Ch. 4 Sensation

Sensation

The process of detecting external stimuli through sensory organs and converting it into neural signals.

Perception

The process by which the brain organizes, interprets, and gives meaning to sensory information.

Transduction

The conversion of sensory stimuli (like light, sound) into electrical neural impulses sent to the brain.

Absolute Threshold

The minimum amount of stimulation needed to detect a stimulus 50% of the time.

Difference Threshold (Just Noticeable Difference)

The smallest difference between two stimuli that can be detected 50% of the time.

Weber’s Law

The principle that the Just Noticeable Difference (JND) is a constant proportion of the original stimulus intensity, not a fixed amount.

Sensory Adaptation

A decrease in sensitivity to a constant level of stimulation over time.

Pathway of Light through the Eye

Cornea → Pupil → Lens → Retina.

Cornea

Bends light waves to help focus them.

Iris

Controls the size of the pupil.

Lens

Changes shape to focus light onto the retina (accommodation).

Retina

The light-sensitive inner surface of the eye containing photoreceptors (rods & cones).

Rods

Responsible for night vision, peripheral vision, detecting black and white.

Cones

Responsible for color vision and detailed vision, work best in bright light.

Optic Nerve

Carries neural signals from the retina to the brain’s visual cortex.

Blind Spot

The point where the optic nerve exits the eye; no photoreceptors are present there.

Main Parts of the Ear

Outer ear (pinna, ear canal), middle ear (ossicles: hammer, anvil, stirrup), inner ear (cochlea).

Cochlea

Contains fluid and hair cells that transduce sound waves into neural signals.

Auditory Nerve

Carries sound information from the cochlea to the brain.

Five Basic Tastes

Sweet, salty, sour, bitter, umami (savory).

Taste Receptors

Located in the taste buds on the tongue.

Olfactory Receptors

Detect smell in the nose.

Olfactory Bulb

Where smell signals are processed, linked to areas processing emotion and memory.

Somesthetic Senses

Touch, temperature, pain, pressure.

Vestibular Sense

The sense of balance and spatial orientation, located in the inner ear’s semicircular canals.

Kinesthetic Sense

Sense of body movement and position of limbs.

Top-Down Processing

Perception driven by prior knowledge, experiences, and expectations.

Bottom-Up Processing

Perception starting from raw sensory input, building up to a full perception.

Gestalt Principles

Psychological principles that describe how we organize visual information into wholes, like proximity, similarity, closure, continuity, and figure-ground.

Depth Perception

The ability to perceive the world in 3D and judge distance.

Perceptual Constancy

Recognizing that objects remain the same even when their appearance changes (like size, shape, color).