April 8, 2014 

Sensation and Perceptions

• Sensation: Your window to the world
• The process by which our sensory receptors and nervous system receive stimulus from the environment
• Perception: Interpreting what comes in your window

Bottom-Up v. Top-Down Processing

• Bottom-Up- Begins within the sense receptors and works up to the brain's integration of sensory information (Thalamus)
• Top-Down Processing- Information processing guided by higher level mental processes

Absolute Threshold

• The minimum stimulation needed to detect a stimulus 50% of the time

Difference Threshold

• The minimum difference that a person can detect between two stimuli
• Also known as Just Notable Difference

Weber’s Law

• The idea that, to perceive a difference between two stimuli, they must differ by a constant percentage; not a constant amount

Signal Detection Theory

• Predicts how we detect a stimulus amid other stimuli
• Assumes that we do not have an absolute threshold

Sensory Adaptation

• Decreased responsiveness to stimuli due to constant stimulation

Selective Attention

• The focusing of conscious awareness on a particular stimulus

Transduction 

• Transforming signals into neural impulses 
• Information goes from the senses to the thalamus, then to the various brain areas in the brain 
• Conversion of one form of energy to another. 
• Ex: light energy to vision
• Chemical energy is smell and taste
• Sound waves to sound

Color Vision 

Young-Helmholtz Trichromatic (three color) Theory 

1. Three types of cones: 

• Red
• Blue
• Green
• These three types of comes can make millions of combinations of colors 
• Most color blind people simply lack cone receptor cells for one or more primary colors. 

Opponent - Process Theory

• The sensory receptors come in pairs 
• Red/Green 
• Yellow/Blue 
• Black/White
• If one is stimulated, the other is inhibited 

Hearing 

We hear sound waves 

• The height of the wave gives us the amplitude of the sound. 
• The frequency of the wave gives us the pitch of the sound. 

The Ear 

Transduction in the ear 

• Sound waves hit the eardrum then anvil then hammer then stirrup then oval window. 
• Everything is just vibrating. 
• Then the cochlea vibrates.
• The cochlea is lined with mucus called basilar membrane. 
• In basilar membrane there are hair cells.
• When hair cells vibrate they turn vibrations into neural impulses which are called Organ of Corti.
• Sent then to thalamus up auditory nerve.

Place Theory 

• Different hairs vibrate in the cochlea when there are different pitches. 
• So some hairs vibrate when they hear high pitches and other vibrate when they hear low pitches. 

Frequency Theory 

• All the hairs vibrate but at different speeds. 

Deafness 

Conduction Deafness 

• Something goes wrong with the sound and the vibration in the say to the cochlea. 
• You can replace the bones or get a hearing aid to help. 

Nerve (sensorineural) Deafness 

• The hair cells in the cochlea get damaged 
• Loud noises can cause this type of deafness 
• NO WAY to replace the hairs 
• Cochlea implant is possible.   

Smell & Taste 

• Sensory Interaction: the principle that one sense may influence together. 

Taste 

• We have bumps in our tongue called papillae. 
• Taste buds are located on the papillae (they are actually all over the mouth).
• Sweet, salty, sour and bitter. 

Umami - flavorful, savory taste. 

Touch 

• Receptors located in our skin. 
• Gate control Theory of Pain - This is where the spinal cord contains a neurological gate that blocks pain signals or allows them to pass onto the brain. 

Vestibular Sense 

• Tells us where our body is oriented in space. 
• Our sense of balance. 

Kinesthetic Sense 

• Tells us where our body parts are. 
• Receptors located in out muscles and joints. 

Perception 

• The process of organizing and interpreting information. Enabling us to recognize meaningful project and events. 

Gestalt Philosophy 

• The whole is greater than sum of the parts. 

Figure-Ground Relationship 

• The organization of the visual field into objects (figures) that stand out from their surroundings (ground).

Grouping 

• The perceptual tendency to organize stimuli into groups that we understand. 

Depth Perception 

• The ability to see objects in three dimensions although the images that strike the retina are two dimensional. 
• Allows us to judge distance. 

Binocular Cues 

• Brings out the concept of Retinal Disparity: a binocular cue for seeing depth. 
• The closer an object comes to you the greater the disparity is between the two images.