Intro to Sensation and Perception & Key Elements of Sensation

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Introduction to Sensation and Perception 

Sensation: how an organism receives (or detects) stimuli and information from the surrounding world via the sensory organs   
Perception: the interpretation of sensations 
  • Cognitive processes of receiving, encoding, storing and organizing sensations  

Absolute Threshold  
  • The weakest amount of a stimulus that a person can detect 50% of the time 
Bottom-up Processing: analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind

Top- down Processing: into processing guided by higher level mental processes as we construct perception, drawing on our experience and expectation

Signal Detection Theory

  • Predicts when an individual will decide if a stimulus is present or not based on both the signal's intensity and the individual's motivation. 
  • Based on the idea that an individual's absolute threshold is not constant and can impacted by attention, motivation, experience, and expectation
  • Researchers look to understand why people respond differently to the same stimuli. 
Subliminal Stimuli 
  • Stimuli below your absolute threshold. 
  • Priming: the activation, often unconsciously of certain association, thus predisposing one's perception, memory, or response. 
Difference Threshold
  • Just Noticeable Difference (JND)  
  • The smallest amount of chance between stimuli can be detected 
Weber's Law 
  • Based on the work of the psychophysicist Ernst Weber
  • A Formula for determining the JND 
  • The minimum amount of change needed to create a JND is constant percentage of the original stimulus 
  • Larger stimuli require greater increases in intensity for difference to be noticed   
  • Weber's constant for detecting difference in weight is .02
  • Works well for most senses for a wide range of intensities but does not work well for extremes 

Cocktail- Party Phenomenon

  • The cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations. 
  • Form of selective attention 

Key Elements of Sensation 


Sensory Adaptation 
Loss of sensitivity to stimuli when receptor cells are constantly stimulated  

Sensory Transduction
The transformation of energy from environment by specialized receptor cells in sensory organs into neural messages. 

Transduction in the senses 

Vision

  • Sense Organ: Eye 
  • Stimuli: light waves 
  • Specialized Receptor Cells: photoreceptor cells: rods and cones located in the retina 
  • Pathway to the brain: Optic Nerve < Thalamus< visual cortex in the occipital lobes 
Audition (Hearing) 
  • Sense Organ: Ear 
  • Stimuli: Sound Waves 
  • Specialized Receptor Cells: Cilia (hair cells) located on the basilar membrane of the cochlea
  • Pathway to the brain: Auditory Nerve< Thalamus< Auditory cortex in the temporal lobes  
Gustation (Taste) 
  • Sense Organ: Tongue 
  • Stimuli: Molecules dissolved in saliva on the tongue 
  • Specialized Receptor cells: Taste receptor cells in the taste buds located in the papillae 
  • Pathway to the brain: Cranial Nerve<Thalamus<Cortex at the junction of the temporal and parietal lobes 
Olfaction (Smell) 
  • Sense Organ: Nose 
  • Stimuli: Molecules dissolved in the mucous membranes of the nose 
  • Specialized Receptor Cells: Olfactory  receptor cells that communicate to the olfactory bulb 
  • Pathway to the brain: Olfactory Bulb< Temporal lobes< Limbic system 
Somatic (Touch) 
  • Sense Organ: Skin 
  • Stimuli: Pressure in skin based on intensity of stimuli 
  • Specialized Receptor Cells: Pressure receptor located in the skin 
  • Pathway to the brain: Cranial or spinal nerves< Thalamus< Somatosensory cortex at the front of the parietal lobes  
Temperature
  • Sense Organ: Skin 
  • Stimuli: Temperature changes in stimuli 
  • Specialized Receptor Cells: Warm and cold receptor cells located in the skin 
  • Pathway to the brain: Spinal Nerves< Thalamus< Somatosensory cortex at the front of the parietal lobes (temperature can interact with touch sensations 
Pain
  • Sense Organ: Skin 
  • Stimuli: Tissue injury or damage 
  • Specialized Receptor Cells: Pain receptors located in the skin 
  • Pathway to the brain: Spinal nerves< Thalamus< Somatosensory cortex at the front of the parietal lobes  
Vesticular (Balance) 
  • Sense Organ: Ear 
  • Stimuli: Changes in the body position and gravity 
  • Specialized Receptor Cells: Cilia (hair cells) in the semicircular canals 
  • Pathway to the brain: Vestibular< Nerves< Thalamus< Several brain regions including the parietal lobes 
Kinesthetic (Movement) 
  • Sense Organ: Joins, tendons, and muscles 
  • Stimuli: Muscle contractions 
  • Specialized Receptor Cells: Receptor cells located in joints, tendons, and muscles 
  • Pathway to the brain: Spinal Nerves< Thalamus< Somatosensory cortex at the front of the parietal lobes 


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