Chapter 4: Sense and Perception

Notes

Sensation & Perception

• Sensation:

  • Stimulation of the sense organs.

• Perception:

  • The selection, organization, and interpretation of sensory input

• Psychophysics:

  • The study of how physical stimuli are translated into psychological experiences.

  • Gustav Fechner (1860):

    • Authored Elemente der Psychophysik.

• Gestalt Psychology

  • Emphasizes organizing visual elements into whole forms. - Principles: Figure-ground relationship, similarity, proximity, closure, and continuity

• Illusions and Perceptual Constancies

  • Context can create illusions in perception (e.g., size constancy disruptions).

  • Examples include visual illusions like the Müller-Lyer illusion.

• The perception process involves complex interactions between sensory inputs, contextual factors, and cognitive processes.

• Stimulus:

  • Any detectable input from the environment.

Thresholds

• Absolute Threshold:

  • For a specific type of sensory input, the minimum amount of stimulation that an organism can detect.

  • Defined as the intensity detected 50% of the time.

Examples of Absolute Thresholds:

• JND:

  • The smallest difference in stimulation that a specific sense can detect.

  • Also known as Difference Threshold.

• Weber’s Law:

  • The size of a JND is constant and proportional to the size of the original stimulus.

  • Constants differ based on sensory input types.

• Measurement in perception is relative, not absolute.

• Fechner’s Law:

  • Subjective sensation is proportional to the logarithm of stimulus intensity.

  • As stimulus intensity increases, perceived increases are smaller.

• Signal Detection Theory:

  • Suggests detection of stimuli involves both decision and sensory processes influenced by various factors beyond stimulus intensity.

• Signal Detection Outcomes:

  • Present Stimulus:

    • Hit: Correctly detecting stimulus.

    • Miss: Failing to detect stimulus.

  • Absent Stimulus:

    • False Alarm: Incorrectly reporting stimulus is present.

    • Correct Rejection: Correctly identifying absence of stimulus

• Subliminal Perception:

  • Registration of sensory input without conscious awareness.

  • Notably studied starting with James Vicary in 1957.

• Sensory Adaptation:

  • Gradual decline in sensitivity due to prolonged stimulation.

  • An adaptive process that helps in detecting changes in the environment.

The Auditory System and Sound Waves

• Sense of Hearing

• Sound Waves:

  • Vibrations of molecules traveling through a medium (e.g., air).

  • Travel at a fraction of the speed of light.

Characteristics of Sound Waves

• Amplitude:

  • Affects perception of loudness.

• Frequency:

  • Measured in Hertz (Hz); affects pitch.

• Wavelength:

  • Relates to distance and pitch.

• Purity:

  • Influences timbre.

• Hearing Capacities

  • Humans: 20 Hz to 20,000 Hz

  • Dogs: 50 Hz to 45,000 Hz

  • Cats: 45 Hz to 85,000 Hz

  • Bats: 20 Hz to 120,000 Hz

  • Dolphins: 0.25 Hz to 200,000 Hz

  • Elephants: 5 Hz to 10,000 Hz

• The Human Ear

  • Three Major Parts:

    • Outer ear, middle ear, and inner ear.

  • Functions:

    • Conducts sound waves and converts vibrations into neural activity.

• Anatomy of the Ear

  • Outer Ear: Pinna (ear flap) and ear canal.

  • Middle Ear: Ossicles (malleus, incus, stapes) and the tympanic membrane (eardrum).

  • Inner Ear: Cochlea (transforms vibrations) and semicircular canals (balance).

• Theories of Hearing

  • Pitch Perception:

    • Two main theories:

      1. Place Theory:

         • Pitch corresponds to vibrations along the basilar membrane.

      2. Frequency Theory:

         • Pitch corresponds to the overall vibration frequency of the basilar membrane.

• Auditory Localization

  • Locating Sound:

    • Ears set apart help in sound localization.

    • Two important cues:

      • Sound Intensity: Loudness differences between ears.

      • Timing of Sounds: Arrival timing differences aid in localization.

• Inability to Hear

  • 1 in 1000 people is deaf; many others have hearing deficits.

  • Types of Deafness:

    • Conductive Deafness: Involves outer/middle ear.

    • Nerve Deafness: Involves the inner ear.

  • Noise-induced hearing loss is common.

• Effects of Music

  • Musicians often have larger motor, auditory, and visuospatial areas in the cerebellum.

  • Music training is linked to language abilities and cognitive enhancements (e.g., Mozart Effect).

Other Sensory Systems

The Gustatory System

• Sense of Taste:

  • Stimuli are soluble chemical substances with receptors located in taste buds.

  • Tastes and Taste Buds

  • Taste perception varies based on neural activity in receptors, some preferences innate, others learned.

  • Variability in taste sensitivity: non-tasters, medium tasters, supertasters.

  • Four primary tastes: salty, sweet, sour, bitter (Umami as fifth).

  • Taste Bud Types:

    • Fungiform, Circumvallate, Foliate papillae.

• Perception of flavour:

  • Flavour is influenced by taste, smell, and tactile sensations.

  • Odour perception is vital for flavour interpretation

The Olfactory System

• Sense of Smell:

  • Humans have about 350 types of olfactory receptors, distinguishing around 10,000 odours

• Pheromones: Chemical signals influencing behaviors between individuals of the same species.

The Tactile System

• Sense of Touch:

  • Physical stimuli are mechanical, thermal, and chemical energies.

• Perception includes warmth, cold, pressure, and pain.

• Tactile Receptors: Human skin has at least six types of sensory receptors, allowing for accurate localization of touch.

• Perceiving Pain: Pain perception can be influenced by various factors, including expectations and coping mechanisms (e.g., placebo effect)

• Gate Control Theory:

  • Incoming pain sensations pass through a 'gate' in the spinal cord, influenced by activity patterns.

The Kinesthetic & Vestibular Systems

• Kinesthetic System: Monitors body positions.

• Vestibular System: Responds to gravity, critical for orientation and balance

The Visual System

Sense of Sight:

• Light is the primary stimulus, traveling as a wave.

• Light Properties

• Amplitude: Affects brightness perception.

• Wavelength: Affects color perception.

• Purity: Influences saturation of colors.

Anatomy of the Eye

• Major Components: Iris, cornea, pupil, lens, retina.

• Functions: Channeling light to retina where images are processed.

• Visual Receptors:

  • Cones: Responsible for Daytime and color vision (concentrated in fovea)

  • Rods: Important for night and peripheral vision.

• Adaptation and Colour

  • Dark Adaptation: Process where eyes become more sensitive in low light; takes ~30 minutes.

• Colour Perception

  • Properties of Light: Influence the perception of hue, brightness, and saturation.

  • Colour Mixing: Two types: Additive and subtractive.

• Theories of Colour Vision

  • Trichromatic Theory: Three types of receptors for red, green, and blue influences color perception and explains color blindness.

  • Opponent-Process Theory: Color perception involves three pairs of opposing colors.

• Depth Perception

  • Definition: Interpretation of visual cues for spatial understanding.

  • Cues for Depth Perception:

    • Monocular Cues: Based on single eye views. - Examples include linear perspective and relative size.

    • Binocular Cues: Based on differing views from two eyes, involving retinal disparity and convergence.

• Cognition and Vision

  • Bottom-up Processing: Recognizing object by starting with individual elements.

  • Top-down Processing: Recognition influenced by existing knowledge and expectations.

Reading

Psychology Can. 6th Ed. Schacter Chapter 4