Sensation and Perception Psychology Flashcards
Ernst Weber
Published De Tactu which introduced Just Noticeable Differences in sensation.
Wertheimer
Founded Gestalt Psychology
Absolute Thresholds
The minimum of stimulus energy needed to activate a sensory system.
Limen
Another word for threshold.
i.e. subLIMINAL perception means perception below the threshold of conscious awareness.
Difference Thresholds
How different two stimuli must be in magnitude before they can be perceived to be different.
Just Noticeable Difference (JND)
The amount of change necessary to predict the difference between two stimuli.
Weber’s Law
The change in stimulus intensity needed to produce a JND divided by the stimulus intensity of the standard stimulus is constant. Sometimes referred to as Weber’s Fraction/Weber’s Constant.
Fechner’s Law
Expresses the relationship between the intensity of the sensation and the intensity of the stimulus. Generally finds that sensation increases more slowly than intensity.
Steven’s Power Law
Disproves Fechner’s law and replaces it with a new theory regarding how sensation and intensity interact.
Signal Detection Theory
Suggests that there are other nonsensory factors which influence what the subject says they sense (i.e. if they’re overly cautious).
Response Bias
The tendency of subjects to respond in a particular way due to nonsensory factors.
Receiver Operating Characteristic (ROC)
Curves which researchers use to summarize a subject’s response by measuring the sensitivity characteristics of a subject receiving signals.
John A Swets
Refined the use of ROC curves.
Steps to Sensory Info Processing
Reception
Transduction
Sent to projection areas/Processed by nervous system
Transduction
The translation of physical energy into the neuro impulses or action potentials
Parts of the Eye
Cornea- clear dome window gathers and focuses light
Pupil- hole in iris which contracts in light/expands in dim
Iris- colored part of eye, controls light entering eye through pupil
Lens- behind the iris, controls the curvature of light and focuses retina
Retina- screen filled w neural elements (image detecting)
Fovea- middle of retina with only cones. Best visual acuity.
Rods v Cones
Cones = color vision, fine details. most effective in bright light, allow us to see chromatic and achromatic colors
Rods = perceive achromatic colors, most effective in dim light, low sensitivity to details, no color vision.
Connection of cells in eyes
Rods/Cones connect to bipolar neurons
Bipolar neurons connect to ganglion cells
Ganglion cells group together to become optic nerve
Ratio of ganglion to cones much smaller than to rods, which is why cones are better at details.
Optic Chiasm
place where the fibers from the nasal half of retina cross paths (but not the fibers from the temporal fibers). Leads to all info from left visual field going right hemisphere and visa versa.
Where Optic Chiasm info goes
Lateral Geniculate Nucleus (in thallamus)
Visual Cortex in Occipital Lobe
Superior Colliculus
Hubel and Wiesel
Found the neural basis for feature detection theory.
Feature Detection Theory
Suggests that certain cells in the cortex are maximally sensitive to certain features of stimuli.
Three types of cells for feature detection
Simple - respond to orientation
Complex- respond to movement
Hypercomplex- respond to shape
Illumination v Brightness
Illumination - physical/objective measurement of the amount of light on a surface
Brightness - subjective impression of the intensity of light.
Factors in how we perceive Brightness
Adaption - When you become accustomed to the environment and see better
Photopigment
When the rods have a photochemical called rhodopsin
Rohodopsin
Made up of Vitamin A derivative, called retinal, and opsin (a protein).
Bleaching
When rhodopsin absorbs light, the pigment decomposes, (splits into retinene and opsin). Once you’re in the dark, the pigments regenerate leading to you seeing better and adapting to the dark. Vitamin A is crucial in this process.
Simultaneous Brightness Contrast
Target Area of a particular luminance appears brighter if surrounded by darker stimulus. Explained by lateral inhibition.
Lateral Inhibition.
When adjacent retinal cells inhibit eachother. If one cell is excited, the neighboring cells are inhibited. This leads to simultaneous brightness contrast and helps us to sharpen the borders between light and dark areas.
Opponent-Process Theory
Developed by Hering to criticize trichromatic theory. Suggests there were 3 opposing pairs, which signal the presence of colors which signal what the eye is seeing. The pairs were: red-green, blue-yellow, and black-white.
This theory implies you can never see a color mix of opposing pairs (ie a red-green).
Later found to be incorrect in direct vision, but applies to cells in the lateral geniculate nucleus.
Young-Helmholtz Theory
AKA: the trichromatic theory. Suggests that there are three different types of color receptors (cones), which are differentially sensitive (one to red, one to blue, and one green). Proposes that all colors are produced by combining the varying stimulation of these receptors.
Found to be correct later when there were better methods to analyze this.
Afterimages
Inspired Hering’s Theory. True in multiple things (color, motion, etc). When you have prolonged/intense exposure to a stimulus, then look at something blank, you see an afterimage of the “opposite” of the original stimuli.
George Berkeley
In 1700s, listed the various cues for depth and explained how we see depth from the 2-dimensional retina. Proposed: interposition, relative size, and linear perspective.
Depth Cue: Interposition
AKA overlap. Refers to when one object covers/overlaps with another so we see object on top as being in front and closer.