Intro to sensation Flashcards
sensation
To represent the world, we must detect physical energy (stimulus) from the environment and convert it into neural signals,
perception
When we select, organize, and interpret our sensations, the process is called perception.
Bottom-up Processing
Analysis of the stimulus begins with the sense receptors
and works up to the level of the brain and mind.
Top-down Processing
Information processing guided by high-level mental processes as we construct perceptions drawing on our experience and expectations.
Absolute Threshold
Minimum stimulation needed to detect a particular stimulus 50% of the time.
Difference Threshold
The minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND).
Weber’s Law
The size of the JND is proportional to the intensity of the
stimulus
× if the stimulus intensity is high, the JND will be large (or it will take a bigger change to notice the difference)
× if the stimulus intensity is low, the JND will be smaller (or it will take less of an change to notice the difference)
Subliminal Threshold
When stimuli are below one’s absolute threshold for conscious awareness.
Signal Detection Theory
Simply put, it states that our thresholds are not absolute – they change.
Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). Assumes that there is no single absolute threshold and detection depends on: Experience, Expectations, Motivation, Level of Fatigue
Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
Like when wearing a band-aid, jewelry, glasses, or getting into a cold pool.
Gestalt Psychology
helps us organize information into meaningful
wholes…
but remember…the “whole is different from the sum
of it’s parts”
Figure-ground
Organization of the visual field into objects (figures) that stand out from their surroundings (ground).
Gestalt Grouping
The whole is more important then the parts .
Depth Perception
Depth perception enables us to judge distances. Gibson and Walk
(1960) suggested that human infants (crawling age) have depth
perception. Even new born animals show depth perception.
Monocular Cues - Interposition
Objects that occlude (block) other objects tend to be perceived as closer.
Monocular Cues
Linear Perspective:
Parallel lines like rail road tracks, appear to converge with distance. The more the lines converge, the greater their
perceived distance.
Monocular Cues
Relative Size:
If two objects are similar in size, we perceive one that casts a smaller retinal image as farther away.
Monocular Cues
Texture Gradient:
Indistinct (fine) texture signals increasing
distance.
Binocular Cues Convergence:
When two eyes move inward (towards the nose) to see near objects, and outward (away from the nose) to see far away objects…object is perceived as closer the more eyes turn inward
Binocular Cues
Retinal disparity:
Images from the
two eyes differ…the greater the
difference between the two objects,
the closer the object
