Sensation and Perception

Question 1

What does the Weber-Fechner Law posit about the change in weight placed into a patient’s hand to provide a just-noticeable difference?

Answer 1

A constant ratio of the original stimulus.

For example, if the patient only notices a difference when 500 g is changed to 1000 g, then he or she will next notice a difference at 2000 g.

Question 2

True or false.

Weber’s law posits that, if the smallest difference in sound noticed by a person at a given level is 2 dB, that just-noticeable difference of 2 dB will remain constant across all intensity levels.

Answer 2

false

Weber’s law posits that the just-noticeable difference is a constant ratio, not a constant value. Therefore, the just-noticeable difference will not be 2 dB across the board, but rather will depend on the decibel level of the original sound.

Question 3

A person is carrying a 6-kg grocery bag, to which her friend is gradually adding more items. The person notices the added weight once 0.6 kg has been added. If that person were instead to hold an 8-kg bag, what would be the just-noticeable difference?

Answer 3

0.8 kg

The original just-noticeable difference was (0.6 kg) / (6 kg) = 0.1 = 10%. A 10% increase from 8 kg is 0.8 kg. This is a very typical Weber’s law question.

Question 4

Which senses are subject to Weber’s law?

Answer 4

all senses

(vision, hearing, taste, smell, and touch)

Technically, Weber’s law doesn’t hold perfectly true at very small or very large intensity levels, but at moderate intensities, it can apply to essentially anything.

Question 5

Fill in the blank.

The _________ threshold is the lowest level of stimulus intensity which the body can detect.

Answer 5

absolute

Question 6

Fill in the blank.

The _______ threshold is the amount that stimulus intensity must be changed in order for a difference to be noticeable by the person.

Answer 6

difference

Question 7

A resident leaving a shift is walking to her car through a dark garage at night. Fearful of the desolate setting, she notices faint sounds she had not heard when she arrived in the morning. What theory is best illustrated by this example?

Answer 7

signal detection theory

Signal detection theory posits that our ability to detect stimuli is impacted by the intensity of the stimulus and the physical/psychological state of the individual.

Question 8

Fill in the blank.

In the context of signal detection, when a subject correctly identifies that a signal is present, this is termed a ______.

Answer 8

hit

A hit occurs when a signal (such as a flash of light in an experiment) is present and the subject accurately identifies it as such.

Question 9

Fill in the blank.

In the context of signal detection, if a subject identifies a signal as present, but no signal had been presented at all, this is termed a ______.

Answer 9

false alarm

A false alarm occurs when a signal is absent (for example, no light is flashed in an experiment), but the subject falsely identifies the signal as being present.

Question 10

Fill in the blank.

In the context of signal detection, if no signal is presented and the subject says “I didn’t see anything,” this is termed a ______ ______.

Answer 10

correct rejection

A correct rejection occurs when a signal is absent (for example, no light is flashed in an experiment), and the subject correctly identifies the signal as being absent.

Question 11

Fill in the blank.

In the context of signal detection, if a signal is presented and the subject says “I didn’t see anything,” this is termed a ______.

Answer 11

miss

A miss occurs when a signal (such as a flash of light in an experiment) is present, but the subject mistakenly identifies it as absent.

Question 12

In the 1980’s, religious fundamentalists in America protested bands like Led Zeppelin and Judas Priest, charging the bands with hiding Satanic messaging in their music that could not be consciously perceived by listeners. What concept does this exemplify?

Answer 12

subliminal stimulation

It is sensory stimulation that is below the threshold for conscious perception. (Obviously, these bands were not actually hiding Satanic messaging in their lyrics, but the concept that was being complained about was subliminal stimulation.)

Question 13

Define:

sensation

Answer 13

It is the process by which human sensory receptors and the nervous system receive and represent stimuli from the environment.

Question 14

Define:

perception

Answer 14

It is the process by which the body organizes and interprets sensory information, allowing recognition of meaningful stimuli.

For the MCAT, remember that sensation and perception are different concepts!

Question 15

A subject sees this image and thinks, “okay, I see ears, I see two circular eyes, I see stripes…oh, this must be a tiger.” What form of processing does this exemplify?

Answer 15

bottom-up processing

This process begins with sensory receptors and works up to the CNS, integrating the sensory input. Bottom-up processing usually involves detecting individual features first and later piecing them together into a coherent whole.

Question 16

A motorist is driving down the highway, looking for a place to stop for the night. He sees the sign below and pulls into the parking lot. He was able to recognize his destination as a motel due to what form of processing?

Answer 16

top-down processing

Top-down processing is data processing that is guided by high-level mental processes, such as when an individual draws on experience and expectations in order to form an overall perception. It is often exemplified by situations in which a person quickly recognizes an object without being able to discern all of its parts.

Question 17

A medical student enters a patient’s room and recoils from the smell of feces. The attending physician, already in the room for 30 minutes, asks the medical student what is wrong, as she does not notice the smell. What adjustment has the olfactory system of the attending undergone?

Answer 17

Sensory adaptation

Sensory adaptation is a change over time in the responsiveness of the sensory system to a constant stimulus, in this case diminished sensitivity to olfactory stimuli as a consequence of constant stimulation.

Question 18

Which type of receptor would be used to notice a flashlight at night?

Choose from gustatory receptors, thermoreceptors, mechanoreceptors, photoreceptors, nociceptors, baroreceptors, proprioceptors, and odorant receptors.

Answer 18

Photoreceptors

Photoreceptors are used in vision to detect light.

Question 19

Which type of receptor would be used to sense the smell of baby powder?

Choose from gustatory receptors, thermoreceptors, mechanoreceptors, photoreceptors, nociceptors, baroreceptors, proprioceptors, and odorant receptors.

Answer 19

Odorant receptors

Odorant receptors detect smell.

Question 20

Which type of receptor would be used to sense the presence of someone’s hand on your shoulder?

Choose from gustatory receptors, thermoreceptors, mechanoreceptors, photoreceptors, nociceptors, baroreceptors, proprioceptors, and odorant receptors.

Answer 20

Mechanoreceptors

Mechanoreceptors detect mechanical forces, including pressure on one’s shoulder.

Question 21

Which type of receptor would be used by a hand to sense an adjacent cold surface?

Choose from gustatory receptors, thermoreceptors, mechanoreceptors, photoreceptors, nociceptors, baroreceptors, proprioceptors, and odorant receptors.

Answer 21

Thermoreceptors

Thermoreceptors detect changes in temperature.

Question 22

Which type of receptor would be used when touching one’s finger to one’s nose with closed eyes?

Choose from gustatory receptors, thermoreceptors, mechanoreceptors, photoreceptors, nociceptors, baroreceptors, proprioceptors, and odorant receptors.

Answer 22

Proprioceptors

Proprioceptors are used to detect the position of one’s own body parts in space.

Question 23

Which type of receptor would be used to detect a painful needle prick?

Choose from gustatory receptors, thermoreceptors, mechanoreceptors, photoreceptors, nociceptors, baroreceptors, proprioceptors, and odorant receptors.

Answer 23

Nociceptors

Nociceptors are used to detect painful stimuli.

Question 24

Which type of receptor would be used to detect elevated systolic blood pressure?

Choose from gustatory receptors, thermoreceptors, mechanoreceptors, photoreceptors, nociceptors, baroreceptors, proprioceptors, and odorant receptors.

Answer 24

Baroreceptors

Baroreceptors detect changes in pressure.

Question 25

Which lobe of the brain is most closely associated with vision?

Answer 25

occipital lobe

The occipital lobe, located at the back of the brain above the cerebellum, is most closely associated with vision. The visual cortex is found in this lobe.

Question 26

Identify:

Ocular structure A in this image.

Answer 26

cornea

See the diagram above for the identities of all labeled structures.

Question 27

Identify:

Ocular structure B in this image.

Answer 27

pupil

See the diagram above for the identities of all labeled structures.

Question 28

Identify

Ocular structure C in this image.

Answer 28

lens

See the diagram above for the identities of all labeled structures.

Question 29

Identify

Ocular structure D in this image.

Answer 29

iris

See the diagram above for the identities of all labeled structures.

Question 30

Identify:

Ocular structure E in this image.

Answer 30

retina

See the diagram above for the identities of all labeled structures.

Question 31

Identify:

Ocular structure F in this image.

Answer 31

fovea

See the diagram above for the identities of all labeled structures.

Question 32

Identify:

Ocular structure G in this image.

Answer 32

macula

See the diagram above for the identities of all labeled structures.

Question 33

Identify:

Ocular structure H in this image.

Answer 33

optic nerve

See the diagram above for the identities of all labeled structures.

Question 34

Identify:

Ocular structure I in this image.

Answer 34

vitreous humor or vitreous gel

See the diagram above for the identities of all labeled structures.

Question 35

Fill in the blank.

The variable-sized opening of the eye into which light enters is the ____.

Answer 35

pupil

The pupil can be identified as the black region in the center of the iris, or colored portion of the eye.

Question 36

Fill in the blank.

The activation of the sympathetic nervous system causes the pupil of the eye to ____.

Answer 36

dilate

To remember this, recall that the sympathetic nervous system is the “fight-or-flight” system. When under extreme stress (for instance, when one is running away from a bear), a person needs dilated pupils to let in as much light as possible to facilitate vision.

Question 37

Fill in the blank.

Constriction, or narrowing, of the pupils is associated with the activation of the ___________ nervous system.

Answer 37

parasympathetic

Just as sympathetic activation causes pupil dilation, parasympathetic (“rest and digest”) activation causes pupil constriction.

Question 38

What term refers to the ring of muscle that forms the colored portion of the eye and regulates pupil size?

Answer 38

iris

Question 39

What term refers to the biconvex structure behind the pupil that changes shape to help focus light on the retina?

Answer 39

lens

In MCAT physics, you will see the lens of the eye mentioned frequently as an example of a convex lens.

Question 40

What is the name of the decussating (crossed) structure which serves as the neural pathway for visual information from the environment to the primary visual cortex in the occipital lobe?

Answer 40

optic chiasm

Question 41

What term refers to the aspect of perceived color that is determined by the wavelength of light that hits the eye?

Answer 41

hue

Question 42

What term refers to the amount of energy in a light or sound stimulus, which our senses perceive as brightness or loudness?

Answer 42

intensity

Question 43

Which term describes the adjustment of the shape of the lens to allow the eye to focus on close or distant objects?

Answer 43

accommodation

Question 44

Name the two structures of the eye that are most closely involved in accommodation.

Answer 44

1. ciliary muscle
2. suspensory ligaments

In accommodation, the ciliary muscle contracts, pulling the suspensory ligaments and thereby adjusting the shape of the lens of the eye.

Question 45

Identify:

The difference in perception of the two images below is one of:

Answer 45

acuity

Acuity is the sharpness, or clarity, of the images the eye perceives.

Question 46

Define:

hyperopia

Answer 46

It is an eye condition in which light is focused behind, instead of on, the retina, causing near objects to appear blurry and distant objects to appear normal.

Hyperopia is also known as farsightedness.

Question 47

What vision problem is shown in the eye below?

Answer 47

nearsightedness

(myopia)

It is an eye condition in which light focuses in front of, instead of on, the retina, causing distant objects to be blurry while closer objects appear normal.

Question 48

What type of lens would be used to correct the visual problem shown below?

Answer 48

diverging lens

In myopia, light converges before the retina; essentially, the lens of the eye is too strong. Utilizing a diverging lens would “cancel out” this excess convergence and correct the problem.

While this may seem like a physics question, myopia could be asked about in the context of physics or psychology. It is important that you understand topics like this one in both contexts for MCAT success.

Question 49

Name the primary retinal receptors used to view an object at twilight, when ambient light is low.

Answer 49

rods

Rods are retinal receptors that detect black vs. white and are necessary for peripheral and low-light vision.

Question 50

Name the pigment in rods that allows for the sensation of light and dark.

Answer 50

rhodopsin

Question 51

Name the only photoreceptor type found at the fovea, which is responsible for color detection by the eye.

Answer 51

cones

Cones are active at high light levels (photopic vision). These receptors are capable of color vision and are responsible for high spatial acuity.

Question 52

What term describes the light levels at which both rods and cones are operational?

Answer 52

mesopic lighting

Most nighttime outdoor and traffic lighting scenarios are in the mesopic range.

Question 53

At which point does the optic nerve exit the eye, making visual perception at that point impossible?

Answer 53

blind spot

Question 54

Name the specialized nerve cells in the brain which allow one to detect the shape differences between the objects below.

Answer 54

Feature detectors

Feature detectors are nerve cells in the brain that respond to the specific features of a stimulus, such as angle, shape, or movement.

Question 55

Which type of sensory processing allows an individual to watch a video of a car and identify the shape of the car, perceive the car’s movement, and deduce the fact that the car is getting closer to the camera, all at the same time?

Answer 55

parallel processing

Parallel processing is the processing of multiple stimuli or the addressing of multiple aspects of a problem simultaneously. This is important in vision, where the brain divides what it sees into color, depth, motion, and shape.

Question 56

Arrange the following components of the auditory pathway into their correct sequence from the cochlea to the brain.

1. Auditory cortex
2. Auditory nerve
3. Cochlear nuclei
4. Inferior colliculus
5. Superior olivary complex
6. Medial geniculate nucleus

Answer 56

The correct pathway is:

2 (auditory nerve) → 3 (cochlear nuclei) → 5 (superior olivary complex) → 4 (inferior colliculus) → 6 (medial geniculate nucleus) → 1 (auditory cortex)

Question 57

What are the three main parts of the ear?

Answer 57

1. external ear
2. middle ear
3. inner ear

Question 58

Fill in the blank.

The ______ ear collects sound waves and funnels them down the ear canal, where they vibrate the tympanic membrane.

Answer 58

external

Question 59

Fill in the blank.

Within the _____ ear, the eardrum is connected to the ____.

Answer 59

middle, ossicles

Question 60

Fill in the blank.

The ossicles are the smallest bones in the body, which mechanically carry sound waves to the _____ ear.

Answer 60

inner

Question 61

Fill in the blank.

The _____ connects the middle ear to the nasopharynx, equalizing the air pressure within to that of the surrounding environment.

Answer 61

Eustachian tube

Question 62

Fill in the blank.

The _____ ear contains the _____, the specialized organ that converts sound waves into nerve impulses.

Answer 62

inner, cochlea

Question 63

Fill in the blank.

The nerve impulses from the cochlea are carried to the brain via the _____ nerve.

Answer 63

auditory nerve

Question 64

Fill in the blank.

Coiled within the inner structure of the cochlea, the _____ ___ _____ contains the cells responsible for hearing.

Answer 64

Organ of Corti

Question 65

Name the two main types of hair cells located in the cochlea of the inner ear.

Answer 65

1. inner hair cells
2. outer hair cells

Question 66

Which specialized auditory cells are cylindrical in shape and have stereocilia at the top of the cell and a nucleus at the bottom?

Answer 66

outer hair cells

When the stereocilia (hairs) are bent in response to a sound wave, an electromotile response occurs.

Question 67

What term refers to sensation other than that associated with the five specialized senses?

Answer 67

Somatosensation

It is the process that conveys information regarding the body surface and its interaction with the environment. Somatosensation is separate from the five specialized senses (vision, etc.).

Question 68

What are the three specialized types of somatosensation, and what are their functions in sensory perception?

Answer 68

Somatosensation can be subdivided into:

1. Mechanoreception - discriminative touch.
2. Thermoreception - temperature perception.
3. Nociception - pain perception, which can be chemical, mechanical and/or thermal.

Question 69

Fill in the blank.

Taste can be detected via specialized sensory receptors called taste buds, which are primarily ________.

Answer 69

chemoreceptors

Chemoreceptors detect changes in the concentrations of certain chemicals.

Question 70

Which type of compound are scientists most likely to measure when studying the effects of chemical substances produced and released into the environment by males on female behavior in social settings?

Answer 70

Pheromones

It is any chemical substance produced and released into the environment by an animal that affects the behavior or physiology of other members of its species. This is most commonly observed in mating.

Question 71

When drinking water with a high sulfur content, people are told to hold their nose in order to reduce the bad taste of the water. What interaction does this exemplify?

Answer 71

sensory

Sensory interaction is the idea that one sense may influence another, as when the smell or color of food influences its taste.

Question 72

Name the five taste sensations detectable across the tongue.

Answer 72

1. bitter
2. sour
3. salty
4. sweet
5. umami

Question 73

Which sense most likely explains the strength and duration of the elite athletes who can often perform required movements at their peak levels, even years after retiring from their sport?

Answer 73

kinesthetic sense

This sense, sometimes called muscle memory, is the system for sensing the movement of individual body parts.

Question 74

Which term is typically used to refer to awareness of the body’s position in space, rather than awareness of movement, although some sources consider it essentially interchangeable with the kinesthetic sense?

Answer 74

Proprioception

For the MCAT, you should think of proprioception as the awareness of where one’s body parts are in space (even if stationary), while the kinesthetic sense refers more to the awareness of one’s movements.

Question 75

Which sense is highly developed in professional bull riders, allowing them to maintain an incredibly stable sense of balance and precise control over their position while riding?

Answer 75

vestibular sense

The vestibular sense is the awareness of body balance and movement. The sensations of body rotation and of gravitation and movement arise from hair cells in the inner ear.

Question 76

In many animals (including humans), deprivation of light stimuli while the animal is very young can permanently stunt the development of eyesight, even if access to light is restored later. What concept does this illustrate?

Answer 76

critical period

Put simply, a critical period is a period of time during development where a given sense or skill (such as vision or language) must develop; otherwise, it will never develop properly or fully.

Question 77

Which type of perceptual organization allows the brain to determine the outline of the vehicle below, even in low light?

Answer 77

Form perception

Form perception is the ability to recognize an object’s shape or outline.

Question 78

The ability to recognize that the vehicle in the image is moving close to the camera but is not actually changing size is due to which two perceptual approaches?

Answer 78

• motion
• constancy

Motion perception is the ability to recognize that an object is moving, while constancy is what allows the brain to understand that attributes of objects, such as color, size, and shape, are constant, even though the sensory information associated with some of these traits may change. For example, as the car approaches, it increases in size, yet we understand the car is not actually growing.

Question 79

Which form of perception allows one to determine how far away an object is?

Answer 79

Depth perception

Depth perception is the way in which we perceive how far away objects are. Essentially, depth perception allows us to view the world three-dimensionally.

Question 80

Fill in the blank.

Pieces of visual information that come from both eyes working together are known as _____ ____.

Answer 80

binocular cues

Here, “bi-“ means “two,” while “ocular” refers to the eyes.

Binocular cues include concepts such as the convergence of the two eyes on a given point in the field of vision. Such cues are required for proper depth perception.

Question 81

Fill in the blank.

If you close one eye, you can still gather some information about the distance of an object from you by assessing its movement relative to that of other objects in the field of view. Such pieces of information that can be gathered with one eye are ________ ____.

Answer 81

monocular cues

Here, “mono-“ means “one,” while “ocular” refers to the eyes. The specific monocular cue described on this card is motion parallax.

Question 82

Fill in the blank.

_______ principles are the set of human perception principles that help us interpret and group objects.

Answer 82

Gestalt

Examples of these principles include the law of similarlity, the law of closure, and many more.

Question 83

Fill in the blank.

Gestalt principles in psychology are oriented around the principle of _______.

Answer 83

Prägnanz

This principle states that, when presented with a set of elements that could be interpreted in multiple ways, people tend to perceive the simplest possible interpretation.

Question 84

Which Gestalt principle is illustrated by the image below?

Answer 84

proximity

This Gestalt principle states that objects or shapes close to one another appear to form groups. This occurs even when the shapes, sizes, and objects are radically different, so long as they are close to each other.

Question 85

Which Gestalt principle is illustrated by the image below?

Answer 85

similarity

This Gestalt principle states that, all else being equal, we perceive stimuli that physically resemble each other as part of the same object and stimuli that are different as part of different objects.

Question 86

Which Gestalt principle is illustrated by the image below?

Answer 86

closure

This Gestalt principle is the tendency to see complete figures or forms even if the object shown is incomplete or partially obstructed by other objects, or if information needed to make it complete is missing.

Question 87

Which Gestalt principle is illustrated by the image below?

Answer 87

continuation

This Gestalt principle states that when we view an image containing an intersection between two or more objects, we perceive each object as a single, uninterrupted object.

Question 88

MCAT practice exams typically allow students to scroll down their viewing window to see more of the passage or question. Synchrony between the movement of the scroll bar and the passage text illustrates which Gestalt principle?

Answer 88

common fate

This principle states that when visual elements are seen moving in the same direction at the same rate, perception associates the movement as part of the same stimulus. The principle of common fate is used extensively in computer user-interface design.