AP Psychology: Sensation (Drill 6)

Question 1. A factory worker spends eight hours a day operating heavy machinery. After several months, she no longer consciously notices the loud hum of the machines during her shift, even though she hears it clearly when she first arrives. Co-workers visiting for the first time notice the noise immediately. What process best explains the worker's reduced awareness?

• A) Perceptual set, which causes people to interpret stimuli based on prior expectations
• B) Selective attention, which is the conscious decision to focus on relevant stimuli and ignore others
• C) Sensory adaptation, which is reduced sensitivity to a constant, unchanging stimulus over time ✓
• D) Signal detection, which explains how the worker's threshold for hearing has permanently increased

Explanation: Sensory adaptation is the reduced sensitivity that develops when a stimulus remains constant over time, exactly what the factory worker experiences. The fact that co-workers immediately notice the same noise confirms that the sound is detectable; it is the worker's adapted sensory system that accounts for her diminished awareness. (B) describes a real cognitive process, but selective attention involves a conscious, deliberate choice about what to focus on, the worker is not deciding to tune out the sound, which rules this out. (D) confuses adaptation with signal detection theory and incorrectly implies a permanent threshold shift; sensory adaptation is a temporary change in sensitivity, not a lasting structural change in the auditory system. [Practice 1]

Question 2. A researcher recruits 80 participants to study taste perception. Half receive a bitter-masking compound before tasting a series of foods; the other half taste the same foods without it. The researcher measures how many milligrams of a bitter substance each participant must detect before noticing it. The researcher concludes that the compound raises the threshold for bitter taste detection. In this study, what is the dependent variable?

• A) The type of foods presented during the tasting session
• B) The amount of bitter substance required for participants to detect bitterness ✓
• C) Whether participants received the bitter-masking compound or the control condition
• D) The number of taste buds on each participant's tongue

Explanation: The dependent variable is what the researcher measures as the outcome, here, the minimum amount of bitter substance each participant needs to detect a taste, which is the operational measure of detection threshold. (C) describes the independent variable: the presence or absence of the compound is what the researcher manipulates, not what is measured. (A) is accurate about the procedure, but the foods presented are part of the stimulus materials rather than the measured outcome, this choice describes how the study is run, not what it records. (D) is a plausible individual-difference variable that could potentially confound the results, but the study does not measure it. [Practice 2]

Question 3. A patient can detect faint tones in a quiet testing room but frequently misses sounds of the same volume in noisy environments. One audiologist says the patient's hearing is normal; another says the patient has a deficit. Which framework best explains why both could be drawing on valid evidence?

• A) Absolute threshold measures detection under controlled, quiet conditions and reflects a person's basic sensory sensitivity; signal detection theory explains why performance can differ in real-world noise even when the threshold is intact. ✓
• B) Absolute thresholds are measured in noisy environments, so both audiologists are working from the same data.
• C) Signal detection theory shows that absolute threshold measurements are clinically irrelevant; only hit rates and false alarm rates matter.
• D) The patient likely has sensorineural hearing loss, which affects performance in noise but not in quiet settings.

Explanation: Absolute threshold is defined under controlled, low-noise conditions, the intensity detected 50% of the time in an optimal setting, and the first audiologist is correct that this measure is normal. Signal detection theory goes further by separating sensory sensitivity from response bias and showing that real-world detection depends on the signal-to-noise ratio, not sensory capacity alone; this is what the second audiologist is pointing to. Both are right because they are using different but compatible frameworks. (D) is a plausible clinical interpretation, but it goes beyond what the evidence supports and does not address the conceptual question the stem is asking. (B) is factually wrong: absolute threshold testing is conducted under controlled quiet conditions, not in noise. [Practice 1]

Question 4. A researcher tests weight discrimination. Participants holding a 100-gram weight can reliably detect an added 2 grams. When the starting weight is increased to 200 grams, participants require an added 4 grams to detect a difference. These findings are most consistent with which principle?

• A) The absolute threshold, which specifies the minimum stimulus intensity detectable under ideal conditions
• B) Signal detection theory, which attributes detection accuracy to the ratio of signal strength to background noise in the case described here
• C) Sensory adaptation, which reduces sensitivity when a constant stimulus is maintained over time
• D) Weber's law, which states that the just-noticeable difference is a constant proportion of the original stimulus intensity ✓

Explanation: Weber's law predicts that the just-noticeable difference (JND) is a constant fraction of the baseline stimulus. Here the JND doubles from 2 grams to 4 grams as the starting weight doubles from 100 to 200 grams, the ratio holds at 2% in both cases, exactly as Weber's law predicts. (A) addresses a different question entirely: absolute threshold is about detecting a stimulus at all, not about discriminating between two stimuli that are both already above threshold. (B) is accurate as a framework but addresses the wrong phenomenon, signal detection theory explains how criterion-setting and sensitivity affect detection under uncertainty, not why discrimination thresholds scale proportionally with stimulus intensity. [Practice 3]

Question 5. A professor tells a class that patients with damage to a specific region of the somatosensory cortex lose sensation in their right hand but not their arm, torso, or face. A student asks why such localized damage affects only one body part. The professor's best explanation draws on which concept?

• A) Neuroplasticity, which describes the brain's ability to reorganize following damage
• B) The all-or-none principle, which describes how neurons fire completely or not at all
• C) Lateralization, which means the left hemisphere controls sensation for the right side of the body in this sensory example
• D) The cortical homunculus, which shows that each body region maps to a distinct area of the somatosensory cortex ✓

Explanation: The cortical homunculus is a somatotopic map in which each body part corresponds to a specific region of the somatosensory cortex, with more sensitive areas receiving proportionally larger cortical representation. Localized damage therefore produces localized sensory loss, in this case limited to the right hand, because the hand and arm map to entirely different cortical regions. (C) is accurate, the left hemisphere does process right-side sensation, but although this choice is correct, it does not explain why hand sensation is lost while arm and torso sensation remain intact; only somatotopic organization accounts for that specificity. (B) describes a principle of neural firing thresholds and has no bearing on how body regions are mapped across the cortex. [Practice 1]