Psychology 100 Lecture 4: Sensation and Perception

Sensation

The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environments.

Perception

The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

Sensory Receptors

Are specialized neurons that detect physical stimuli in the external world.

Sensory Transduction

Is the process whereby (physical) energies captured from the external world are transformed into chemical energy that can be processed by the nervous system

Sensory Neurons

Are associated with sensory receptors; they transmit sensory information into the brain.

Light as a stimulus

The human visual system is optimized to detect a narrow band of electromagnetic (EM) spectrum that we call light.

Visible Spectrum

Light ranges between 35 nanometers (nm) and 75 nm on the EM spectrum.

What is the structure of the eye?

The eye is suspended in the orbits of the skull, attached by 7 distinct eye muscles.

What are eye movements controlled by?

Eye movements are controlled by 3 specialized cranial nerves that intervene these muscles.

Parts of the eye: 1. Scelera

Outer white covering.

Parts of the eye: 2. Cornea

Transparent part of sclera.

Parts of the eye: 3. Iris

Mascular ring that controls how much light gets in.

Parts of the eye: 4. Pupil

Hole where light enters the masjid.

Parts of the eye: 5. Lens

Focuses light on the arena.

Parts of the eye: 6. Retina

Location of sensory receptors and sensory reduction.

The Rentina and Photoreceptors:

Light that passes through the pupils travels through the eye retina, which houses the photoreceptors.

Cones

Provide us with finely detailed information about our environment.

-Used primarily in brightly illuminated environments.

-Process color.

Rods

More numerous than cones, but provide less detailed information.

-Used primarily in dimly illuminated environments

-Do not process color.

Fovea

Almost all the cones in the retina are concentrated in the fovea.

-Here visual processing is the most detailed (e.g. the highest resolution, rich in color and rich in brightness)

Optic disk

Where axons forming the optic nerve leave the eye. It contains no photoreceptors and is referred to as the “blind spot”.

Sound Wave

When air molecules to alternately condense together and pull apart, creating a sound wave.

Sound as a Stimulus

A vibrating object causes the air molecules around it to compress and decompress, creating areas of high and low pressure that correspond to the peaks and valleys of sound waves.

The Human Ear: Pinna

Collects the sound waves.

The Human Ear: Tympanic Membrane (“The Eardrum)

Membrane that transmits sound vibrations to the ossicles.

The Human Ear: Ossicles

Bones that amplify vibrations and transmit them to the cochlea.

The Human Ear: Cochlea

Location of sensory receptors and sensory transduction.

Peripheral Nervous System:

Everything outside the brain and the spinal chord.

Central Nervous System:

The brain and the spinal cord.

Automatic Nervous System:

Controls the activity of the internal organs and the glands.

Sympathetic Nervous System:

Arousal, flight or fight.

Parasympathetic Nervous System:

Rest and Digest.

Somatosensory system

Is the sensory system that is reasonable for our sensation of touch and pain.

Somatosensory Receptors:

Respond to a variety of stimulation, including:

-Pressure

-Vibrations

-Heating

-Cooling

-Tissue Damage (e.g. tearing, cutting)

Stimulation:

Of the skin bends and distorts receptors, causing ion channels to open and action potentials to be generated in nearby somatosensory neurons.

The Spinal Chord Somatosensory Receptors:

Cervical, Thoratic, Lumbar, Sacral

Cervical

Neck arms, hands and fingers.

Thoracic

Upper body (Chest and abdomen)

Lumbar

Front of legs and feet.

Sacral

Genitals and back of legs.

The Homunculus

The “homunculus” is a representation of what we would look like of the various parts of our bodies were sized in proportion of their sensitivity and drexity.

Primary Motor Cortex

Controls voluntary movement.

Prefrontal Cortex

Planning, decision making, evaluations, memory; personality characteristics.

Brocas area

Produces structured speech (generally situated in the left hemisphere only)

Primary Somatosensory Cortex:

Process information from skin senses related to body motion.

Somatosensory Association Areas:

Differentiate one object from another by touch determine the position of the objects.

Visual Associations Areas

Recognize and evaluate visual information based on past visual experiences.

Primary Visual Cortex:

Perceives Visual information

Auditory Association Area:

Differentiate one sound from another through past experience.

Primary Auditory Cortex

Perceives Sound

Wernickles Area:

Speech comprehension (generally situated in left hemisphere only)

Associate Areas

Intergate information from multiple brain regions to engage in higher -level perceptual crossing.

Psychophysics

Is the study of relationship between physical stimuli and how they are perceived.

The Gestalt School of Psychology

Was founded in the early 20th century to study how we create meaningful, ‘wholes’ out of these fragmented stimuli (e.g. the parts)

Figure and ground

When rebuilding a visual scene, our brains must first determine what to look at.

Gesalt Grouping Principles: Perceptual Grouping

There are 4 principles by which we can group:

-Closure

-Similarity

-Proximity

-Good Continuation

Closure

Our brains call upon experience with the world to fill in the gaps!

Similarity

Stimuli that are similar are perceived as being part of the same objects.

Proximity

Objects that exist near each other will be perceived as belonging each other.

Good Continuation

When viewing an object, we are more likely to see smooth continuous flowing lines rather than broken or jagged ones.

Depth Perception (Reconstructing a 3D world)

Images that fall on our retina are in two dimensions, yet we perceive the world within three dimensions.

-This ability Strats at the age of 9 months.

Monocular depth cues

Are important for perceiving death at longer distances:

-Relative Size

-Texture Gradients

-Interposition

-Linear Perspective

Interposition

An object that is partially obscured is perceived to be farther away than an object that appears to be whole or complete.

The “Ames Room” (When size consistency fails)

The Ames distorted room illusion, in which the perceived sizes of objects placed within the room differ from their objective sizes, has been used to support arguments for indirect perception.