Chapter 4 Flashcards
simple stimulation of a sense organ
Sensation
the organization, identification, and interpretation of a sensation in order to form a mental representation
Perception
when many sensors in the body convert physical signals from the environment into encoded neural signals sent to the CNS
Transduction
methods that measure the strength of a stimulus and the observer’s sensitivity to that stimulus
Psychophysics
the minimal intensity needed to just barely detect a stimulus in 50% of the trials
Absolute Threshold
the minimal change in a stimulus that can be just barely detected (also known as a difference threshold).
Just Noticeable Difference (JND)
the just noticeable difference of a stimulus is a constant proportion despite variations in intensity.
Weber’s Law
the response to a stimulus depends both on a person’s sensitivity to the stimulus in the presence of noise and on a person’s decision criterion (correct responses include correct rejection and hits).
Signal Detection Theory
sensitivity to prolonged stimulation tends to decline over time as an organism adopts to current conditions
Sensory Adaptation
the ability to see fine detail
Visual Acuity
3 Properties of Light Waves
Length (color/hue)
Amplitude (brightness)
Purity (saturation/richness)
smooth outer tissue of the eye
Cornea
hole in the coloured part of the eye
Pupil
coloured part of the eye; muscle that controls the size of the pupil
Iris
layer of light sensitive tissue lining the back of the eyeball
Retina
the process which the eye maintains a clear image on the retina
Accommodation
Nearsightedness is called; when the eyeball is too long; images focused in front of the retina
Myopia
Farsightedness is called; when the eyeball is too short; images focused behind the retina
Hyperopia
Two Types of Photoreceptor Cells
Cones
Rods
photoreceptor cell that detects colour, operates under normal daylight conditions, allows us to focus on details
Cones
photoreceptor cell that becomes active under low-light conditions for night vision; more sensitive than cones; only sense shades of grey
Rods
120 million of these are distributed around each retina everywhere except the fovea
Rods
6 million of these are in the retina, packed in the fovea
Cones
an area of the retina where vision is the clearest and there are no rods
Fovea
cells that collect neural signals from the rods and cones and transmit them to the outermost layer of the retina
Bipolar Cells
neurons that organize signals from rods and cones and send them to the brain
Retinal Ganglion Cells (RCGs)
a bundle of 1.5 million retinal ganglion cells that leave the eye through a hole in the retina.
Optic Nerve
a location in the visual field that produces no sensation on the retina
Blind Spot
part of the occipital lobe; also called the primary visual cortex
Area V1
the rainbow of hues and accompanying wavelengths
Visible Spectrum
Three Types of Cones
Red - long wavelength
Green - medium wavelength
Blue - short wavelength
a genetic disorder where one of the cone types is missing (or two or even three)
Colour Deficiency
staring too long at one colour, fatiguing the cones that respond to that colour
Colour Afterimage
pairs of visual neurons work in opposition (red-sensitive against green-sensitive, blue-sensitive against yellow-sensitive).
Colour-opponent System
two distinct pathways that project from the occipital cortex to visual areas in other parts of the brain
Visual Streams
a visual stream that travels across the occipital lobe into lower levels of the temporal lobes; includes brain areas representing an object’s shape and identity; a “what” pathway
Ventral Stream
a visual stream that travels up from the occipital lobe to the parietal lobes (and some of middle and upper temporal lobes); connects with brain areas identifying location and motion of an object; “where” pathway, should be called the “how” pathway.
Dorsal Stream
the inability to recognize objects by sight
Visual Form Agnosia
the brain’s capacity to perform many activities at the same time.
Parallel Processing
how the brain links features together so that we see unified objects in our visual world rather than free-floating or miscombined features.
Binding Problem
a perceptual mistake whereby the brain incorrectly combines features from multiple objects
Illusory Conjunction
focused attention is not required to detect the individual features that make up a stimulus, such as the colour, shape, size, and location of letters, but is required to bind those individual features together.
Feature-integration Theory