Question 1

Ordinarily we need to know not only what something is,but also where it is.Because vision doesn't give us this information directly,we must infer it.Explain five of the visual cues listed in the textbook.

Accepted Answer

A good answer will include five of the following key points.
- Convergence-The eyes turn inward when looking at a close object;the degree of convergence corresponds to the closeness of the object.
- Retinal disparity-The two eyes see slightly different images of the world;this difference can be used to infer depth.
- Interposition-Closer objects partially block our view of more distant objects.
- Linear perspective-When two parallel lines are viewed receding into the distance,they appear to converge.
- Light and shadow-Light and shadow give objects the appearance of three dimensions.
- Motion parallax-When an observer is moving,objects appear to move at different speeds and in different directions depending on their distance from the observer.
- Relative size-The smaller an object's image on the retina,the farther away the object appears.
- Texture gradients-Distant parts of a uniform surface appear denser;that is,its elements seem spaced more closely together.
- Height in plane-Objects that are higher in our visual field are perceived as further away than objects low in our visual field.

Question 2

Humans can recognize approximately 10 000 different smells.Explain how this is possible,including a general description of the olfactory process.

Accepted Answer

A good answer will include the following key points.
- Olfaction begins with nasal airflow bringing in molecules that bind with receptors at the top of the nasal cavity.
- Within the nasal cavity is the olfactory epithelium,a thin layer of cells that are lined by sensory receptors called cilia,which are tiny hair-like projections that contain specialized proteins that bind with the airborne molecules that enter the nasal cavity.
- Despite the fact that we have only about 1000 different types of receptors,we can detect many more distinct odours.This is because odour molecules can simultaneously stimulate several receptors at once.It is the pattern of the stimulation,involving more than one receptor,which gives rise to the experience of a particular smell.
- The information is transmitted to the olfactory bulb,which is the brain's central region for processing smell.The olfactory bulb connects with several regions of the brain through the olfactory tract,including the limbic system (emotion)as well as regions of the cortex where subjective experience of pleasure (or disgust)occurs.

Question 3

Sound waves are collected by the outer ear and channelled down the auditory canal.Describe the major structures of the ear and describe the role each plays in the process of hearing.

Accepted Answer

A good answer will include the following key points.
- A sound wave enters the outer ear and strikes the eardrum,causing it to vibrate.
- This vibration is passed along to three tiny bones in the middle ear called the ossicles.
- The innermost bone transfers the vibrations to the fluid-filled cochlea of the inner ear.
- The hair cells on the basilar membrane in the cochlea back and forth as the fluid in the cochlea moves.
- This causes the hair cells to initiate a signal that is passed along to the auditory nerve,which carries the signal to the brain.

Exam 4: C: Sensation and Perception

Ordinarily we need to know not only what something is,but also where it is.Because vision doesn't give us this information directly,we must infer it.Explain five of the visual cues listed in the textbook.

Humans can recognize approximately 10 000 different smells.Explain how this is possible,including a general description of the olfactory process.

Sound waves are collected by the outer ear and channelled down the auditory canal.Describe the major structures of the ear and describe the role each plays in the process of hearing.