MCAT Social and Behavioral Sciences : Sensory Threshold and Weber's Law

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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 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 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.

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.

Example Question #2 : Principles Of Sensation

Excerpt from “Two Kinds of Vocational Education” by Julius T. House, 1921

American Journal of Sociology, Vol. 27, No. 2 (Sep., 1921), pp. 222-225

               

There are two schools of thinkers interested in vocational education. One of these is individualistic, thinks in teams of fitting the child to the job, accepts the present economic system with little, if any, criticism. It would isolate consideration of the vocation, so far as possible, from consideration of its social purposes. Psychologically its plan is based upon habit, with no thought of developing in the child a sense of the relation of his work to the whole social process. To secure the result sought there must be early separation of technical schools from the rest of the school system. It is proposed to begin with the seventh grade, the so-called junior high school.

The purpose of the technical school is and will be to get the answer, already known to the teacher, by the shortest route. Emphasis will be laid on rapid calculation; swift, effective movement; automatic response. The typewriter, the shorthand notebook, the hammer and nail, the stove, the furnace, the retort, are the instruments of education. A technique of salesmanship and advertising, without the regard to the ethics of these operations and with no comprehension of the principles of psychology, is developed. Rough-and-ready adaptation to a rough-and-ready business world is the goal.

Certain results follow: (1) Even more rigid division of industrial life between two groups: those who manage, in whom power of initiative is vested; those who are skilled in narrow processes with no outlook upon the meaning of the work. (2) The exploitation of this isolated class. (3) The establishment of an institution to perpetuate this condition. Custom is already being instituted of sending the children of poor families to this manual-skill-producing school. (4) Public taxation to support institutions to assist business based on the supposition that when business prospers moral values take care of themselves.

The second group of thinkers, seemingly few but with men like John Dewey leading, are interested in vocational education as a means of introducing the child more intimately into the life of society. It is believed that such study should be directed to the perception of the relation of vocations to all the social process. Therefore all the students are to study all the vocations. The choice of a life-work will be, then, only a by-product of the training—important indeed, but still a by-product. Already such work is done in the grades. It remains only to enlarge it and relate it to the proper sciences as the later years of school life are reached.

The author argues that the working class will be continually exploited by the managing class. Suppose that one manager slowly decreases the hourly wage of his employees by $0.03 every month. The workers are bothered, but don’t feel that it effects them that much. Another manager outrages his employees by dropping the hourly wage by $0.40. Who developed a law of sensory perception that accurately models this scenario?

Possible Answers:

Durkheim

Cooley

Mead

Weber

Correct answer:

Weber

Explanation:

Max Weber developed the Weber’s law of sensory perception while studying human stimulus. This law  describes how a change in perception is proportional to the starting stimulus. For example, if a person holding a 50 pound weight cannot feel anything less than five pounds being added, then a person holding 100 pounds will not be able to feel anything less than 10 pounds being added. For the wage examples, one group was not disturbed because the amount of change was below their threshold of importance. 

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