MCAT Social and Behavioral Sciences : Environment and Sensation

Study concepts, example questions & explanations for MCAT Social and Behavioral Sciences

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Example Questions

Example Question #3 : Visual Receptors

Which of the following photoreceptor cell is most sensitive to light?

Possible Answers:

Rods

Cones

Photosensitive retinal ganglion cells and cones

Photosensitive retinal ganglion cells

Correct answer:

Rods

Explanation:

“Rods” are incredibly sensitive to light, and can be triggered by a single photon. These cells are the primary photoreceptor cells active at very low light. The activation of cone cells requires significantly larger amounts of photostimulation; therefore, they function primarily in interpreting visual information in bright light. Photosensitive retinal ganglion cells, a group of cells that make up a very small percentage of overall photoreceptor cells, are less sensitive to photons and have a slower response time than either rods or cones.

Example Question #4 : Visual Receptors

Which of the following is not a type of photoreceptor cell?

Possible Answers:

Photosensitive retinal ganglion cells 

None of these

Rods

Cones

Correct answer:

None of these

Explanation:

There are three types of photoreceptor cells in the retina: “rods,” “cones,” and “photosensitive retinal ganglion cells.” While rods and cones directly communicate information about sight (e.g. contrast, brightness, and color), photosensitive retinal ganglion cells do not directly communicate visual information to the brain. Rather, they are involved in the pupillary reflex.

Example Question #1 : Processing And Integrating Visual Signals

Myopia is a very common condition. What is myopia and which type of lens can correct it?

Possible Answers:

Farsightedness; convex (i.e. converging) lens

Farsightedness; concave (i.e. diverging) lens

Nearsightedness; concave (i.e. diverging) lens

Nearsightedness; convex (i.e. converging) lens

None of these

Correct answer:

Nearsightedness; concave (i.e. diverging) lens

Explanation:

Myopia is nearsightedness, meaning the focal length is too short. This can be caused by too much refraction at the eye's lens or if the eyeball is too long. Myopia can be corrected using a concave (i.e. diverging) lens, which will increase the focal length as shown in the figure. 

Myopia diagram

Example Question #2 : Processing And Integrating Visual Signals

Signal detection studies measure an individual’s ability to detect certain stimuli. They involve exposure to stimuli at varying magnitudes and ask subjects to detect any changes in their perceptual experience of the stimuli (i.e. the just-noticeable difference). Perceiving magnitude differences in stimuli depends on the type of sensory experience (e.g. touch or sound) and is based on proportional rather than absolute amounts. 

Imagine a hypothetical study that asked participants to perceive changes in amplitude of a sound stimulus. In this experiment, the researchers wanted to know how much the amplitude needed to change in order for an individual to detect a difference. They decided to test the just-noticeable difference at three different amplitudes: low, medium, and high. Participants in each category listened to the initial sound, and then the amplitude was increased or decreased slightly until participants detected a difference. 

The researchers found that the absolute difference in amplitude that needed to occur in order for participants to detect a difference varied by condition (i.e. low, medium, high amplitude). This observation best illustrates which of the following? 

Possible Answers:

Sensory adaptation because as the body is continually exposed to a stimulus, the nerve receptors fire more frequently. 

Weber's law because the just-noticeable difference necessary to detect a change in the magnitude of a comparison stimulus is always half the magnitude of the initial stimulus. 

Sensory adaptation because as the body is continually exposed to a stimulus, the nerve receptors fire less frequently. 

Weber's law because the just-noticeable difference necessary to detect a change in the magnitude of a comparison stimulus (i.e., the amplitude) is a constant proportion of the initial stimulus. 

Correct answer:

Weber's law because the just-noticeable difference necessary to detect a change in the magnitude of a comparison stimulus (i.e., the amplitude) is a constant proportion of the initial stimulus. 

Explanation:

Weber's law states that the change in a stimulus that will be just noticeable is a constant ratio of the original stimulus. Because the original stimulus changes in each condition (i.e. low, medium, high), the ratio for the just-noticeable difference also changes; therefore, the magnitude necessary to detect a change will vary by condition. 

Example Question #21 : Environment And Sensation

Approximately what percent of the total sensory receptors of the body are in the eyes?

Possible Answers:

Correct answer:

Explanation:

The eyes contain approximately seventy percent of the total sensory receptors of the body. Most of these are located in the retina, which has up to 200,000 photoreceptor cells per square millimeter in its densest location (i.e. the fovea centralis).

Example Question #1 : Processing And Integrating Auditory Signals

George is speaking with his friends after the school football game. His attention is focused on their conversation, but suddenly he turns to the group next to him because he hears his brother's name mentioned. 

Which of the following concepts best accounts for George hearing his brother's name?

Possible Answers:

Primacy effect

Divided attention

Schemas

Heuristics

Cocktail party effect

Correct answer:

Cocktail party effect

Explanation:

The “cocktail party effect” accounts for the fact that we are able to hear personally important information even if we are not involved with it. In this example, George was in a conversation amongst his friends, and not involved with the conversation of the group nearby. The cocktail party effect explains that even though he was not directly paying attention to the nearby conversation, he did not completely filter the information out. Instead, it is was if he "turned the volume down" and paid attention once the information became personally relevant, such as the mentioning of his brother's name.

“Divided attention” is when an individual focuses on multiple tasks at once. While it could be argued that George is attending to two conversations at once, the cocktail party effect best describes the reason he is able to hear his brother's name without any attempt to listen to two conversations at once. The “primacy effect” concerns our tendency to have better memory for things at the beginning of a list (e.g. if you are given a list of words to remember, you will be more likely to remember the ones at the beginning rather than ones in the middle of the list). “Heuristics” are short cuts used for problem solving. Last, “schemas” are mental frameworks we use for understanding new experiences.

Example Question #2 : Hearing

Signal detection studies measure an individual’s ability to detect certain stimuli. They involve exposure to stimuli at varying magnitudes and ask subjects to detect any changes in their perceptual experience of the stimuli (i.e. the just-noticeable difference). Perceiving magnitude differences in stimuli depends on the type of sensory experience (e.g. touch or sound) and is based on proportional rather than absolute amounts. 

Imagine a hypothetical study that asked participants to perceive changes in amplitude of a sound stimulus. In this experiment, the researchers wanted to know how much the amplitude needed to change in order for an individual to detect a difference. They decided to test the just-noticeable difference at three different amplitudes: low, medium, and high. Participants in each category listened to the initial sound, and then the amplitude was increased or decreased slightly until participants detected a difference. 

Which of the following is most likely to be a potential confounding variable in the study 

Possible Answers:

Depressive symptomatology

Intelligence quotient

Marital status

Age

Correct answer:

Age

Explanation:

A confounding variable is an extraneous variable that is inadvertently associated with the independent or dependent variables. The just-noticeable difference of a stimulus can change substantially over the course of a person's lifespan. In this case, age is associated with differences in hearing abilities. Normative hearing loss and certain medical conditions that contribute to hearing loss are more common as age increases. The other options (marital status, IQ, and depressive symptoms) are not associated with changes in hearing. 

Example Question #8 : Hearing

In which lobe of the brain is the primary auditory cortex located?

Possible Answers:

Temporal lobe

Frontal lobe 

Parietal lobe

Occipital lobe

Correct answer:

Temporal lobe

Explanation:

The primary auditory cortex, the area of the brain responsible for processing auditory information, is located bilaterally in the temporal lobes in Brodmann areas 41 and 42. 

Example Question #1 : Other Senses And Sensation Principles

In early infancy, movement is almost entirely considered to be which of the following?

Possible Answers:

Autonomic

Reflexive

Exploratory

All of these

Functional

Correct answer:

Reflexive

Explanation:

When we are infants, our movements are almost exclusively reflexive—healthy babies demonstrate the same general response to a specific type of stimuli. While most of these movements are technically functional (i.e. the rooting reflex serves the function of aiding in child in being able to eat), not all serve a specific purpose.

On the other hand, "autonomic" does not apply to movement, but rather to unconscious actions that keep our bodies in homeostasis, like our breathing. Very young infants have not yet developed the nervous system capabilities that allow for exploratory movements.

Example Question #1 : Sensory Threshold And Weber's Law

Signal detection studies measure an individual’s ability to detect certain stimuli. They involve exposure to stimuli at varying magnitudes and ask subjects to detect any changes in their perceptual experience of the stimuli (i.e. the just-noticeable difference). Perceiving magnitude differences in stimuli depends on the type of sensory experience (e.g. touch or sound) and is based on proportional rather than absolute amounts. 

Imagine a hypothetical study that asked participants to perceive changes in amplitude of a sound stimulus. In this experiment, the researchers wanted to know how much the amplitude needed to change in order for an individual to detect a difference. They decided to test the just-noticeable difference at three different amplitudes: low, medium, and high. Participants in each category listened to the initial sound, and then the amplitude was increased or decreased slightly until participants detected a difference. 

The researchers found that for the low amplitude condition, increasing the amplitude by ten decibels resulted in participants noticing a difference half of the time (the other half of the time, they did not detect a difference between the two stimuli). The researchers can make which of the following conclusions?

Possible Answers:

The researchers can conclude that they identified the just-noticeable difference for the low condition because just-noticeable difference is defined as the amount by which a stimulus needs to change for a human to perceive a difference at least 50% of the time.

The researchers cannot conclude that they identified the just-noticeable difference for the low condition because just-noticeable difference is defined as the amount by which a stimulus needs to change for a human to perceive a difference 100% of the time. 

The researchers can conclude that they identified the just-noticeable difference for the low condition because just-noticeable difference is defined as the amount by which a stimulus needs to change for a human to perceive a difference at least 25% of the time. 

The researchers cannot conclude that they identified the just-noticeable difference for the low condition because just-noticeable difference is defined as the amount by which a stimulus needs to change for a human to perceive a difference at least 75% of the time. 

Correct answer:

The researchers can conclude that they identified the just-noticeable difference for the low condition because just-noticeable difference is defined as the amount by which a stimulus needs to change for a human to perceive a difference at least 50% of the time.

Explanation:

The just-noticeable difference is the amount that the stimulus needs to change in order for a human to perceive a difference half of the time or more. In this case, participants in the low amplitude condition were able to identify a difference half of the time when the amplitude was increased by ten decibels.

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