Glossary
Absolute Threshold
The minimum stimulation needed to detect a particular stimulus 50 percent of the time.
Example:
The faintest whisper you can hear in a quiet room represents your absolute threshold for sound.
Body Position Senses
Senses that provide information about the position and movement of our body.
Example:
The ability to walk without constantly looking at your feet relies on your body position senses.
Bottom-Up Processing
Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information.
Example:
As you learn to read, you first process individual letters and then combine them to form words, which is an example of bottom-up processing.
Chemical Senses
Senses that respond to chemical substances in the environment.
Example:
Taste and smell are classified as chemical senses because they detect molecules.
Closure (Gestalt Principle)
A Gestalt grouping principle stating that we tend to fill in gaps to create a complete, whole object.
Example:
You can recognize a familiar logo even if parts of it are missing, as your brain applies the principle of closure.
Cochlea
A coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses.
Example:
The vibrations from a musical note are converted into neural signals within the cochlea.
Cones
Photoreceptors in the retina that are concentrated near the center of the retina and function in daylight or in well-lit conditions, detecting fine detail and giving rise to color sensations.
Example:
To appreciate the vibrant colors of a rainbow, your cones are actively engaged.
Continuity (Gestalt Principle)
A Gestalt grouping principle stating that we perceive smooth, continuous patterns rather than discontinuous ones.
Example:
Even if a tree branch partially obscures a road, you still perceive the road as a single, unbroken path because of continuity.
Difference Threshold (Just Noticeable Difference - JND)
The minimum difference between two stimuli required for detection 50 percent of the time.
Example:
The smallest amount you can increase the volume of your music before you notice a change is the difference threshold.
Energy Senses
Senses that respond to physical energy from the environment, such as light waves, sound waves, and pressure.
Example:
Vision, hearing, and touch are considered energy senses because they detect physical forms of energy.
Figure-Ground Relationship
The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).
Example:
In a crowded room, focusing on a friend's face while blurring out the people behind them demonstrates the figure-ground relationship.
Gestalt
A German word meaning 'form' or 'whole,' referring to the idea that we tend to organize our sensations into a meaningful whole.
Example:
When you look at a painting, you see the entire scene rather than just individual brushstrokes, illustrating the concept of Gestalt.
Gustation
The sense of taste, which involves receptors on the tongue that detect sweet, sour, salty, bitter, and umami flavors.
Example:
Enjoying the complex flavors of a gourmet meal is an experience of gustation.
Kinesthetic Sense
The sense of the position and movement of individual body parts, provided by receptors in muscles, tendons, and joints.
Example:
Knowing where your hands are in relation to the keyboard without looking is an example of your kinesthetic sense at work.
Necker Cube
An optical illusion that demonstrates how our minds actively construct perceptions, allowing us to perceive a 3D cube from a 2D drawing in two different orientations.
Example:
Staring at the Necker Cube and seeing it flip its orientation highlights how our brain interprets ambiguous visual information.
Olfaction
The sense of smell, which involves receptors in the nasal cavity that detect airborne chemical molecules.
Example:
The comforting aroma of freshly baked cookies is detected through olfaction.
Perception
The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
Example:
After seeing lines and colors, your brain interprets them as a familiar face, demonstrating perception.
Proximity (Gestalt Principle)
A Gestalt grouping principle stating that we tend to group nearby objects together.
Example:
When you see a cluster of stars in the night sky, you perceive them as a constellation rather than individual stars due to proximity.
Rods
Photoreceptors in the retina that detect black, white, and gray, and are necessary for peripheral and twilight vision when cones don't respond.
Example:
When walking in a dimly lit room, your rods are primarily responsible for helping you see shapes and outlines.
Sensation
The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.
Example:
When you touch a hot stove, the immediate feeling of heat and pain is a result of sensation.
Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
Example:
After a few minutes, you no longer notice the faint smell of your new perfume due to sensory adaptation.
Sensory Habituation
A cognitive process where the perception of a sensation decreases because you are no longer actively focusing on it.
Example:
Living near a train track, you eventually stop noticing the sound of passing trains unless you consciously pay attention, which is sensory habituation.
Sensory Transduction
The process by which our sensory systems convert stimulus energy into neural impulses that our brain can understand.
Example:
When light hits your eye, the photoreceptors perform sensory transduction by converting light energy into electrical signals for the brain.
Signal Detection Theory
A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise), depending partly on experience, expectations, motivation, and alertness.
Example:
A radiologist's ability to spot a faint tumor on an X-ray, influenced by their training and the urgency of the situation, is explained by signal detection theory.
Subliminal Stimuli
Stimuli that are below one's absolute threshold for conscious awareness.
Example:
A very brief flash of an image on a screen that you don't consciously notice is an example of 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:
You can easily read a text message even if some letters are missing because your brain uses context and prior knowledge, illustrating top-down processing.
Vestibular Sense
The sense of body movement and position, including the sense of balance, located in the inner ear's semicircular canals.
Example:
Maintaining your balance while riding a bicycle relies heavily on your vestibular sense.
Weber's Law
The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount).
Example:
If you can detect a 1-pound difference when holding a 10-pound weight, you'd need a 10-pound difference to notice a change when holding a 100-pound weight, illustrating Weber's Law.