Exam #2 Flashcards
abolute threshold
the minimum intensity of the stimulation that must occur before you experience a sensation (ex. How loudly would someone in the next room need to whisper for you to hear it).
difference threshold
the smallest difference between two stimuli that you can notice (if your friend is watching a show while you are reading and then a commercial comes on, you might look up to see if something has changed).
- Weber’s law
Weber’s law
the difference between two stimuli is based on a proportion of the original stimulus rather than on a fixed amount of difference → if you pick up a package that weighs one pound and a package that weighs 10 pounds you can easily spot the difference. But if you pick up a package that weighs 5 pounds and a package that weighs 5.1 pounds, you may not be able to tell as easily).
signal detection theory
States that detecting a stimulus is not an objective process, but a subjective decision with two components:
Sensitivity to the stimulus in the presence of noise (stimuli (moods, emotions, memory) and other external stimuli (the sound of the air conditioner)).
The criteria used to make the judgment from the ambiguous information.
signal detection theory attributes
If the signal is presented and the participant detects it, it becomes a HIT
If the participant fails to detect the signal, the outcome is a MISS
If the participant reports there was a signal that was not presented it is a FALSE ALARM
If the signal is not presented and the participant does not detect it, it is a CORRECT REJECTION
response bias
the tendency to report or not report detecting the signal in an ambiguous trial
sensory adaptation
Our sensory systems are tuned to detect changes in our surroundings. It is important for us to be able to detect such changes because they might require responses. It is a decrease in sensitivity to a constant level of stimulation.
McGurk effect
an auditory illusion in which auditory and visual cues provide conflicting information.
A typical experiment of this illusion is participants hearing the sound “BA” repeatedly. This is presented along with seeing a person’s mouth pronouncing “BA” in some conditions, or “VA” or “DA” in other conditions. Although the audio signal is consistently “BA”, what the participant hears will vary depending on the condition.
synesthesia
the experience of unusual combinations of sensations.
Ramachandran conducted experiments on synesthesia. He hypothesized that Because the brain area involved in seeing colors is near the brain area involved in understanding numbers, he theorized that in people with color/number synesthesia, these two brain areas are somehow connected.
James Enns
suggests that very little of what we call seeing takes place in the eyes, but rather, what we see results from constructive processes that occur throughout much of the brain to produce a visual experience.
Even if one’s eyes are completely functional, damage to one’s visual cortex will impair vision.
Process that takes place in the eye
Light passes through the cornea (the thick transparent outer layer)
The cornea focuses the light which then enters the lens
More light is focused at the cornea than at the lens, but the lens is adjustable whereas the cornea is not.
Light is bent further inward and focused to form an image on the retina (the thin inner surface of the back of the eyeball)
The retina contains sensory receptors that transduce light into neural signals (if you shine a light in someone’s eyes so that you can see the person’s retina, you are looking at the only part of the central nervous system that is visible from outside of the body).
the pupil
a small opening in the front of the lens.
By contracting (closing) or dilating (opening), the pupil can determine how much light enters into the eye. The pupil can dilate to dim a light but can also dilate when we see a beautiful painting or a cute baby.
The iris is a circular muscle that determines the eye’s color and controls the pupil’s size.
Behind the iris, muscles change the shape of the lens. They flatten the lens to focus on distant objects and thicken the lens to focus on closer objects. This describes the process of accommodation.
Essentially the lens and cornea work together to collect and focus light rays reflected from an object.
retina receptor cells
Rods
Extremely low levels of light
Responsible for night vision
Do not support color vision
Poor at fine detail
**This explains why objects in the dark can appear gray and why it is hard to read without sufficient light.
Cones
Less sensitive to low levels of light
Responsible for vision under brighter conditions
Help to see color
Help to see detail
Near the retinas center, cones are densely packed INSIDE a small region called the fovea. They become increasingly scarce the closer they are to the outside educe.
Rods are concentrated at the retina’s edges, NONE are in the fovea.
transmission from the eye to the brain
Begins with the generation of electrical signals by the sensory receptors in the retina. These receptors contain photopigments, which are protein molecules that become unstable and split apart when exposed to light.
This decomposition alters the membrane potentials in downstream neurons.
Immediately after light is transduced by the rods and cones, other cells in the middle layer of the retina perform a series of sophisticated computations. The outputs from these cells converge on the retinal ganglion cells (the first neurons in the visual pathway with axons → these are the first neurons to generate action potentials in the process of seeing).
Ganglion cells send their signals along their axons from inside the eye to the thalamus.
These axons are gathered into a bundle, the optic nerve, which exists in each eye.
blind spot
because your eyes are a little far away from each other, the blind spot for each eye covers a different region. The brain normally fills in this gap without you even being aware of it.
