Chapter 3 I Flashcards
What is “synesthesia”?
A sensory experience in on domain accompanied by a sensory experience in another.
What is “emotional synesthesia”?
Specific stimuli are constantly and involuntarily associated with emotional responses.
What is “Grapheme-colour synesthesia”?
Words, letters or digits are associated with specific colours.
What does synesthesia show about the brain?
May reflect hyper-connectivity between parts of the brain associate with different sensory experiences.
Research shows synesthesia may be genetically associated with?
Absolute/perfect pitch.
What is “sensation”?
Stimulation of sense organs. (The absorption of energy.)
What is “perception”?
The selection, organization and interpretation of the sensory input. (Turning input into something meaningful.)
What is “psychophysics”?
The study of how physical stimuli are translated into psychological experiences.
Who was a particularly important contributor to psychophysics?
Gustav Fechner (1860), worked at University of Leipzeg.
Sensation begins with a ___?
Stimulus. (Any detectable input from the environment.)
What is a “threshold”?
A dividing point between energy levels that do and do not have a detectable effect.
What is an “absolute threshold” for a specific sensory input?
The minimum amount of stimulation that an organism can detect. Define the boundaries of an organism’s sensory capabilities.
As stimulus increases, subject’s probability of responding to that stimuli ______ _______?
Gradually increases.
Through research what was discovered of the “absolute threshold”?
It was arbitrarily defined as the intensity level at which the probability of detection is 50%.
What is a “JND”?
Just Noticeable Difference. The smallest difference in the amount of stimulation that a specific sense can detect.
What is the difference between the absolute threshold and the JND?
The absolute threshold is the JND from nothing.
What does “Weber’s Law” state?
The size of the JND is a constant proportion of the size of the initial stimulus. (Weber fraction.)
What does “signal-detection” theory propose?
That the detection of stimuli involves decision processes as well as sensory processes which are both influenced by a variety of factors. (ie: Possible enemy aircraft simulation in textbook 131)
Responses will depend on the _____ you set for how sure you must feel before you react.
Criterion.
According to signal-detection theory, your performance will also depend on the level of ____?
Noise.
What is “noise”?
All of the irrelevant stimuli in the environment and neural activity they elicit. More noise = harder to pick up signal.
Signal detection theory replaces Fechner’s sharp threshold with the concept of _____?
Detectability.
What is “subliminal perception”?
The registration of sensory input without conscious awareness.
Karremans, Stroebe and Claus’ (2006) study used what to test subliminal messaging?
Lipton Iced Tea. Subliminal presentations at 23/1000 second were shown for half of the subjects. All subjects were later monitored and exposed to Lipton iced tea.
Subliminal stimulation generally produces ____? That can only be detected how and where?
Weak effects. Can only be detected under precise measurement in carefully controlled laboratory conditions.
What is “sensory adaptation” ?
A gradual decline in sensitivity due to prolonged stimulation.
Why does sensory adaptation likely exist?
To keep people tuned into the changes rather than the constants.
Light waves vary in ___ and ___.
Amplitude (height) and wavelength (distance between peaks).
Amplitude of light affects what?
The perception of brightness.
Wavelength of light affects what?
The perception of colour.
Eyes serve what 2 main purposes?
- They channel light to the neural tissue that receives it, the retina.
- They house that tissue.
Where does light enter the eye?
The cornea.
What is the significance of the “lens”?
The transparent part of the eye that focuses the light ray falling on the retina.
What is “accommodation”?
This occurs when the curvature of the lens adjusts to alter visual focus.
What happens to the lens when you focus on a close object?
Lens gets fatter and rounder to give a clear image.
Explain “nearsightedness”?
Close objects are seen clearly but distant ones often appear blurry. Due to the cornea bending light too much or the eyeball being too long.
Explain “farsightedness”?
Distant objects are seen clearly but close ones are not. Due to focus of the light from the object falling behind the retina or the eyeball being to short.
What is the coloured ring around the pupil called?
The iris.
What is the “pupil”?
The opening in the centre of the iris that helps regulate the amount of light passing through to the rear chamber of the eye.
When the pupil constricts it lets ____ light in.
Less.
When the pupil dilates it lets ____ light in.
More. (Makes image less sharp.)
Tiny eye movements that are actually brief fixations on various parts of environmental stimuli are called?
Saccades.
What is the “retina”?
The neural tissue lining the inside of the back surface of the eye. It absorbs light, process images and sends visual information to the brain.
Is the retina a part of the CNS?
Yes.
What are the receptor cells in the back of the eye called?
Rods and cones.
Which cells actually carry the visual signals through axons in the optic nerve?
Ganglion cells.
What is the “optic disk”?
A hole in the retina where the optic nerve fibers exit the eye. Blind spot occurs when an image falls on this part of the eye.
What are “cones”?
One type of receptor cell in the eye. (Outnumbered by rods). They play a key role in daylight and colour vision.
Cones provide better visual ___?
Acuity. Better sharpness and precise detail than rods.
What is the spot in the retina that only contains cones that has the best visual acuity called?
The fovea.
What are “rods”?
The other kind of specialized cell in the retina. Plays a key role in night and peripheral vision. (There are more rods than cones). They are more sensitive to dim light.
Why do we avert our vision in the dark?
The distribution of the rods. To move the image away from the fovea to a rod dominated area.
The process by which our eyes become more sensitive to light in low illumination is called?
Dark adaptation. Vice versa = light adaptation.
Do cones or rods adapt more rapidly to change in light?
Cones adapt quicker.
What is the “receptive field”?
The retinal area that, when stimulated, affects the firing of that cell. As an example, light in the center produces excitatory effects and increased firing.
Arrangements of receptive fields in the retina make visual cells particularly sensitive to what?
Contrast which is very important in recognizing the edges of objects.
Retinal cells send signals both _____ and ____?
Toward the brain and laterally toward nearby visual cells.
What is the “optic chiasm”?
The point where the optic nerves from the inside half of each eye cross over and then project to the opposite half of the brain. This ensures signals from both eyes go to both hemispheres.
What are the 2 pathways from the optic chiasm?
The main pathway which projects into the thalamus and the second on which branches to the superior colliculus in the midbrain before going through the thalamus and finally the occipital lobe.
Visual signals are processed in the ____?
LGN - lateral geniculate nucleus.
After the LGN, visual signals go where?
They are distributed to the occipital lobe that make but the primary visual cortex.
What is the function of the second pathway that first goes through the midbrain?
Coordination of the visual input with other sensory input.
What did Canadian neurophysiologist David Hubel and Swedish neurophysiologist Torsten Wiesel uncover?
Individual cells in the primary visual cortex didn’t really respond to little spots - rather they are more sensitive to lines, edges and more complicated stimuli.
What do “simple cells” respond to?
They respond best to a line of the correct width, oriented at the correct angle and located in the correct position in its receptive field.
How do “complex cells” differ than simple ones?
They too require the correct width and orientation but can respond to any position in their receptive fields.
Cells in the visual cortex seem to be ____ _____.
Highly specialized.
What is a “feature detector”?
Neurons that respond selectively to very specific features of more complex stimuli.
What are the 2 streams after initial processing in the primary visual cortex?
The ventral stream and the dorsal stream.
What is the “ventral stream”?
Processes details of what objects are actually out there, the perception of things like form and colour.
What is the “dorsal stream”?
Processes where the objects are, the perception of motion and depth.
What is “visual agnosia”?
The inability to recognize objects. Probably due to damage somewhere along the visual pathway that handles object recognition.
What is “prosopagnosia”?
The inability to recognize familiar faces, including one’s own.
Neurons in the ventral stream are involved in?
Perceiving faces and can learn from experience.
What kind of “modules” have emerged in the dorsal stream? What are they for?
Visuomotor modules, they are related to vision for action or control of goal-directed movements.
Goodale and Humphrey distinguished what 2 functions that vision serves?
Vision for perception and vision for action.
Who was patient DF?
Brain trauma due to carbon monoxide fumes. She could see full detail of objects but could no longer identify them. (Agnosia.)
What colour has the longest wavelength?
Red.
Shortest wavelength colour?
Violet.
What are the 2 dimensions of colour?
Hue (the colour itself ie: blue), brightness and saturation (purity).
What is “subtractive colour mixing”?
Works by removing some wavelengths of light, leaving less light than was originally there. Paints yield subtractive mixing because pigments absorb most wavelengths.
What is “additive colour mixing”?
Works by superimposing lights, putting more light in the mixture than exists in any one light by itself. (Example: Shining coloured spotlights on a white table.)
Who came up with the “trichromatic theory” of colour?
Thomas Young and Hermann von Helmholtz.
What does the “trichromatic theory” state?
It says that the human eye has 3 types of receptors with differing sensitivities to different light wavelengths. These were associated with the colours red, green and blue.
Why is the term “colour-blindness” not correct?
Most people are not truly “blind” but are dichromatic. They make do with only 2 colour channels.
What is an “afterimage”?
A visual image that persists after a stimulus is removed. The colour of the afterimage will be the complimentary colour of the one originally stared at. (ie: orange and blue)
Who proposed the “opponent process theory”?
Ewald Hering.
What does the “opponent process theory” state?
That colour perception depends on receptors that make antagonistic responses to 3 pairs of colours.
What were the pairs of “opponent” colours?
Red vs. green, yellow vs. blue and black vs. white
What names are required to name colours?
Red, blue, green and YELLOW.
What theory, opponent process or trichromatic theory, was correct?
It is clear that both are needed to explain colour vision. Although there are 3 types of cones that are most sensitive to either blue, green or red, there are also cells that respond in OPPOSITE ways to the colour opponents.
Where did researchers discover cells that use the opponent process?
Retina (ganglion cells), LGN and visual cortex.
