Sensation and Perception

1. Distinction between sensation and perception
   1. Sensation:
      1. is the process by which important changes in the state of the world create changes in the state of the brain.
      2. Proximal Sense
         1. Ex. Taste, Touch
      3. Distal Sense
         1. Ex. Smell, hear, see
   2. Perception:
      1. is the process by which changes in the state of the brain give rise to our conscious experience of the world.
2. Blindsight
   1. In blindsight, individuals have lost conscious awareness of visual information in a specific field due to damage to the primary visual cortex. They do not "see" anything in that area (perception is impaired).
   2. However, they can still respond to visual stimuli—such as guessing the direction of a moving object—indicating that their brain processes some visual information (sensation is still occurring).
3. “What” and “where” pathways
   1. Pathways of visual processing
      1. The “what” pathway (aka the Ventral pathway)
         1. Allows us to recognize and discriminate visual shapes and objects (eg, identify an object)
      2. The “where” pathway (aka the Dorsal pathway)
         1. Allows us to locate objects in space and act on this knowledge (eg, grab an object.
      3. Damage to the Ventral pathway
         1. Failure of visual perception
            1. Visual agnosia, Prosopagnosia (face blindness)
      4. Damage to the Dorsal pathway
         1. Failure of spatial perception
            1. Hemispatial Neglect, Optic ataxia
4. Visual Illusions
   1. Color Contrast Illusions:
      1. Illusions like the Hermann grid or the simultaneous contrast illusion demonstrate how the perception of color can change based on surrounding colors or patterns. The receptors detect changes in light and color contrasts, highlighting the role of relative differences rather than absolute values in our sensory experience.
      2. Here, the sensory system detects light intensity and color changes rather than just the raw colors themselves.
5. Weber’s Law
   1. is a principle in psychophysics that describes the relationship between the magnitude of a stimulus and the smallest detectable difference (or change) in that stimulus.
6. EX. If you are holding a lightweight (like a 1 kg object) and someone adds 100 grams, you might notice the difference. However, if you are holding a heavier weight (like 10 kg), you would need a greater weight added (around 1 kg) to notice the change. This demonstrates that the JND is proportional to the original weight.
7. Weber's Law suggests that our sensory systems are more sensitive to relative changes than to absolute changes. This is why we can often detect differences in stimuli when they are presented in varying contexts, rather than just considering their absolute values.
8. Idealism & Realism
   1. Idealism:
      1. posits that reality is fundamentally mental or immaterial. According to this view, the mind plays a crucial role in shaping our experiences and perceptions of the world.
   2. Realism:
      1. posits that reality exists independently of our perceptions and that our senses provide us with an accurate representation of the external world. It holds that there is an objective reality that can be observed and understood.
9. Phonemic Restoration
   1. is a fascinating phenomenon in auditory perception where listeners fill in missing sounds in speech based on context and prior knowledge. This process illustrates how our brains actively reconstruct incomplete auditory information.
10. *A classic demonstration involves sentences where a phoneme is replaced by a noise. For instance, if a listener hears "The eel was on the orange," they may perceive "The peel was on the orange," even if the initial "p" sound is masked. The context allows the listener to infer the missing sound.
11. Expectancy Effects
    1. refer to the phenomenon where a person's expectations about a stimulus can influence their perception of that stimulus. Numerous studies and experiments provide evidence for how expectations shape our sensory experiences.
12. For instance, a blurred image might be interpreted as food if the individual was previously exposed to food-related stimuli.
13. For example, if a listener expects a sentence to contain a particular word, they are more likely to perceive it correctly even if part of the sound is obscured.
14. Top-down and Bottom-up Processing
    1. are two fundamental approaches to understanding how we perceive and interpret sensory information.
    2. Bottom-Up Processing
       1. refers to perception that starts with the sensory input. It involves building up a perception from the smallest pieces of sensory information
15. Recognizing a face by observing its individual features (eyes, nose, mouth) and assembling these features into a complete image.
16. Identifying a song based solely on the notes and rhythms heard, without any knowledge of the song beforehand.
17. Top-Down Processing
    1. refers to perception that is driven by cognition. It involves using pre-existing knowledge, expectations, and context to interpret sensory information.
18. Reading a sentence with missing letters and still being able to understand it because the brain predicts what the missing letters are based on context.