MCAT Social and Behavioral Sciences : Detection Theory and Sensory Adaptation

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Example Question #1 : Detection Theory And Sensory Adaptation

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. 

Imagine that this study used a forced choice design in which participants had to select "the same" or "different" after hearing a pair of sounds at different amplitudes. As the amplitude of the comparison sound increased, which type of signal detection response would be most likely, regardless of the initial sound? 

Possible Answers:

Miss

False alarm

Correct rejection

Hit

Correct answer:

Hit

Explanation:

In forced-choice signal detection method, responses can be classified into four categories: miss (failing to identify a changed stimulus), false alarm (identifying an unchanged stimulus as changed), correct rejection (identifying an unchanged comparison as the same as the initial stimulus), or hit (correctly identifying a comparison stimulus that differs from the initial stimulus). As the amplitude is increased, it is also more likely that the subject would be able to correctly identify a changed stimulus. The greater the discrepancy in magnitude for the two sounds, the more likely the participant will get a hit. 

Example Question #2 : Detection Theory And Sensory Adaptation

Which of the following is an example of sensory adaptation?

Possible Answers:

Being able to see a candle flame at thirty miles on a dark clear night

None of these

Music at a concert seems less loud at the end of the night

Needing more of a drug to feel its effects after taking it for a while

Correct answer:

Music at a concert seems less loud at the end of the night

Explanation:

Sensory adaptation is the gradual alteration in sensitivity with prolonged stimulation or the absence of stimulation. Being able to see the candle flame is an example of "absolute threshold," which is the minimum intensity of a stimulus for humans to be able to detect the stimulus fifty percent of the time. Last, needing more of a drug to feel its effects is an example of tolerance.  

Example Question #3 : Detection Theory And Sensory Adaptation

What is the definition of a "just-noticeable difference"?

Possible Answers:

The amount by which a stimulus needs to change for a human to perceive a difference at least twenty-five percent of the time

The amount by which a stimulus needs to change for a human to perceive a difference at least sventy-five percent of the time

The amount by which a stimulus needs to change for a human to perceive a difference all of the time

The amount by which a stimulus needs to change for a human to perceive a difference at least firfty percent of the time

Correct answer:

The amount by which a stimulus needs to change for a human to perceive a difference at least firfty percent of the time

Explanation:

Just-noticeable difference (JND) is the amount that a stimulus needs to change for someone to be able to notice it at least half the time. For example, the JND needed to perceive that a light is brighter is a two percent change in the brightness of the light’s illumination. This means that when the brightness goes up by two percent, we would be able to notice a difference half of the time or more. 

Example Question #4 : Detection Theory And Sensory Adaptation

As a part of a research study, Carlos was presented with a sound. He was instructed to press "S" (for “same”) every time that he heard the same sound, and to press "D" (for “different”) every time he heard a different sound. At the end of the test, Carlos was informed that he correctly pressed "S" for every same sound, but incorrectly identified many of the different sounds as “same sounds.” Carlos' ability to detect signals would be described as which of the following?

Possible Answers:

Equal sensitivity and selectivity

Excellent sensitivity, but poor selectivity

Excellent selectivity, but poor sensitivity

None of these

Correct answer:

Excellent sensitivity, but poor selectivity

Explanation:

Sensitivity is the ability to detect a true signal. Carlos correctly identified all of the "S" sounds; however, he missed many of the "D" sounds, indicating that his selectivity is poor. In medicine, doctors desire that screening instruments (e.g. mammograms as a screening for breast cancer) have high sensitivity so that no cases or symptoms are missed. Selectivity is less important for screening. 

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