Sensation and perception sample question 1

hits and false alarms both increase, with sensitivity (d′) unchanged.

Sensation and perception sample question 3

regeneration of photopigment in the rods.

Sensation and perception sample question 4

adopted a more conservative response criterion.

Sensation and perception sample question 5

Unattended input is weakened rather than blocked, so highly relevant items such as one's name can still reach awareness.

MCAT · Psychological, Social, and Biological Foundations of Behavior · Psychology

Sensation and perception

Sensation and perception is part of Psychology in the MCAT Psychological, Social, and Biological Foundations of Behavior section. The questions below are written in the style of the real test, each with the answer and a worked explanation.

Question types you will see here include signal detection: criterion versus sensitivity, weber fraction prediction, top-down versus bottom-up processing and sensory adaptation versus habituation.

Common traps: reading a shift in overall yes-responses as better sensitivity; counting false alarms as misses; assuming a payoff change alters sensitivity rather than the criterion.

Sample questions

Question 1
After a warning about missed fractures, a radiologist begins calling ambiguous X-rays "positive" more readily, while her ability to tell fractures from normal bone is unchanged. According to signal detection theory:
- A.
  hits and false alarms both increase, with sensitivity (d′) unchanged.
- B.
  hits increase and false alarms decrease, because d′ has risen.
- C.
  hits and false alarms both decrease, because her criterion is stricter.
- D.
  misses increase, with sensitivity (d′) unchanged.
Answer: A. hits and false alarms both increase, with sensitivity (d′) unchanged.
A more liberal criterion shifts responses toward "yes," raising both hits and false alarms without changing d′ (A). B describes improved sensitivity, C describes a stricter criterion, and D reverses the effect, since saying yes more often reduces misses.
Question 2
After bumping an elbow on a table, a person rubs the sore area and finds that the pain lessens. This relief is best explained by:
- A.
  opponent-process theory
- B.
  gate control theory
- C.
  Weber's law
- D.
  top-down processing
Answer: B. gate control theory
Gate control theory proposes that input from large touch and pressure fibers can close a neural gate in the spinal cord that reduces the transmission of pain signals, which is why rubbing an injured area eases pain. Weber's law describes how the just-noticeable difference scales with stimulus magnitude and does not explain pain relief.
Question 3
After walking from bright sunlight into a dim cinema, a viewer can see very little at first but can make out seats after several minutes, and the improvement continues for about half an hour. The slow part of this improvement reflects:
- A.
  dilation of the pupil, which admits more light.
- B.
  a shift from using the cones to using the fovea.
- C.
  adaptation of the cones, which takes about 30 minutes.
- D.
  regeneration of photopigment in the rods.
Answer: D. regeneration of photopigment in the rods.
Bright light bleaches rhodopsin, and the rods, which support dim-light vision, recover sensitivity only as the pigment is regenerated over 20 to 30 minutes, the slow phase of dark adaptation. Pupil dilation happens within seconds and cones adapt within a few minutes, and the fovea contains the cones, so B describes no real shift.
Question 4
A radiologist learns that a particular type of tumor is far rarer than she had believed. Afterward, she reports fewer tumors both on scans that contain them and on scans that do not, while her ability to distinguish the two types of scans is unchanged. In signal detection terms, she has:
- A.
  increased her sensitivity (d').
- B.
  adopted a more liberal response criterion.
- C.
  adopted a more conservative response criterion.
- D.
  lowered her absolute threshold for detecting tumors.
Answer: C. adopted a more conservative response criterion.
Fewer hits and fewer false alarms together, with no change in discriminability, indicate a more conservative criterion: she now requires more evidence before reporting a tumor. A more liberal criterion would increase both hits and false alarms, and sensitivity is stated to be unchanged.
Question 5
At a crowded reception in Lagos, Tunde attends closely to one conversation, yet he turns at once when someone in another group says his name. He cannot report anything else that group said. Which conclusion does this best support?
- A.
  Unattended input is fully blocked before its meaning is analysed, just as an early all-or-none filter would predict.
- B.
  Unattended input is weakened rather than blocked, so highly relevant items such as one's name can still reach awareness.
- C.
  Tunde was dividing attention equally between the two conversations throughout.
- D.
  Hearing his name reflects sensory adaptation to the voices in his own conversation.
Answer: B. Unattended input is weakened rather than blocked, so highly relevant items such as one's name can still reach awareness.
B: noticing his own name means unattended speech was analysed for meaning, but recalling nothing else means it was attenuated, as in attenuation models. A cannot explain detecting his name. C conflicts with his recalling nothing else from that group. D: adaptation would reduce responses to constant input, not explain detecting a meaningful word.

Find your real gaps

A few questions show the style. The free scan shows which MCAT skills cost you the most points, then builds a plan around them.

Take the free scan