Sensation and Perception: How We Experience the World

• Sensation and perception involve receiving sensory information, processing it in the nervous system, and consciously experiencing the world.

Sensation versus Perception

• Sensation happens when sensory receptors detect sensory stimuli.
• Sensory receptors are specialized neurons responding to particular stimuli.
• Perception involves the organization, interpretation, and conscious experience of sensations.
• Perception is how sensory information is interpreted and affects interaction with the world.
• Perception involves both bottom-up processing (sensory information driven) and top-down processing (knowledge and expectancy driven).
• Absolute threshold is the minimum stimulus energy needed for detection 50% of the time.
• Just noticeable difference (jnd), or difference threshold, is the ability to detect differences between stimuli.
• Sensory adaptation is not perceiving constant stimuli over time.
• Attention determines what is sensed versus perceived.
• Inattentional blindness is failing to notice something fully visible due to active attention elsewhere.
• Motivation affects perception; signal detection theory explains how stimulus identification is affected by motivation within a distracting background.
• Perceptions are affected by beliefs, values, prejudices, culture, and life experiences.

Waves and Wavelengths

• Visual and auditory stimuli occur as waves with amplitude and wavelength.
• Amplitude is the distance from the centerline to the top or bottom of a wave.
• Wavelength is the length of a wave from one peak to the next and is directly linked to frequency.
• Frequency is the number of waves passing a point in a given time.
• Light wavelength relates to color perception, while amplitude relates to brightness.
• Humans' visible spectrum ranges from 380 to 740 nm.
• Sound wave frequency relates to pitch perception, and amplitude relates to loudness.
• The audible range is between 20 and 20000 Hz.
• Loudness is measured in decibels (dB).
• Timbre is a sound’s purity and is affected by frequency, amplitude, and timing.

Vision

• The visual system constructs a mental representation of the world.
• Light waves pass through the cornea and enter the eye through the pupil.
• Light crosses the lens, focusing images on the fovea of the retina in normal vision.
• Cones function best in bright light, are sensitive to detail, offer spatial resolution, and enable color perception.
• Rods work well in low light, aiding vision in dim environments and peripheral movement perception.
• Retinal ganglion cell axons converge to form the optic nerve, exiting the eye.
• The optic chiasm is an X-shaped structure below the cerebral cortex where optic nerves merge.
• The trichromatic theory of color vision says that all colors are made by combining red, green, and blue.
• The opponent-process theory of color vision states that color is coded in opponent pairs: black-white, yellow-blue, and green-red.
• Monocular cues need one eye; binocular cues need both eyes.
• Binocular disparity is the slightly different view each eye receives.
• Linear perspective is a monocular cue where converging parallel lines indicate depth.

Hearing

• The auditory system converts pressure waves into meaningful sounds.
• The outer ear includes the pinna, auditory canal, and tympanic membrane (eardrum).
• The middle ear contains ossicles: malleus (hammer), incus (anvil), and stapes (stirrup).O
• The inner ear contains semi-circular canals and the cochlea.
• The basilar membrane, within the cochlea, holds hair cells.
• Hair cells are the auditory receptor cells.
• The temporal theory of pitch perception states that frequency is coded by a sensory neuron’s activity level.
• The place theory of pitch perception states that different parts of the basilar membrane are sensitive to different frequencies.
• Monaural (one-eared) and binaural (two-eared) cues are used to localize sound
• Interaural level difference is when a sound from one side is more intense at the closer ear.
• Interaural timing difference is the small difference in arrival time at each ear.
• Conductive hearing loss is due to problems delivering sound to the cochlea.
• Sensorineural hearing loss is caused by aging, trauma, infections, diseases, medications, noise exposure, tumors, and toxins.

The Other Senses

• Taste (gustation) and smell (olfaction) are chemical senses using receptors that respond to molecules.
• Taste buds are groupings of taste receptor cells with hair-like extensions.
• Olfactory receptor cells are in a mucous membrane at the top of the nose.
• Information from the olfactory bulb goes to the limbic system and olfactory cortex.
• Pheromones are chemical messages sent by individuals.
• Meissner’s corpuscles, Pacinian corpuscles, Merkel’s disks, and Ruffini corpuscles are touch receptors throughout the skin.
• Thermoception is temperature perception, and nociception indicates potential harm/pain.
• The vestibular sense helps maintain balance and posture.
• Proprioception is body position perception, and kinesthesia is perception of body movement.

Gestalt Principles of Perception

• Gestalt psychology says the whole is different from the sum of its parts.
• The figure-ground relationship segments our visual world into figure and ground.
• Proximity groups things close together.
• Similarity groups similar things together.
• The law of continuity perceives continuous, smooth lines rather than jagged, broken lines.
• The principle of closure organizes perceptions into complete objects, not parts.
• Pattern perception is the ability to identify figures and shapes.

Explore the difference between sensation and perception. Learn about sensory receptors, absolute thresholds, and how we interpret sensory information. Understand the roles of attention, bottom-up and top-down processing in shaping our conscious experience.