■ What is the primary function of our sensory receptors?

Sensory receptors transduce raw physical energy into neural impulses, which are then interpreted by our central nervous system.

What does the term absolute threshold refer to, and why is signal detection theory important?

The absolute threshold is the smallest magnitude of a stimulus that can be detected 50 percent of the time. Signal detection theory helps to separate sensitivity from motivational factors.

What is a difference threshold?

The term difference threshold refers to the amount of change in a stimulus required for a person to detect the change.

Can subliminal messages affect our behavior?

 Most careful research fails to show any meaningful effects of subliminal messages on aspects of our cognitive processes or behavior.



What are the basic structures of the eye, and what is the physical stimulus for vision?

Light rays first pass through the cornea and then enter the eye through the pupil. Adjustments to lighting conditions are executed by the iris. The lens is a clear structure whose shape adjusts to permit us to focus on objects at varying distances. Light rays leaving the lens are projected onto the retina at the back of the eyeball. The physical stimulus for vision consists of electromagnetic wavelengths that stimulate the rods and cones in the retina.

What are the basic functions of the visual system?

The basic functions of the visual system include acuity, dark adaptation, and eye movements. Acuity is the ability to see fine details. Dark adaptation is the increase in sensitivity that occurs when we move from bright light to a dim environment. Various types of eye movements are crucial to our ability to track moving objects and to perceive distance and depth.

How do psychologists explain color perception?

Our rich sense of color stems from mechanisms at several levels of our nervous system. Two leading theories that explain how we perceive color are trichromatic theory and opponent-process theory.

 ■ Why is visual perception a hierarchical process?

Visual perception is a hierarchical process because increasingly complex visual information is analyzed and compiled at successive stages—eventually yielding a coherent and flowing visual world.

What are the basic building blocks of visual perception?

The basic building blocks of visual perception begin with feature detectors—neurons in the visual cortex that respond when particular types of stimuli, with characteristic features, are detected.


 ■ What is the physical stimulus for hearing?

The physical stimulus for hearing is sound waves, which stimulate tiny hair cells in the cochlea.

 ■ How do psychologists explain pitch perception?

Place theory and frequency theory help explain how we perceive pitch.

How do we localize sound?

The “sound shadow” created by our head causes sound to reach one ear slightly faster than the other. This small time difference helps us localize the source of sound.

Touch and Other Skin Senses

 ■ What is the physical stimulus for touch?

The physical stimulus for touch is a stretching of or pressure against receptors in the skin.

 ■ Where does the sensation of pain originate?

Sensations of pain originate in free nerve endings throughout the body.

What is the basis for cultural differences in pain perception?

Cultural differences in pain perception appear to be the result of learning, not physical differences.

 ■ What role do cognitive processes play in the perception of pain?

 Negative thinking while in pain, referred to as catastrophizing, can increase the perceived intensity of pain.

Smell and Taste:

The Chemical Senses

What is the physical stimulus for smell?

The physical stimulus for sensations of smell consists of molecules that stimulate receptors in the nose. ■ Where are the sensory receptors for taste located?

The sensory receptors for taste are located in papillae on the tongue.

 ■ What are the practical benefits of using ambient pleasant fragrance to solve real-world problems?

The use of pleasant fragrances can increase alertness among persons engaged in potentially dangerous activities, such as driving.

Kinesthesia and Vestibular Sense

 ■ What information does our kinesthetic sense provide to the brain?

Kinesthesia informs the brain about the location of body parts with respect to each other.

 ■ What information does the vestibular sense provide to the brain?

 The vestibular sense provides information about body position, movement, and acceleration.

Perception: Putting It All Together

Why is selective attention important?

Selective attention reduces interference from irrelevant sensory sources.

Why is it important to consider sensation and perception in the development of warnings?

 The effectiveness of warnings depends on both sensory and perceptual processes.

What role do Gestalt principles play in perceptual processes?

 The Gestalt principles of perceptual organization help us to structure the input from our sensory receptors.

What are perceptual constancies?

 Perceptual constancies are principles describing our ability to perceive aspects of the world as unchanging despite variations in the information reaching our sensory receptors, such as information about size, shape, or brightness.

■ What are illusions?

 Illusion is a term used by psychologists to refer to errors in interpreting sensory information.

 ■ What are the bottom-up and top-down theories of pattern recognition?

The bottom-up theory suggests that pattern recognition stems from our ability to recognize and combine basic visual features. In contrast, top-down theory emphasizes the role that expectations play in shaping our perceptions.

What are geons? What is their role in object recognition?

Geons are basic cylindrical shapes that, when combined according to rules, can be used to form any object. Some evidence suggests that geons are the basis of our representation of objects in memory.

How are we able to judge depth and distance?

Judgments of depth and distance result from both monocular and binocular cues.


 ■ How are the concepts nature and nurture related to perception?

 Both nature and nurture are important determinants of the ways we perceive the world around us. Nature refers to genetic influences on perception, whereas nurture refers to the relative effects of the environment and learning.

Extrasensory Perception: Perception without Sensation?

 ■ How do most psychologists view the possibility of extrasensory perception or psi?

Most psychologists remain highly skeptical about its existence and await the results of further careful research.