Lecture 4- Sensation, Perception, and Attention

• Topic 4 is titled sensation and perception

Prosopagnosia

• Sensing and perceiving are connected
• Involves a cognitive disorder of face perception
• Causes difficulty perceiving or recognizing faces
• Is a form of face blindness, but with intact vision

Sensation and Perception

• Sensation is the detection of physical energy by the sense organs
• Perception is the brain's interpretation of raw sensory data
• Includes sight (visual), smell (olfactory), hearing (auditory), taste (gustatory), touch (tactile), balance and movement (vestibular), and body awareness (proprioception)

Transduction

• Transduction is the conversion of one energy form into another
• Sensory information is received via sensory receptor cells
• Stimulation is transformed into neural impulses (action potentials)
• Which delivers neural information to the brain

Multitasking Brain

• Bottom-up processing forms perception based on building simple input into more complex perceptions
• Top-down processing is a perceptual process in which memory and other cognitive processes are needed to interpret incoming sensory information

Sensory Adaptation

• Activation is highest at first detection
• Sensory adaptation occurs when sensory receptor cells become less responsive to a stimulus that is unchanging
• Becoming less noticeable and serving to conserve energy and focus on novelty and changes

Psychophysics

• Psychophysics measures sensation
• Sensation begins with a detectable stimulus
• Absolute threshold is the minimum intensity of a stimulus a person can detect half the time
• Example thresholds include seeing a candle 48 km away on a clear night or tasting 1 tbsp of sugar in 7.5 L of water

Subliminal Perception

• Subliminal perception involves perceiving stimuli presented below the absolute threshold
• Perception is not equal to persuasion, there is little practical application through subliminal perception

Just Noticeable Difference (JND)/Difference Threshold

• The degree of difference must exist between two stimuli before the difference is detected
• Many decisions rely on ability to detect small differences
• Weber's law states JND between 2 stimuli is not an absolute amount, but relative to the intensity of the first stimulus
• The more intense the initial stimulus, the larger the difference needs to be to be noticed

JND and Marketing

• Marketers are concerned that positive changes are discernible (at or just above JND)
• Negative changes are not discernible (below JND)
• Changes are subtle enough to keep current customers

Role of Attention

• Selective attention focuses on a specific aspect of sensory input while ignoring other stimuli in the environment
• Attention is considered a bottleneck
• Other channels are processed at some level
• Inattentional blindness causes failure to detect an unexpected stimulus in plain sight
• This happens because of limited attentional resources, so focus falls on deeming what is important
• Change blindness means failure to detect changes in enviroment
• Limited resources impact age or distraction

Officer Example

• Boston officer charged with misconduct for lying, claimed he did not see officers beating a suspect as he ran past while chasing a murder suspect
• Simulation study showed 65% missed the fight at night and 44% missed the fight during broad daylight

Senses

• Include sight (visual), smell (olfactory), hearing (auditory), taste (gustatory), touch (tactile), balance & movement (vestibular) and body awareness (proprioception)

Vision

• Vision starts with light

Transduction

• Photoreceptors are needed for rods and cones

The Eye

• Iris is the muscle ring controlling pupil size
• Iris controls amount of light entering eye (via the pupil)
• Light enters through the cornea
• Lens focuses light rays into image on eyeball's retina
• The retina is the light-sensitive back inner surface of eye - nerve cells here!
• The retina contains rods and cones
• Optic nerve carries neural impulses from eye to brain
• Blind spot exists where optic nerve leaves the eye

Main Job of Iris

• Controlling light that enters the eye
• It adjusts to imaginary light
• Iris constricts with disgust or when you're about to say "NO"
• It dilates with romance or trust (autonomic arousal)

Additional Facts

• Scan the QR code to find the blind spot
• Rotate phone/tablet horizontally

Retinal Receptors

• Rods detect black, white, and gray and are sensitive to movement
• Peripheral & twilight vision happens due to low light situations
• Cones provide sharp focus, colour perception, and detail
• Cones work well in daylight and cluster around fovea

Colour Vision

• There are different theories of colour perception
• The trichromatic theory is where the retina contains red, green & blue receptors and when stimulated, these receptors can produce perception of any colour
• Consistent with three types of cones in eyes
• Explains colour blindness but not afterimages
• In the opponent process theory colours are perceived in terms of three pairs of opponent colours: red or green, blue or yellow, and black or white
• Colour processing combines the trichromatic theory and opponent processing theory

Colour Processing Stages

• The retina's red, green, and blue cones respond in varying degrees to different colour stimuli
• The cones' responses are processed by opponent-process cells

When Sight is Lacking

• Blindness can result in reorganization of other sensory cortices and changes in other senses (i.e., compensation)
• Echolocation might improve following blindness
• Visual agnosia includes object recognition deficit and damage to higher visual cortical areas
• Blindsight indicates above-chance visual performance of cortically blind individuals with damage to area VI

Perceptual Organization

• Perception a constructive process
• Requires people to go beyond the stimuli presented to construct a meaningful situation
• We dont passively respond to visual stimuli, but actively try to organize and make sense of what we see

Gestalt Principles

• Govern how information is organized into meaningful wholes
• States the whole is more than the sum of its parts
• Born with built in tendencies to organize incoming sensory info

Perceptual Constancy

• Is the recognition that objects are constant and unchanging even though sensory input about them is changing

Colour Constancy

• Is the ability to perceive an object as having relatively the same colour under varying illumination conditions

Depth Perception

• Monocular depth cues rely on one eye
• Relative size, texture gradient, overlap/occlusion, height in field of view, linear perspective and motion parallax
• Binocular depth cues require both eyes and include convergence and disparity

Hearing (Audition)

• Sound is movement of air molecules brought about by vibration of an object
  • Frequency = pitch (Hz)
  • Amplitude = loudness (dB)

Sound Frequencies

• Defined by pitch (Hz)
• Defined by amplitude (dB)

Hearing Loss and Damage

• Decibel levels can lead to damage over time

Sensing Sound

• Outer ear collects sound
• Middle ear acts as mechanical amplifier
• Inner ear transduces vibrations into neural message

Additional Facts

• Infant hearing programs test babies' hearing

When Hearing is Lacking

• Result of malfunction of the ear especially a failure of eardrum or ossicles
• Nerve deafness occurs due to damage to auditory nerve
• Nerve-induced hearing loss happens because of damage hair cells due to repeated loud noises
• Sudden Sensorineural hearing loss

The Multitasking Brain Explained

• Bottom-up processing begins with sensory receptors and senses basic features of stimuli and integrates them
• Top-down processing is guided by higher-level mental processes
• Previous experience, expectations are used to interpret what senses detect
• Perception is built from senses, and influenced by experiences, biases, and culture

Other Influences

• Perceptual sets include predisposition or readiness to perceive something in a particular way (top-down influence)
• Influenced by experiences, expectations, and emotions
• Context effects on perception recall perception in different contexts
• Context helps form perception and interpretation of a situation
• Cultural context affects what perceive

Emotions

• Emotions sway perceptions
• Sad music predisposes people to perceive sad meanings
• Anger increases likelihood neutral items will be mistaken as weapons
• Worrying about panic leads to interpreting physical sensations as panic

Cross Talk Between Senses

• This is where stimulation of one sense evokes another
• McGurk effect and rubber hand illusion
• Sounds with colour, colours with taste