Sensation and Perception

The process by which our sensory receptors respond to light, sound, odor, textures, and taste, and transmit that information to the brain

Sensation

Our eyes, ears, nose, tongue, and skin comprise an:

Elaborate sensory system

Job of elaborate sensory system which our eyes, ears, nose, tongue and skin comprise of:

Receive and process information from the environment

Each sense organ contains:

Receptors

Receptors are:

Specialized cells

Function of receptors:

Detect and then convert light waves, sound waves, chemical molecules, and pressure into neural impulses that are transmitted to the brain

When adults are totally deprived of sensory input for long periods of time, they experience:

Hallucinations and impaired efficiency in all areas of intellectual functioning

The process by which the brain actively selects, organizes, and assigns meaning to incoming neural messages sent from sensory
receptors

Perception

Example of how sensation is different from perception:

From a sensory point of view, the American flag is a mass of red, white, and blue colors and horizontal and vertical lines. Perception is the process by which you interpret these splotches of color and array of lines as the American flag

The process by which sensory receptors convert the incoming physical energy of stimuli such as light waves into neural impulses that the brain can understand

Transduction

Profession of Philip Zimbardo:

Psychologist

What did Philip Zimbardo say about transduction?

It is a "process” that “seems so immediate and direct that it fools us into assuming that the sensation of redness is characteristic of a tomato or the sensation of cold is characteristic of ice cream."

Sensations such as "red" and "cold" occur only when:

The neural impulses reach the brain

The minimum amount of a stimulus that an observer can reliably detect at least 50 percent of the time

Absolute threshold

Example of absolute threshold:

The human visual system can barely detect a candle flame at a distance of about 30 miles on a clear, dark night

The minimal difference needed to notice a stimulus change

Difference threshold

The difference threshold is also called the:

“Just noticeable difference”

JND stands for:

Just noticeable difference

Example of difference threshold:

Anika is trying to study for an AP Psychology test on sensation and perception. However, she can't concentrate because her brother is watching an episode from The Mandalorian and has the volume turned up at full blast. Anika asks Akash to "please turn the volume down so I can study!" Akash responds by lowering the volume by one notch.
If Anika notices this minimal amount of change, it qualifies as a just noticeable difference.

The difference threshold can cause:

Problems

Example of how the difference threshold can cause problems:

Kyle has a difficult time tasting the difference between a little and a lot of sugar. As a result, he adds too much sugar into his brownie mix causing the brownies to be too sweet.

Profession of Ernst Weber (1795-1878):

German Psychologist

Ernst Weber observed that:

The just noticeable difference will vary depending on its relation to the original stimulus

According to Weber's law:

The size of the just noticeable difference is proportional to the strength of the original stimulus

For the average person to perceive their difference, two objects must differ in weight by:

2 percent

Example of Weber’s Law:

A weight lifter who is bench pressing 50 pounds would notice the addition of a 5-pound weight. However, the same weight lifter would not notice the extra 5 pounds if he were bench pressing 500 pounds.

The traditional theory of thresholds assumed that a signal would be sensed when:

It is intense enough to exceed one's absolute threshold

The traditional theory of thresholds assumed that a signal would be missed when:

It is below our threshold

The traditional theory of thresholds did not take into account:

The characteristics of the perceiver

Example of how the traditional theory of thresholds does not take into account the characteristics of the perceiver:

Anika noticed the change in volume when Akash turned his TV down one notch because she was trying to concentrate and was focused on the TV's distracting noise. Had Anika been exchanging text messages with a friend, she would not have noticed the change in volume.

Signal detection theory assumes that:

There is no single absolute threshold

According to the signal detection theory, a detection depends upon:

A combination of stimulus intensity, background noise, and a person's physical condition, biases, and level of motivation

Example of signal detection theory:

A sentry in wartime will likely detect fainter stimuli than the same sentry in peacetime

What do psychologists do when applying signal detection theory to experiments?

Sort the trials into one of four categories

What are the 4 categories that psychologists sort the trials in experiments applying the signal detection theory?

If the signal is present, the person can decide that it is present or absent. These outcomes are called hits or misses. It the signal is absent the person can still decide that the signal is either present or absent. These are called false alarms or correct rejections.

Sensory adaptation occurs when:

A constant stimulus is presented for a length of time

What happens when a constant stimulus is presented for a length of time?

Sensation often fades or disappears

Why does sensation often fade or disappear when a constant stimulus is presented for a length of time?

Receptors fire less frequently

Examples of sensory adaptation:

When a jogger first puts on a new pair of running shoes, he or she immediately notices that the new shoes have a different feel from the old shoes. However, after going for a jog, he or she no longer notices the new shoes.

When a swimmer first dives into a pool he or she immediately notices that the water is chilly. However, after swimming a few laps, he or she no longer notices the water temperature.

When an employee works in an Italian restaurant, he or she immediately notes the pungent aroma of garlic. However, by the end of the day the employee no longer notices the aroma.

Does sensory adaptation affect vision?

No

Why does sensory adaptation not affect vision?

Receptor cells in the eyes always receive continuously changing stimuli

Why do receptor cells in the eyes always receive continuously changing stimuli?

Our eyes constantly shift from one location to another

Our most complex and most important sense

The visual system

What does the visual system do?

Transduces light waves into neural messages that the brain

What does the brain do with neural messages transduced from light waves by the visual system?

Process into what we consciously see

Light waves from the outside world first enter the eye through the:

Cornea

A clear membrane covering the visible part of the eye:

Cornea

Function of the cornea:

Protects the eye and helps gather and direct incoming light waves

The small opening in the middle of the iris

Pupil

The pupil changes size to:

Let in different amounts of light

How does the pupil let in different amounts of light?

By changing size

The colored part of the eye

Iris

The iris is a:

Ring of muscle tissue

The iris controls:

Size of pupil

How does iris control size of pupil?

By contracting and expanding

The muscles in the eye respond to:

Light and to inner emotions

When do pupils constrict?

When we are in parasympathetic calm

When do pupils dilate?

When we are in sympathetic arousal

A transparent structure located behind the pupil that actually focuses and bends light as it enters the eye

Lens

The change in the curvature of the lens that enables the eye to focus on objects at various distances

Accommodation

A visual acuity problem that results when the cornea and lens focus on an image in front of the retina

Nearsightedness

Result of cornea and lens focusing on an image in front of the retina:

Distant objects appear blurry

A visual acuity problem that results when the cornea and lens focus on an image behind the retina

Farsightedness

Result of cornea and lens focusing on an image behind the retina:

Objects near the eye appear blurry

The light-sensitive membrane at the back of the eye

Retina

The retina contains:

Millions of sensory receptors for vision

The transduction of light waves into neural messages occurs in the:

Retina

Photoreceptors in the retina that are especially sensitive to dim light but not to colors

Rods

Rods allow you to:

See in poorly lit environments

Do cats or humans have better night vision?

Cats

Why do cats have better night vision than humans?

They have a higher proportion of rods to cones

Location of rods in relation to retina:

Away from center of retina

Rods are responsible for:

Peripheral vision

Photoreceptors in the retina that are especially sensitive to colors and to bright light

Cones

Cones cannot detect color well in:

Dim lights

Cones are concentrated in the:

Fovea

Small region in the center of the retina:

Fovea

Visual acuity is greatest in the:

Fovea

Images that do not fall on the fovea tend to be perceived as:

Blurry or indistinct

Specialized neurons that connect the rods and cones with the ganglion cells

Bipolar cells

Specialized neurons that connect to the bipolar cells

Ganglion cells

The bundled axons of the ganglion cells form the:

Optic nerve

Order of processing visual information:

Rods and cones → bipolar cells → ganglion cells → optic nerve

The point where the optic nerve leaves the eye and where there are no rods or cones

Blind spot

Are we normally aware of the blind spot?

No

Why are we normally unaware of the blind spot?

Because our eyes are moving and the brain fills in the missing information

Components of the retina:

Rods, cones, bipolar cells, ganglion cells, blind spot

The optic nerve carries visual information to:

Visual cortex

The visual cortex is part of the:

Brain

Location of visual cortex:

Occipital lobe at the back of brain

Job of visual cortex:

Process and interpret visual information

Examples of visual information that the visual cortex processes and interprets:

Faces and expressions

The human visual system can identify approximately ______ different color combinations

7 million

______ theory(s) describe how color vision works at different stages of the visual process

Two

The two theories that describe how color vision works at different stages of the visual process:

Trichromatic and opponent-process theory

Trichromatic theory is also called:

Three-color theory

The trichromatic theory begins with the fact that:

There are three primary colors -red, green, and blue

How can any color be created from the three primary colors?

By combining the light waves of these three colors

When did Hermann von Helmholtz propose that the eye must have color receptors that correspond to the three primary colors?

Mid-nineteenth century

Profession of Hermann von Helmholtz:

German physicist