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MCAT Psych/Soc study materials
MCAT Psych/Soc study resources

MCAT Psych/Soc practice questions

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Question 1Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Weber's law predicts that the just noticeable difference for a stimulus is:

  1. a constant fraction of stimulus intensity Correct answer.
  2. largest near the middle of the sensory range
  3. independent of the sensory modality involved
  4. a fixed absolute amount regardless of intensity

Explanation

Weber's law states that the smallest detectable change is a constant proportion of the original stimulus, known as the Weber fraction. This means that as background intensity rises, a proportionally larger absolute change is required for detection. The relation holds reasonably well across the middle range of stimulus intensities within a modality.

Question 2Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Sensory transduction refers to:

  1. conversion of stimulus energy into neural signals Correct answer.
  2. the interpretation of sensory input using prior knowledge
  3. the decline in responsiveness after repeated stimulation
  4. the transmission of a signal along a sensory nerve

Explanation

Transduction is the process by which receptors convert physical or chemical stimulus energy into electrical signals the nervous system can use. Transmission, adaptation, and interpretation are separate stages that occur after or alongside transduction.

Question 3Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Several dots spaced closely together in rows are perceived as continuous lines rather than as separate dots. This illustrates the Gestalt principle of:

  1. common fate
  2. closure
  3. proximity Correct answer.
  4. continuity

Explanation

The principle of proximity holds that elements near one another tend to be grouped together perceptually. Because the dots are close, the visual system organizes them into rows rather than isolated points. Closure, continuity, and common fate describe different grouping rules.

Question 4Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Which receptor type is best suited for detecting a faint star in the night sky?

  1. Cones, because they adapt more slowly
  2. S-cones in the central retina
  3. Rod cells in the periphery Correct answer.
  4. Cones packed in the fovea

Explanation

Rod cells are extremely sensitive to low light and dominate peripheral vision, making them best for dim stimuli such as faint stars. Cones require higher light levels and support color and fine detail. Looking slightly off to the side places the star's image on rod-rich retina.

Question 5Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Staring at a red patch and then looking at a white surface produces a green afterimage. This is best explained by:

  1. place theory
  2. frequency theory
  3. trichromatic theory
  4. opponent-process theory Correct answer.

Explanation

Opponent-process theory proposes that color is coded by paired channels such as red-green and blue-yellow, which cannot be activated simultaneously. Prolonged stimulation of the red member of a pair leaves the green member relatively more active, producing a green afterimage.

Question 6Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

The minimum intensity of a tone that a listener can detect on 50 percent of presentations is called the:

  1. absolute threshold Correct answer.
  2. subliminal threshold
  3. difference threshold
  4. adaptation level

Explanation

The absolute threshold is the weakest stimulus intensity detectable about half the time under ideal conditions. The difference threshold concerns detecting a change between two stimuli rather than detecting a stimulus at all.

Question 7Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A patient with damage to the vestibular system would have the greatest difficulty with:

  1. detecting a light touch on the forearm
  2. distinguishing between similar shades of color
  3. locating the source of a faint sound
  4. keeping her balance while walking Correct answer.

Explanation

The vestibular system, including the semicircular canals and otolith organs, detects head position and acceleration and is essential for postural stability. Damage therefore disrupts balance and produces dizziness or unsteadiness. Color, sound localization, and touch depend on other systems.

Question 8Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Reading a physician's messy handwriting becomes easier once the patient's likely diagnosis is known. This best reflects:

  1. sensory adaptation
  2. bottom-up processing
  3. top-down processing Correct answer.
  4. parallel processing

Explanation

Top-down processing uses prior knowledge, expectations, and context to interpret ambiguous sensory input. Knowing the diagnosis supplies a schema that constrains which words are likely. Bottom-up processing would rely on the letter shapes alone.

Question 9Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A radiologist is told to be extremely cautious about missing any tumor. According to signal detection theory, she will most likely:

  1. adopt a conservative criterion, lowering false alarms and hits
  2. show reduced sensitivity because caution impairs discrimination
  3. show improved sensitivity with no change in response bias
  4. adopt a liberal criterion, raising hits and false alarms Correct answer.

Explanation

Signal detection theory separates sensitivity from response bias. Urging caution about misses shifts the criterion toward reporting "signal present," which increases hits but also increases false alarms. Sensitivity, indexed by d-prime, is not altered by the instruction.

Question 10Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

After a few minutes in a hot bath, the water feels noticeably less hot. This change is best described as:

  1. perceptual constancy applied to temperature
  2. response bias caused by expectations
  3. an increase in the just noticeable difference
  4. sensory adaptation of warm receptors Correct answer.

Explanation

Sensory adaptation is the decreased responsiveness of receptors to an unchanging stimulus, so a constant warm input feels progressively less intense. The receptors have not stopped firing entirely, but their firing rate has declined.

Question 11Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

When a person fixates on an object held close to the face, each eye receives a slightly different image of it. This depth cue is:

  1. retinal disparity Correct answer.
  2. convergence
  3. relative size
  4. motion parallax

Explanation

Retinal disparity is the difference between the images falling on the two retinas, and the brain uses its magnitude to estimate distance for nearby objects. Convergence is the inward turning of the eyes, a separate binocular cue that relies on muscle feedback rather than image differences.

Question 12Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

In a photograph, a distant tree appears smaller than a nearby tree of the same species. Depth perceived from this difference relies on:

  1. linear perspective
  2. interposition
  3. relative size Correct answer.
  4. texture gradient

Explanation

Relative size uses the comparison of retinal image sizes for objects assumed to be of similar actual size; the smaller image is inferred to be farther away. Linear perspective, interposition, and texture gradient use different stimulus information.

Question 13Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Place theory accounts best for pitch perception of:

  1. sounds below 20 Hz
  2. high-frequency sounds Correct answer.
  3. complex tones only
  4. low-frequency sounds

Explanation

Place theory holds that pitch is coded by the location along the basilar membrane where vibration is greatest, which works well for higher frequencies. Low frequencies are better explained by frequency, or temporal, theory because neurons can fire in phase with the stimulus.

Question 14Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A soldier wounded in battle reports little pain until reaching the aid station. Gate-control theory best explains this through:

  1. destruction of nociceptors during intense stress
  2. large-fiber and descending input closing the gate Correct answer.
  3. release of substance P at the spinal cord
  4. loss of function in the somatosensory cortex during stress

Explanation

Gate-control theory proposes that pain signals in small fibers can be blocked by activity in large fibers and by descending signals from the brain, effectively closing a spinal "gate." Intense arousal and the demands of combat can engage these blocking mechanisms, reducing perceived pain.

Question 15Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

At a crowded party, a woman can follow one conversation while ignoring others yet immediately notices her own name spoken across the room. This is:

  1. the cocktail party effect Correct answer.
  2. change blindness
  3. inattentional blindness
  4. divided attention

Explanation

The cocktail party effect is the ability to focus selective attention on one stream of speech while still detecting personally relevant information, such as one's own name, in unattended streams. It demonstrates that unattended input is processed at some level even when not consciously followed.

Question 16Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Viewers counting basketball passes often fail to notice a person in a gorilla suit walking through the scene. This demonstrates:

  1. perceptual set
  2. inattentional blindness Correct answer.
  3. sensory adaptation
  4. change blindness

Explanation

Inattentional blindness occurs when an unexpected object goes unnoticed because attention is engaged by another task. The gorilla is visible in the display but is not perceived when observers are focused on counting passes.

Question 17Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Hubel and Wiesel found that many neurons in the primary visual cortex respond most strongly to:

  1. overall brightness of the visual scene
  2. faces of familiar people
  3. spots of light anywhere in the visual field
  4. bars of light at particular orientations Correct answer.

Explanation

Simple and complex cortical cells respond selectively to edges and bars with particular orientations, showing that visual cortex extracts features rather than registering raw light spots. Spot detection is characteristic of retinal ganglion cells and lateral geniculate neurons.

Question 18Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A person walking away down a street still appears roughly the same height even though the retinal image shrinks. This is:

  1. brightness constancy
  2. size constancy Correct answer.
  3. perceptual set
  4. shape constancy

Explanation

Size constancy is the perception of an object's actual size as stable despite changes in the size of the retinal image with distance. The visual system combines image size with distance cues to arrive at a stable estimate.

Question 19Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Hearing the syllable "ba" while watching a speaker's lips form "ga" often leads listeners to perceive "da." This best illustrates:

  1. sensory adaptation in the auditory system
  2. frequency theory of pitch
  3. multisensory integration in speech perception Correct answer.
  4. the phi phenomenon

Explanation

The effect shows that auditory and visual speech information are combined into a single percept, a hallmark of multisensory integration. Neither modality alone determines the experience; the brain fuses conflicting cues into a compromise percept.

Question 20Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Most of the ability to tell cinnamon from nutmeg while eating depends primarily on:

  1. texture receptors in the mouth
  2. olfactory receptors in the nasal cavity Correct answer.
  3. trigeminal pain receptors
  4. taste receptor cells on the tongue

Explanation

Taste buds detect only basic qualities such as sweet, sour, salty, bitter, and umami; the distinctive identity of a spice comes largely from retronasal olfaction as molecules travel from the mouth to the nasal cavity. Flavor is therefore a combined taste-odor percept, and smell loss markedly flattens flavor perception.

Question 21Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

People raised in environments containing few right angles are less susceptible to the Müller-Lyer illusion than people raised in urban settings. This finding best supports:

  1. cultural experience shaping perceptual interpretation Correct answer.
  2. that depth cues are unavailable in such environments
  3. a strong genetic basis for visual illusions
  4. the idea that illusions arise from retinal convergence

Explanation

Cross-cultural differences in illusion susceptibility suggest that perceptual habits learned from the visual environment shape how ambiguous figures are interpreted. People accustomed to carpentered corners appear to read the arrow ends as depth cues, amplifying the illusion.

Question 22Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Two observers make their judgments on the same detection task and achieve identical d-prime values, yet one reports many more hits and false alarms than the other. Their difference is best described as a difference in:

  1. sensitivity
  2. absolute threshold
  3. response criterion Correct answer.
  4. sensory adaptation

Explanation

d-prime indexes sensitivity, the separation between the noise and signal-plus-noise distributions. When d-prime is equal but hit and false-alarm rates differ, the observers have placed their decision criterion at different points along the same underlying distributions.

Question 23Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Participants first view a series of animal pictures and then see an ambiguous figure; they tend to report seeing an animal. This illustrates:

  1. perceptual set Correct answer.
  2. retinal disparity
  3. bottom-up processing
  4. the phi phenomenon

Explanation

A perceptual set is a temporary readiness to perceive a stimulus in a particular way, induced by prior context or expectation. The preceding animal pictures bias interpretation of the ambiguous figure toward an animal interpretation.

Question 24Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A dancer can touch her nose with her eyes closed because of information from:

  1. the vestibular apparatus alone, without other input
  2. cutaneous touch receptors alone
  3. the semicircular canals
  4. proprioceptors in muscles and joints Correct answer.

Explanation

Proprioceptors in muscles, tendons, and joints signal the position and movement of body parts, allowing accurate guidance of the arm without vision. The vestibular system contributes to balance and head orientation but does not by itself specify limb position.

Question 25Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

The visual system analyzes color, form, and motion in separate pathways, yet observers experience a single unified object. This puzzle is known as:

  1. the phi phenomenon
  2. the binding problem Correct answer.
  3. sensory conflict
  4. the Young-Helmholtz problem

Explanation

The binding problem refers to the question of how features processed in distributed, specialized pathways are integrated into a coherent percept of a single object. Proposed solutions include attention-driven integration and synchronized neural firing.

Question 26Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A person can just detect a 1-ounce increase when holding a 10-ounce weight, but needs a 2-ounce increase to notice a change when holding a 20-ounce weight. This pattern illustrates:

  1. Signal detection theory
  2. Fechner's law
  3. Stevens' power law
  4. Weber's law Correct answer.

Explanation

Weber's law states that the just-noticeable difference is a constant proportion of the original stimulus intensity rather than a fixed amount. Doubling the starting weight therefore doubles the increment needed for detection.

Question 27Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

The finding that people with normal color vision can match any color by adjusting the intensity of three primary lights is most consistent with:

  1. Opponent-process theory
  2. Place theory
  3. Frequency theory
  4. Trichromatic theory Correct answer.

Explanation

Trichromatic theory proposes three cone types with different spectral sensitivities whose combined activity produces color experience. Color matching with three primaries supports this idea.

Question 28Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

In a display, six dots are arranged in two tight clusters of three, with a wide gap between clusters. Observers tend to perceive two groups of three rather than six separate dots. This illustrates the Gestalt principle of:

  1. continuity
  2. similarity
  3. proximity Correct answer.
  4. closure

Explanation

The principle of proximity states that objects near one another tend to be grouped together. The wide gap separates the clusters into two perceived groups.

Question 29Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

The primary role of the ossicles in hearing is to:

  1. Amplify only high-frequency sounds
  2. Convert sound waves into electrical signals
  3. Detect the direction of a sound source
  4. Transmit vibrations to the oval window Correct answer.

Explanation

The malleus, incus, and stapes transmit vibrations from the tympanic membrane to the oval window and help match the impedance of air to the fluid-filled cochlea. Transduction into neural signals occurs later, in the hair cells.

Question 30Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Unlike visual and auditory signals, olfactory information reaches the cerebral cortex:

  1. After crossing at the optic chiasm
  2. Through the cochlear nucleus
  3. Without first relaying through the thalamus Correct answer.
  4. Only after passing through the lateral geniculate nucleus

Explanation

Olfactory receptor neurons project to the olfactory bulb and then directly to piriform cortex and related regions, bypassing the thalamic relay that most other sensory systems use.

Question 31Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

The taste quality known as umami is best described as:

  1. A sour taste produced by acids
  2. A bitter taste that warns of toxins
  3. A salty taste produced by sodium ions
  4. A savory taste from glutamate Correct answer.

Explanation

Umami is a savory taste triggered by glutamate and certain nucleotides. It is considered a basic taste alongside sweet, salty, sour, and bitter.

Question 32Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Which photoreceptors are most responsible for vision in very dim light?

  1. Ganglion cells
  2. Rods Correct answer.
  3. Cones
  4. Bipolar cells

Explanation

Rods are highly sensitive photoreceptors that support scotopic vision in dim light. Cones require brighter light but provide higher acuity and color vision.

Question 33Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Information about the position and movement of body parts, derived from receptors in muscles, tendons, and joints, is known as:

  1. Kinesthesis Correct answer.
  2. Vestibular sense
  3. Nociception
  4. Thermoception

Explanation

Kinesthesis is the sense of body position and movement based on receptors in muscles, tendons, and joints. The vestibular sense concerns balance and spatial orientation.

Question 34Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

After staring at a green square for 30 seconds and then looking at a blank white wall, a person sees a red afterimage. This is best explained by:

  1. Opponent-process theory Correct answer.
  2. Trichromatic color theory
  3. Gestalt law of closure
  4. Place theory of pitch

Explanation

Opponent-process theory posits paired color channels such as red-green. Prolonged green stimulation fatigues the green response, so the opposing red response dominates when the stimulus is removed.

Question 35Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

The gradual improvement in sensitivity to dim light after entering a dark room is due primarily to:

  1. Adaptation of hair cells in the cochlea
  2. Increased firing of cones within seconds
  3. Regeneration of rhodopsin in rods Correct answer.
  4. Opening of the pupil alone

Explanation

Dark adaptation occurs as rod photopigment, rhodopsin, regenerates over several minutes, increasing sensitivity to dim light. Pupil dilation contributes only a small, rapid part of the change.

Question 36Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A tone of 2,000 Hz cannot be encoded by a single auditory nerve fiber firing once per cycle, because neurons cannot fire that rapidly. The volley principle resolves this by proposing that:

  1. The ossicles amplify high-frequency sounds more than low-frequency sounds
  2. The frequency of a sound is perceived relative to a standard reference tone
  3. Groups of auditory nerve fibers fire in alternating phases Correct answer.
  4. Different regions of the basilar membrane respond to different frequencies

Explanation

The volley principle states that multiple auditory nerve fibers can take turns firing in alternating phases, collectively representing frequencies above the limit of any single neuron. This extends frequency coding beyond the refractory period of one fiber.

Question 37Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

The binaural cue based on the slight difference in the time at which a sound reaches the two ears is called:

  1. Place coding
  2. Interaural time difference Correct answer.
  3. Interaural level difference
  4. Phase locking

Explanation

Interaural time difference is the slight difference in arrival time of a sound at the two ears and is especially useful for localizing low-frequency sounds. Interaural level difference relies on intensity differences.

Question 38Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

The utricle and saccule contribute to balance primarily by detecting:

  1. Linear acceleration Correct answer.
  2. Rotational acceleration
  3. Sound frequency
  4. Muscle stretch

Explanation

The utricle and saccule contain otoliths that detect gravity and linear acceleration, including head tilt. Rotational acceleration is detected mainly by the semicircular canals.

Question 39Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

When a driver looks out the side window, roadside signs whip past while distant mountains seem to move slowly. This depth cue is:

  1. Linear perspective
  2. Motion parallax Correct answer.
  3. Convergence
  4. Texture gradient

Explanation

Motion parallax is the depth cue in which near objects move faster across the retina than far objects when the observer moves. The relative speed of retinal motion signals distance.

Question 40Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A field of flowers appears as distinct individual blooms in the foreground but as a smooth continuous color in the distance. This depth cue is:

  1. Interposition
  2. Retinal disparity
  3. Relative height
  4. Texture gradient Correct answer.

Explanation

Texture gradient is the gradual change from coarse, detailed texture in nearby objects to fine, indistinct texture in distant objects. This gradient provides information about distance.

Question 41Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Two stationary lights flashed in rapid succession at slightly different positions appear as one light moving back and forth. This is called the:

  1. Moon illusion
  2. Autokinetic effect
  3. Waterfall illusion
  4. Phi phenomenon Correct answer.

Explanation

The phi phenomenon is the perception of apparent motion between two stationary stimuli presented in rapid alternation. It underlies many motion-picture effects.

Question 42Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Reading a word by first identifying each letter and then combining the letters into a whole word relies primarily on:

  1. Bottom-up processing Correct answer.
  2. Perceptual constancy
  3. Perceptual set
  4. Top-down processing

Explanation

Bottom-up processing begins with sensory features and builds toward a whole percept. Identifying letters first and then assembling them into a word follows this data-driven sequence.

Question 43Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A driver talking on a hands-free phone is slower to brake when a car ahead stops suddenly. This best illustrates:

  1. Signal detection sensitivity
  2. Divided attention costs Correct answer.
  3. Sensory adaptation
  4. Perceptual constancy

Explanation

Divided attention occurs when mental resources are split between tasks, reducing performance on one or both. The phone conversation competes with driving for attentional resources.

Question 44Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A person fails to notice that the actor playing a character has been replaced between two brief film cuts. This is an example of:

  1. Inattentional blindness
  2. Choice blindness
  3. Sensory habituation
  4. Change blindness Correct answer.

Explanation

Change blindness is the failure to detect a change in a scene, often when the change occurs during a brief interruption. The replacement of the actor is a change that goes unnoticed.

Question 45Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A person consistently experiences the number 7 as green and the word 'Tuesday' as tasting of cinnamon. This condition is called:

  1. Agnosia
  2. Prosopagnosia
  3. Anosmia
  4. Synesthesia Correct answer.

Explanation

Synesthesia is a condition in which stimulation in one sensory or cognitive channel automatically evokes an experience in another channel. The cross-modal pairings described are characteristic of synesthesia.

Question 46Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A person puts on a wristwatch and quickly stops feeling it against the skin. Which receptor property best accounts for this rapid loss of awareness?

  1. Receptive fields enlarge with sustained stimulation
  2. Tonic receptors maintain firing throughout the stimulus
  3. Transduction requires conscious attention
  4. Phasic receptors adapt rapidly to a sustained stimulus Correct answer.

Explanation

Phasic receptors are rapidly adapting and respond mainly to changes in stimulation, so sustained pressure becomes less noticeable. Tonic receptors, in contrast, continue firing as long as the stimulus persists.

Question 47Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A researcher finds that two points can be distinguished on the fingertip when they are 2 mm apart, but on the back they must be 40 mm apart. This difference reflects variation in:

  1. Two-point threshold Correct answer.
  2. Receptor adaptation rates
  3. Vestibular sensitivity
  4. Pain tolerance

Explanation

The two-point threshold is the minimum distance at which two points of stimulation are perceived as separate. It is smaller where receptor density and cortical representation are greater, such as the fingertips.

Question 48Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Patients given a placebo for pain often report reduced pain, and this effect is partly reversed by naloxone. This suggests placebo analgesia involves:

  1. Blockade of endogenous opioid receptors
  2. Increased activity of A-delta fibers
  3. Release of endogenous opioids Correct answer.
  4. Damage to the somatosensory cortex

Explanation

Naloxone is an opioid receptor antagonist, so its reversal of placebo analgesia implies that placebo effects involve endogenous opioid release. This is a form of top-down pain modulation.

Question 49Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

A door swinging open appears increasingly trapezoidal on the retina, yet the observer continues to perceive it as rectangular. This demonstrates:

  1. Shape constancy Correct answer.
  2. Color constancy
  3. Brightness constancy
  4. Size constancy

Explanation

Shape constancy is the tendency to perceive an object's shape as stable despite changes in the retinal image caused by viewing angle. The door is still perceived as rectangular even as its retinal projection changes.

Question 50Foundational Concept 6: biological, psychological, and sociocultural factors that influence how we sense and perceive the world and respond to it

Visual acuity is highest when an image falls on the fovea because the fovea:

  1. Lacks any photoreceptors
  2. Contains mostly rods
  3. Is the point where the optic nerve leaves the eye
  4. Contains a high density of cones Correct answer.

Explanation

The fovea is densely packed with cones and has minimal convergence onto ganglion cells, allowing high spatial resolution. Rods are sparse or absent in the fovea.