5.1- How Do We Sense and Perceive the World Around Us?

Question 1

Sensation definition

Answer 1

• The detection of physical stimuli and transmission of that information to the brain.
• Physical stimuli can be light or sound waves, molecules of food or odor, or temperature and pressure changes.
• Sensation is the basic experience of those stimuli. It involves no interpretation of what we are experiencing.

Question 2

Perception definition

Answer 2

• The brain’s further processing, organization, and interpretation of sensory information
• Whereas the essence of sensation is detection, the essence of perception is the construction of useful and meaningful information about a particular sensation.

Question 3

Example of sensation vs. perception

Answer 3

• You drive up to a traffic signal as the light turns green. The light is detected by specialized neurons in your eyes, and those neurons transmit signals to your brain.
• As a result of these steps, you have sensed a stimulus: light
• When your brain processes the resulting neural signal, you experience the green light and register the meaning of the signal
• As a result of these additional steps, you have perceived the light and signal

Question 4

Picture showing the difference between sensation and perception

Answer 4

Question 5

Bottom-up processing

Answer 5

• Based on the physical features of the stimulus
• As each sensory aspect of a stimulus is processed, the aspects build up into perception of that stimulus
• You recognize a splash of root beer based on your experience of the scent, moisture, and taste

Question 6

Top-down processing

Answer 6

• How knowledge, expectations, or past experiences shape the interpretation of sensory information
• That is, context affects perception: What we expect to see (higher level) influences what we perceive (lower level)
• E.g. we are unlikely to see a blue, apple-shaped object as a real apple because we know rom past experience that apples are not blue

Question 7

Transduction

Answer 7

• Our sensory systems translate the physical properties of stimuli into patterns of neural impulses
• The different features of the physical environment are coded by activity in different neurons
• E.g. a green stoplight will be coded by a particular neural pattern in part of the eye being processed by areas of the brain involved in perceiving visual information
• Transduction is the translation of stimuli

Question 8

Example of transduction

Answer 8

• When a hand touches a hot skillet, that information must be sent to the brain
• The brain cannot process the physical stimuli directly, so the stimuli must be translated into signals that the brain can interpret

Question 9

Explain how transduction involves sensory receptors

Answer 9

• The sensory receptors receive stimulation - physical stimulation in the case of vision, hearing, and touch and chemical stimulation in the case of taste and smell
• The sensory receptors then pass the resulting impulses to the brain in the form of neural impulses

Question 10

Diagram showing the primary sensory areas of the brain

Answer 10

Question 11

Primary sensory areas

Answer 11

• These are the primary brain regions where information about vision, hearing, smell, and touch are projected
• Each sense organ contains receptors designed to detect specific types of stimuli
• E.g. receptors in the visual system respond only to light waves and can signal only visual information

Question 12

Example of sensory pathway for vision and hearing

Answer 12

Vision
- Stimuli: light waves
- Receptors: Light-sensitive rods and cones in retina of eye
- Pathways to the brain: optic nerve

Hearing:
- Stimuli: sound waves
- Receptors: pressure-sensitive hair cells in the cochlea of the inner ear
- Pathways to the brain: auditory nerve

Question 13

Diagram explaining qualitative vs. quantitative information

Answer 13