Motion Perception and Sensitivity

Motion Perception

• Motion perception declines with age but can be trained.
• Motion captures attention, aiding object identification.
• Motion helps distinguish objects from the background and reveals their form.
• Difficulty perceiving motion can lead to problems like pouring liquids, understanding emotional cues in conversations, and increased risk of accidents.

Sensitivity to Motion

• Detecting a moving object is easier if it's smaller.
• Intelligent individuals tend to suppress irrelevant background information while focusing on important stimuli with large movements.
• Context affects how easily motion is detected. Homogenous backgrounds make small movements harder to see. Patterned backgrounds (like vertical stripes) make horizontally moving objects easier to see than in a homogenous context.

Real vs. Apparent Motion

• Gestalt principle: The whole is greater than the sum of its parts. Apparent motion: elements moving is perceived as the whole moving in a circular path, while individual elements move in a straight line.
• Persistence of vision: Successive images appear as a single moving object.

Perceiving Biological Motion

• Identifying the motion of living things from a large distance.
• Perceiving biological movement happens quickly due to the dorsal pathways in the brain, allowing rapid identification compared to other visual processing.

Depth and Size Perception

• Depth cues are signals that indicate depth in an object or scene.
• Accommodation of the lens: Fine motor muscles adjust lens shape to focus on near or far objects.
• Convergence of the eyes: Muscles align eyes to point at a single object; only works up close.
• Pictorial cues: occlusion, relative height, relative size, perspective convergence, texture gradient, shadows, are cues of depth that can be represented in two-dimensional pictures.
• Binocular retinal disparity: Differences in the images each eye receives that creates a perception of 3D space. It is effective up to 10 meters.
• Atmospheric perspective: Objects further away appear fainter or bluer.
• Familiar size: Using prior knowledge of an object's typical size to judge distance.

Perceiving Size From Vision

• Visual angle: The angle an object subtends at the eye. A bigger angle indicates a larger object or one that is closer.
• Distance: The further an object, the smaller its visual angle.
• Size constancy: An object's perceived size remains stable despite changes in its distance perceived distance from the observer.
• Size-distance scaling: The brain perceives size by considering both retinal size and perceived distance.

Auditory Perception

• Sound is perceived as pressure changes in air or water (compressions and rarefactions) that cause the waves.
• Pitch is related to frequency, the number of cycles per second (Hz), which also determines loudness (intensity).
• Timbre is the quality of a sound, which depends on the harmonics present. Different instruments can have the same pitch and loudness, but different timbres.
• Auditory localization: Ability to determine the location of a sound source in space. Interaural level differences (ILD) and interaural time differences (ITD) are cues used by the brain for perceiving sound location.

Auditory Areas in the Cortex

• Auditory cortex receives sounds, which are processed for 'what' and 'where'.
• Music training can increase the size of the auditory cortex.

Hearing Loss

• Conductive hearing loss: affects the outer or middle ear.
• Sensorineural hearing loss: affects the inner ear or auditory nerve.
• Mixed hearing loss: combination of both.

Auditory Masking

• The auditory system can filter out unwanted sounds, a process also known as masking.
• Sounds present in the surrounding environment can be masked by others (e.g., sounds from two close sources may sound like a single sound).