Chapter 8 Sensation Perception Sensation Perception Sensation What

Chapter 8 Sensation & Perception

Sensation & Perception • Sensation – What occurs when a stimulus activates a receptor. • Perception – The organization of sensory information into meaningful experiences.

Psychophysics • The study of the relationships between sensory experiences and the physical stimuli that caused them.

Thresholds • Absolute threshold – The weakest amount of a stimulus that a person can detect half the time. • Difference threshold – The smallest change in a physical stimulus that can be detected between two stimuli. • Also known as the JND

Approximate absolute thresholds for the 5 senses: • Vision - Candle flame seen at 30 miles on a clear, dark night. • Hearing - Tick of a watch under quiet conditions at 20 feet. • Taste - 1 Teaspoon of sugar in 2 gallons of water. • Smell - 1 Drop of perfume diffused into a threeroom apartment. • Touch - A bee's wing falling on your cheek from 1 centimeter above.

Weber’s Law • For any change in a stimulus to be detected, a constant proportion of that stimulus must be added or subtracted.

Sensory Adaptation • Your senses are most responsive to increases and decreases, and to new events rather than to ongoing, unchanging stimulation.

The Stroop Effect

THE EYE Video

How do we interpret sensations? • STIMULUS - energy that affects what we do. • RECEPTORS – specialized cells that convert environmental energies into signals for the nervous system.

The Structure of the EYE • PUPIL – an adjustable opening that regulates the amount of light entering the eye. • IRIS – the colored structure on the surface of the eye.

The Structure of the EYE • CORNEA – a rigid transparent structure on the outer surface of the eyeball. • LENS – a flexible, transparent structure in the eye that changes its shape to focus on the retina.

The Structure of the EYE • RETINA – a layer of visual receptors covering the back surface of the eyeball.

The RETINA contains 2 types of receptors: • Rods – Black & white vision – Work best at night – 125 million • Cones – Color vision – Work best in daylight – 7 million

The Structure of the EYE Optic Nerve – the nerve that carries impulses from the retina to the brain.

The Structure of the EYE • Blind Spot – The point where the optic nerve exits the eye and where there are no photoreceptors. Also on page 216.

Interactive

The Detection of Light • ELECTROMAGNETIC SPECTRUM – the continuum of all the frequencies of radiated energy. • Visible light, what human eyes can see, is only a small part of the entire spectrum.

Color Deficiency • Color deficiency inability to distinguish one color from another.

Binocular Cues • Binocular Fusion – The process of combining the images received from the 2 eyes into a single image. • Retinal Disparity – The differences between the images stimulating each eye.

Nearsighted vs. Farsighted Video Clip

Process of Hearing • Video Clip

Hearing • Auditory Nerve – The nerve that carries impulses from the inner ear to the brain, resulting in the perception of sound.

Deafness • Conduction Deafness – Hearing loss that results when the bones connected to the eardrum fail to transmit sound waves properly to the cochlea.

Deafness • Nerve Deafness – Hearing loss that results from damage to the cochlea, the hair cells, or the auditory nerve.

Balance • Vestibular System – Three semicircular canals that provide the sense of balance, located in the inner ear and connected to the brain by a nerve.

3 Semicircular Canals

The Vestibular Sense • If you spin hard enough and then suddenly stop, the tiny current keeps going for a little bit, which gives you the sensation that you are still spinning, but in the opposite direction. • Your brain may try to compensate for this, and cause you to fall or at very least feel dizzy.

Olfaction • Sense of smell. • Smell can influence mood, memory, emotions, mate choice, and the endocrine system (hormones).

Smell • Olfactory nerve – The nerve that carries smell impulses from the nose to the brain.

TASTE • The sensory system that responds to chemicals on the tongue. • Taste Buds – The site of the taste receptors, located in the folds on the surface of the tongue.

TASTE RECEPTORS • • Sweet Salty Sour Bitter • Umami?

TASTE & SMELL • Our sense of smell is responsible for about 80% of what we taste. • Without our sense of smell, our sense of taste would be limited. • Our sense of smell becomes stronger when we are hungry.

Skin Senses • Skin senses include pressure on the skin, warmth, cold, pain, vibration, movement across the skin, and stretch of the skin. The skin has 3 types of sensation: 1. pressure 2. temperature 3. pain

The Gate Control Theory • Pain messages must pass through a gate, probably in the spinal cord, that can block these messages.

Body Senses • Kinesthesis – The sense of movement and body position. – Receptors in the muscles, tendons, and joints.

PERCEPTION

Sensation & Perception • Sensation – What occurs when a stimulus activates a receptor. • Perception – The organization of sensory information into meaningful experiences.

Figure and Ground • An object and its background.

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Gestalt Psychology The whole is greater than the sum of its parts.

The Gestalt Laws of Perceptual Grouping Proximity Continuity Similarity Simplicity Closure video clip

The Gestalt Approach • Proximity – we tend to group objects together when they are near each other.

The Gestalt Approach • Continuity – we prefer perceptions of connected and continuous figures to disconnected and disjointed ones.

The Gestalt Approach • Similarity – we tend to group similar objects together in our perceptions.

The Gestalt Approach • Simplicity – we see the simplest shapes possible.

The Gestalt Approach • Closure – Tendency to fill in gaps in figures see incomplete figures as complete. and

Subliminal Messages • Brief auditory or visual messages that are presented below the absolute threshold.

Depth Perception • BINOCULAR CUES – visual cues that depend on the action of both eyes. • MONOCULAR CUES – visual cues that are just as effective with one eye as with both.

Depth Perception • Visual Cliff Experiment • Develops around 6 months of age video clip

Monocular Depth Cues - Relative height - Texture-density gradient - Interposition - Motion parallax - Light and shadow - Linear perspective - Relative motion

Relative Height • Objects that appear further away from another object are higher on your plane of view.

Interposition • The overlapping of images; the object we can see in it’s entirety is closer than one whose outline is interrupted by another object.

Light & Shadow • Brightly lit objects appear closer • Objects in shadows appear farther away

Texture-Density Gradient • The farther away an object is, the less detail we can identify.

Motion Parallax • The apparent movement of stationary objects relative to one another that occurs when the observer changes position.

Linear Perspective • When parallel lines converge with increasing distance (such as roads, railway lines, electric wires, etc).

Relative Motion • Objects close to you appear to be moving in the opposite direction. • Objects far away from you appear to be moving in the same direction.

Binocular Depth Cues • CONVERGENCE – the degree to which the eyes turn in to focus on a close object.

Binocular Depth Cues • RETINAL DISPARITY – the difference in the apparent position of an object as seen by the left and right retinas.

Perceptual Constancy • CONSTANCY – the tendency to perceive certain objects in the same way regardless of changing angle, distance, or lighting. – Size – Shape – Color

A. B. Can you trust your eyes?

Illusions • Perceptions that misrepresent physical stimuli. Muller-Lyer Illusion

ESP • An ability to gain information by some means other than the ordinary senses. 1. Clairvoyance 2. Telepathy 3. Psychokinesis 4. Precognition

1. Clairvoyance ESP -perceiving objects or info without sensory input. 2. Telepathy -reading someone’s mind or transferring one's thoughts. 3. Psychokinesis -moving objects with your mind. 4. Precognition -ability to foretell events.