Pcych 1010 Sensation

Sensation

Psychophysics

• Psychophysics is the study of the relationship between physical stimuli and the sensations and perceptions they produce.

Transduction

• Transduction refers to the process by which sensory receptors convert physical energy (i.e., light, sound, chemical) into neural signals that can be processed by the brain.

Sensory Receptors

• Specialized cells that detect specific types of stimuli (e.g., photoreceptors in the eyes for light).

Sensory Adaptation

• The decrease in sensitivity to a constant stimulus over time. For example, if you enter a dark room, you initially notice the darkness but gradually adapt to it as your vision adjusts.

Absolute Threshold

• The minimum intensity of a stimulus that can be detected 50% of the time.

Just Noticeable Difference (JND)

• The smallest change in a stimulus that can be detected.

Weber’s Law

• A principle stating that the just noticeable difference for a stimulus is proportional to the magnitude of the original stimulus. This can be represented as: $ext{JND} = k imes I$ where

  • JND = Just Noticeable Difference

  • k = a constant

  • I = initial stimulus intensity

Attention

Selective Attention

• The process of focusing on a specific object in the presence of other distracting stimuli.

Inattentional Blindness

• A failure to notice a fully visible but unexpected object because attention was engaged on another task.

Change Blindness

• A perceptual phenomenon that occurs when a change in a visual stimulus goes unnoticed by the observer.

Binding

• The process by which the brain integrates sensory information from different modalities (e.g., sight, sound, touch) to produce a unified perception.

Vision

Structures

• The primary structures involved in vision include the eyes, optic nerves, and visual cortex in the brain.

Trichromatic Theory

• This theory posits that color perception is based on the activity of three types of cone photoreceptors, which are sensitive to different wavelengths of light (red, green, blue).

Opponent Process Theory

• This theory suggests that color perception occurs in opposing pairs (e.g., red-green, blue-yellow), where activation of one color inhibits the perception of the other.

Audition

Structures

• The major structures involved in hearing include the outer ear, middle ear, inner ear, and auditory cortex.

Place Theory

• A theory that states different frequencies of sound are perceived based on where they stimulate the basilar membrane within the cochlea.

Frequency Theory

• A theory positing that the frequency of auditory nerve impulses matches the frequency of a sound wave, determining pitch perception.

Olfaction

• The sense of smell; it involves chemical detection by olfactory receptors in the nasal cavity.

Gustation

• The sense of taste; it involves the perception of flavors through taste buds on the tongue.

Somatosensory

• Refers to the sensory processes related to touch and body position, which includes:

Proprioceptive

• The sense of body position and movement, giving an internal sense of the body's position in space.

Vestibular

• The sense that contributes to balance and spatial orientation, which is provided by the inner ear's semicircular canals.

Perception

Processing

Bottom-Up Processing

• An approach to perception that begins with the input of sensory data, constructing perception from the details upward.

Top-Down Processing

• An approach that begins with the observer’s prior knowledge, expectations, and experiences affecting interpretation of sensory stimuli.

Parallel Processing

• The ability of the brain to simultaneously process multiple aspects of a sensory experience (e.g., color, motion, depth).

Perceptual Hypotheses

• The predictions or expectations about what we will perceive, influencing our interpretation of sensory information.

Perceptual Sets

• A mental predisposition to perceive things in a certain way, influenced by experiences, expectations, and context.

Perceptual Constancy

• The tendency to perceive objects as unchanging despite changes in sensory input. Types include:

Size Constancy

• The perception that an object retains a constant size, regardless of distance changes.

Shape Constancy

• The perception that an object's shape remains constant even when the angle of view changes.

Color Constancy

• The perception that an object’s color stays the same under varying illumination conditions.

Gestalt Principles

• These are principles that describe how we organize visual information into meaningful wholes. They include:

Proximity

• Objects that are close together are perceived as belonging to the same group.

Similarity

• Objects that are similar in appearance are grouped together.

Continuity

• Lines and patterns are perceived as continuing in a direction rather than being broken.

Closure

• The tendency to perceive incomplete figures as complete.

Symmetry

• Symmetrical images are perceived as part of a whole.

Figure-Ground

• The ability to distinguish an object from its background.

Faces

• The tendency to recognize faces as distinct objects, given their importance in human interaction.

Motion

• The perception of motion involves changes in position over time, impacted by factors such as speed and direction.

Depth Perception

• The ability to perceive the world in three dimensions, crucial for judging distance; includes:

Monocular Cues

• Cues for depth perception that can be perceived with one eye, including:

Relative Size

• Smaller objects are perceived as more distant.

Occlusion

• If an object overlaps another, it is perceived as closer.

Linear Perspective

• Parallel lines appearing to converge in the distance indicate depth.

Height in Plane

• Objects higher in the visual field are perceived as farther away.

Light & Shadow

• Shadows and highlights provide depth cues based on their intensity and placement.

Binocular Cues

• Cues requiring both eyes for depth perception, including:

Disparity

• The slightly different views of an object from each eye provide depth information.

Convergence

• The inward angle of the eyes when focusing on a nearby object provides depth information.

Perceptual Errors

• Mistakes in perception that can occur due to sensory adaptation, attentional focus, or other biases. These errors illustrate the complexities of sensory processing and the influence of contextual factors on how we perceive our environment.