) for reasons of history and tradition.

Visual scene analysis, a spin-off from computer science that grapples with the cognitive mechanisms of visual perception, is discussed in greater detail in Chapter 7 (Cognition) because it relies on some principles that are important to other forms of cognition discussed in that chapter.

Write to Dr. Dewey at

Don't see what you need? Psych Web has over 1,000 pages, so it may be elsewhere on the site. Do a site-specific Google search using the box below.