21. Take your learning a step further by testing your critical thinking skills on this scientific problem solving exercise.

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Carlos, who is determined to quit smoking, today purchased a subliminal persuasion audio/videotape package. The booklet accompanying the tapes claims that subliminal suggestions "harness the power of the unconscious mind to [help you increase motivation to] quit smoking." Carlos is skeptical, but he decides to try the demonstration included on the videotape. The instructions are to turn off room lights, start the videotape, and stare at a fixation point (a plus sign that appears in the center of the television screen) until the screen goes blank. During the demonstration, which lasts about 5 minutes, Carlos occasionally perceives a flash of light on the screen just above the fixation point. Shortly after the screen goes blank, several geometric figures, including a square, a circle, a triangle, and a rectangle, appear above the question, "Which of these figures is most pleasing to you?" Although he is not sure why, Carlos picks the triangle. The tape ends with the following message: "If you picked the triangle, subliminal persuasion will work for you! During the demonstration, what appeared to be flashes of light were actually subliminal presentations of triangles. The triangles, which appeared too briefly to be perceived by your conscious mind, were perceived by your unconscious mind. Since familiarity breeds fondness, your unconsciousness persuaded you that smoking is unhealthy, unflattering, and something you definitely do not want to continue doing."

What assertions about subliminal persuasion are made in the booklet and videotape? Be sure to define all important concepts and terms as they are used in this example.

What evidence is presented that the subliminal suggestions will help Carlos quit smoking? Is this evidence trustworthy?

How else could you explain Carlos's preference for the triangle?

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Air traffic controllers face the difficult task of guiding pilots in making safe departures and landings. To complicate matters, at any moment several airplanes may be simultaneously approaching different runways at similar angles and altitudes while other airplanes are in various stages of taking off from nearby runways. To assist them in their task, the controllers monitor air traffic in two ways: (1) by visually observing from a high tower, and (2) by monitoring airplanes as they appear as "blips" on a radar screen.

The air traffic controller's task can be construed as a practical problem involving perceptual organization. For example, when the image of an airplane first appears in the sky or on the radar screen, it must be differentiated from other objects. Once it is recognized as an airplane, its distance, altitude, and angle of approach must be discerned.

Psychology offers principles of perceptual organization for grouping stimuli together into recognizable forms and for determining their distance. The principle of relative clarity, for example, states that hazy objects are perceived as farther away than sharp, clear objects. Can you envision how air traffic controllers use each of the following principles of perceptual organization? In framing your answers, first indicate what the principle enables air controllers to do and then say how this ability helps them.

Figure-ground:

Relative size:

Continuity:

Relative height: