Sensation and Perception Quiz

Sensation and Perception

• Sensation is the activation of the sense organs by a physical stimulus.
• Perception is the sorting, interpretation, analysis, and integration of stimuli by the sense organs and brain.
• A stimulus is any energy that produces a response in a sense organ.

Psychophysics

• Psychophysics is the study of the relationship between the physical aspects of a stimulus, and our psychological experience of it.
• Humans have more sensory abilities than just sight, sound, taste, smell, and touch. For example, touch includes pain, pressure, temperature, and vibration.

Absolute Thresholds

• Absolute threshold is the lowest intensity of a stimulus that can be detected 50% of the time.
• Noise (background stimulation) can interfere with the perception of other stimuli. This affects all senses, not just auditory.
• As the strength of a stimulus increases, the likelihood of detection increases gradually.
• Our senses are highly sensitive. Increased sensitivity could lead to distractions. (e.g., hearing air molecules hitting the eardrum). Ideal vs. real conditions make detection harder (e.g., noise).

Difference Thresholds

• Difference threshold is the smallest level of change in a stimulus needed to perceive a difference. Also known as the just noticeable difference (JND).
• The size of the change needed depends on the initial intensity of the stimulus.

Weber's Law

• Weber's Law states that the just noticeable difference (JND) is a constant proportion of the initial stimulus intensity, rather than a constant amount.

Sensory Adaptation

• Sensory adaptation is an adjustment in sensory capacity after prolonged exposure to unchanging stimuli.
• Sensory receptors are most responsive to changes in stimulation, not constant stimulation.
• Constant stimulation does not produce a sustained reaction.
• Repeated exposure to strong stimuli decreases sensitivity of sensory receptors.
• Adaptation allows the brain to mentally “turn down the volume” of constant stimuli.

Contextual Influences

• Contextual influence suggests our judgments of stimuli are affected by their context.
• For example, a small envelope with the same weight as a large one can be perceived as heavier due to context.

Vision

• Vision begins with light, which is electromagnetic radiation measured in wavelengths.
• The human eye can detect a range of wavelengths, the visual spectrum, including colors of the rainbow (violet to red).
• Cornea: Transparent, protective outer layer refracting light.
• Iris & Pupil: Coloured part and opening, controlling the amount of light entering the eye.
• Lens: Focuses light onto the retina by changing its thickness.
• Retina: Contains receptor cells (rods & cones): rods are for peripheral and night vision; cones are for sharp focus, color perception, and bright light vision. Cones are concentrated in the fovea (a sensitive area of the retina).
• Dark adaptation takes longer for rods than cones (20-30 minutes for rods vs. a few minutes for cones.)

Color Vision

• Normal color vision can distinguish at least 7 million colors.
• Color blindness occurs when certain types of cones are missing or function poorly (e.g., deuteranopia, protanopia, tritanopia).
• Trichromatic theory suggests three types of cones responsive to different wavelengths of light (blue-violet, green, and yellow-red).
• Opponent-process theory proposes four types of receptors processing colors in pairs (blue-yellow, red-green, and black-white).

Hearing (Mod. 10)

• The ear has outer, middle, and inner sections.
• Outer ear: Functions as a reverse megaphone, funneling sound waves to the eardrum.
• Middle ear: Contains the eardrum (vibrating membrane) and bones (hammer, anvil, stirrup) that amplify sound waves and transfer them to the inner ear.
• Inner ear: The cochlea, a fluid-filled structure, converts sound vibrations into neural signals for the brain. These signals are transmitted via hair cells along the basilar membrane.
• Theories of hearing include place theory and frequency theory, which describe how different areas of the basilar membrane are activated by different frequencies of sounds, and how the entire basilar membrane vibrates in response to sound. Different frequencies activate different areas and in different ways along the basilar membrane.

Other Senses

• The skin senses touch, pressure, temperature, and pain.
• Pain is an important sense for survival, highlighting the importance of body cues responding to the environment.
• Many psychological and cultural factors impact sensitivity and experience of pain.
• Smell involves olfactory cells responding to molecules of substances in the nasal passages.
• Taste involves receptor cells responding to basic qualities (sweet, sour, salty, bitter, and umami).

Perceptual Organization (Mod. 11)

• Perception is a constructive process, going beyond the stimuli to construct a meaningful situation.
• Gestalt laws of organization describe how we organize bits of information into meaningful wholes, including the concepts of closure, proximity, similarity, and simplicity.
• Top-down processing relies on higher-level knowledge (experience, expectations, motivations) to guide/influence perception.
• Bottom-up processing starts with individual stimulus components and builds to the whole (e.g., recognizing shapes to form a letter).

Depth Perception

• Depth perception involves our ability to see the world in three dimensions and perceive distance.
• Binocular cues (using both eyes) and monocular cues (using one eye) are involved in depth perception.
• Binocular disparity: Difference in images seen by the left and right eyes helps the brain estimate an object's distance.
• Monocular cues, such as relative size, texture gradient, linear perspective, motion parallax, and covergence, provide information about depth.

Illusion & Subliminal

• Perceptual illusions highlight how senses can produce errors in perception.
• Subliminal perception refers to stimuli we perceive unconsciously (below conscious awareness). Some studies show it can subtly influence impressions but lacks reliable scientific support for consistently altering behavior.