Glossary
Absolute Threshold
The minimum stimulation needed to detect a particular stimulus 50% of the time.
Example:
Imagine trying to hear the faint whisper of a friend from across a quiet classroom; the quietest sound you can detect half the time is your absolute threshold for hearing.
Binocular Cues
Depth cues that depend on the use of two eyes, providing information about distance and depth.
Example:
When you hold your finger close to your face and alternate closing each eye, the apparent shift in your finger's position is due to binocular cues.
Bottom-up Processing
Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information.
Example:
Learning a new language by first recognizing individual sounds and letters, then combining them into words, is an example of bottom-up processing.
Change Blindness
Failing to notice changes in the environment, especially when those changes occur during a brief visual disruption or when attention is focused elsewhere.
Example:
If a person you're talking to briefly ducks behind a counter and is replaced by a different person, you might not notice the switch, demonstrating change blindness.
Cocktail Party Effect
Your ability to attend to only one voice among many, while still being able to detect personally significant information, like your name, from unattended voices.
Example:
At a loud party, you can focus on a conversation with one friend, but if someone across the room mentions your name, you instantly shift your attention, illustrating the cocktail party effect.
Context Effects
How the context in which a stimulus is perceived influences our perception of it.
Example:
Hearing the word 'bear' might make you think of a large animal in a forest, but if you see it written as 'bare' in the context of 'bare feet,' your interpretation changes due to context effects.
Difference Threshold (Just Noticeable Difference - JND)
The minimum difference between two stimuli required for a person to detect that difference 50% of the time.
Example:
If you're holding a 10-pound weight, the difference threshold is the smallest amount of weight you'd need to add or remove for you to notice a change.
Feature Detectors
Specialized nerve cells in the brain that respond to specific features of a visual stimulus, such as shape, angle, or movement.
Example:
When you see a baseball flying towards you, specific feature detectors in your brain activate to process its round shape and rapid motion.
Figure-Ground Relationship
The Gestalt principle of organization that states we spontaneously organize visual information into objects (the figure) that stand out from their surroundings (the ground).
Example:
When looking at a black vase on a white background, you might either see the vase (figure) or two white faces in profile (figure) against a black background (ground), illustrating the figure-ground relationship.
Inattentional Blindness
Failing to see visible objects when our attention is directed elsewhere.
Example:
While counting the number of passes in a basketball game, you might completely miss a person in a gorilla suit walking across the court, a classic example of inattentional blindness.
Monocular Cues
Depth cues available to either eye alone, used by the brain to judge distance.
Example:
Artists use monocular cues like linear perspective, where parallel lines appear to converge in the distance, to create the illusion of depth on a flat canvas.
Perception
The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
Example:
After light waves hit your retina (sensation), your brain interprets those patterns as a familiar face, which is an act of perception.
Perceptual Set
A mental predisposition to perceive one thing and not another, often influenced by our experiences, assumptions, and expectations.
Example:
If you're expecting to hear a scary sound while watching a horror movie, you might interpret a creaking floorboard as a monster, due to your perceptual set.
Retinal Disparity
A binocular cue for perceiving depth, referring to the slight difference between the images seen by the left and right eyes, which the brain uses to calculate distance.
Example:
When you look at a 3D movie, the glasses create two slightly different images for each eye, mimicking retinal disparity to create the illusion of depth.
Schemas
Concepts or mental frameworks that organize and interpret information, helping us make sense of the world.
Example:
Your mental schema for 'dog' includes characteristics like four legs, fur, barking, and loyalty, which helps you quickly identify new dogs.
Selective Attention
Focusing conscious awareness on a particular stimulus, while filtering out other incoming information.
Example:
When you are deeply engrossed in a video game, you might not hear your parents calling your name, demonstrating your selective attention to the game.
Sensation
The process where our sensory receptors and nervous system receive and represent stimulus energies from the environment.
Example:
When light waves hit your retina, that initial reception of energy is sensation, before your brain interprets what you are seeing.
Sensory Adaptation
Diminished sensitivity to a stimulus as a consequence of constant stimulation.
Example:
When you first jump into a cold swimming pool, it feels freezing, but after a few minutes, your body adjusts, and you experience sensory adaptation.
Signal Detection Theory
A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise), taking into account psychological factors.
Example:
A lifeguard's ability to spot a struggling swimmer in a crowded pool, influenced by their training and alertness, is explained by signal detection theory.
Subliminal
Referring to stimuli that are below one's absolute threshold for conscious awareness.
Example:
A fleeting image of a soda bottle flashed so quickly on a screen that you don't consciously see it is a subliminal stimulus.
Top-down Processing
Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.
Example:
Reading a messy handwritten note and still understanding it because your brain uses context and prior knowledge to fill in the missing letters demonstrates top-down processing.
Weber's Law
The principle stating that for a difference between two stimuli to be perceived, they must differ by a constant minimum percentage, rather than a constant amount.
Example:
If you can tell the difference between a 10-ounce and an 11-ounce soda, according to Weber's Law, you'd need a 2-ounce difference to notice a change when comparing a 20-ounce soda.