AP Psychology: Sensation & Perception 2 — Questions and Answers

Question 1: What is the absolute threshold in sensation?

The minimum stimulation needed to detect a stimulus 50% of the time (Correct answer)
The maximum amount of stimulation a person can tolerate
The point at which a stimulus becomes painful
The average intensity of environmental stimuli

Correct answer: The minimum stimulation needed to detect a stimulus 50% of the time

The absolute threshold is the minimum level of stimulus intensity needed for detection half the time.

The absolute threshold is defined as the minimum stimulus intensity that an observer can detect 50% of the time. Gustav Fechner established this concept in the 19th century. Examples include the faintest sound you can hear in a quiet room or the dimmest light visible in darkness. Signal detection theory later refined this concept by accounting for response bias and decision criteria, showing that detection depends on both sensitivity and the observer's willingness to report a signal.

Question 2: What is Weber's Law?

The just noticeable difference between two stimuli is a constant proportion of the original stimulus (Correct answer)
All senses have the same sensitivity threshold
Sensory adaptation occurs at a fixed rate for all stimuli
Perception is directly proportional to stimulus intensity

Correct answer: The just noticeable difference between two stimuli is a constant proportion of the original stimulus

Weber's Law states that the difference threshold (JND) is proportional to the magnitude of the original stimulus.

Weber's Law (Ernst Weber, 1834) states that the just noticeable difference (JND) between two stimuli is a constant ratio of the original stimulus. For example, if you can just notice the difference between 100g and 102g (Weber fraction = 1/50), you would need at least a 4g increase to detect a change from 200g. The Weber fraction varies by sense: it is approximately 1/333 for pitch, 1/60 for brightness, and 1/50 for weight. This law breaks down at extreme stimulus intensities.

Question 3: How does the trichromatic theory explain color vision?

Three types of cone receptors (red, green, blue) combine to produce all color perceptions (Correct answer)
Color is perceived by a single type of photoreceptor
Color vision depends on rod cells in the retina
The brain processes all colors equally without specialized receptors

Correct answer: Three types of cone receptors (red, green, blue) combine to produce all color perceptions

The trichromatic (Young-Helmholtz) theory proposes that color perception arises from three types of cones sensitive to different wavelengths.

The trichromatic theory (Young-Helmholtz theory) proposes that the retina contains three types of cone photoreceptors, each maximally sensitive to different wavelengths: short (blue, ~420nm), medium (green, ~530nm), and long (red, ~560nm). All perceived colors result from the combined activity of these three cone types. This theory explains color mixing and certain types of color blindness (e.g., red-green deficiency from missing M or L cones) but does not fully explain afterimages, which are better explained by opponent-process theory.

Question 4: What are Gestalt principles of perception?

Rules describing how the brain organizes sensory information into meaningful patterns (Correct answer)
Mathematical formulas for calculating stimulus intensity
Techniques for improving visual acuity
Methods for testing hearing sensitivity

Correct answer: Rules describing how the brain organizes sensory information into meaningful patterns

Gestalt principles describe how we naturally group and organize visual elements into coherent wholes rather than perceiving isolated parts.

Gestalt psychology (early 20th century, Wertheimer, Koffka, Kohler) established principles describing how the brain organizes visual input. Key principles include: proximity (nearby elements are grouped), similarity (similar elements are grouped), closure (incomplete figures are perceived as complete), continuity (smooth continuous patterns are preferred), figure-ground (objects are separated from backgrounds), and common fate (elements moving together are grouped). These principles demonstrate that perception is an active, constructive process.

Question 5: What is sensory adaptation?

Diminished sensitivity to an unchanging stimulus over time (Correct answer)
Increased sensitivity to repeated stimuli
The ability to detect very faint stimuli
The brain's preference for novel stimuli

Correct answer: Diminished sensitivity to an unchanging stimulus over time

Sensory adaptation is the tendency for sensory receptors to become less responsive to constant, unchanging stimulation.

Sensory adaptation is the decreased responsiveness of sensory receptors to constant stimulation. For example, you stop noticing the feel of clothes on your skin, background noise in a room, or an odor after prolonged exposure. This occurs because receptors reduce their firing rate for unchanging stimuli, freeing attention for novel, potentially important changes in the environment. Vision adapts through pupil adjustment and photochemical changes in rods and cones. Pain and temperature sensations also adapt, though complete adaptation to intense pain does not occur.

Question 6: What is the difference between monocular and binocular depth cues?

Monocular cues require one eye; binocular cues require both eyes working together (Correct answer)
Monocular cues are more accurate than binocular cues
Binocular cues work only at long distances
There is no functional difference between them

Correct answer: Monocular cues require one eye; binocular cues require both eyes working together

Monocular depth cues can be perceived with one eye, while binocular cues require input from both eyes to judge depth.

Depth perception uses two types of cues. Binocular cues require both eyes: retinal disparity (slightly different images from each eye) and convergence (the inward turning of eyes for near objects). Monocular cues work with one eye and include relative size, interposition (overlap), linear perspective, texture gradient, aerial perspective (haze), motion parallax, and light and shadow. Binocular cues are most effective at close distances (under ~25 feet), while monocular cues dominate at greater distances.

AP Psychology: Sensation & Perception 2

What is the absolute threshold in sensation?