Test: MCAT Social and Behavioral Sciences

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. 

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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?

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. 

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 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. 

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