Ch 6 Flashcards
Sensation
The processes of sensory responding and
of the sensory receiving areas of the
brain.
Perception
The process by which the brain organizes
and interprets sensory information.
Our Sensational Senses
Most students learn there are five senses, corresponding to five sense organs: Vision → eyes Hearing → ears Taste → tongue Touch →skin Smell → nose
The Riddle of Separate Senses
Doctrine of Specific Nerve Energies
The principle that different sensory modalities exist because signals received
by the sense organs stimulate different nerve pathways leading to different
areas of the brain.
Examples
Signals from the eye → travel along the optic nerve to the visual cortex.
Signals from the ear → travel along the auditory nerve to the auditory
cortex.
Synesthesia
A condition in which stimulation of one sense also evokes another. Examples Colour purple smells like a rose. Aroma of cinnamon feels like velvet.
Three Limitations of the Doctrine of Specific Nerve Energies
- Difficult to link the different senses to distinct nerve pathways.
- Can not explain variations within a particular sense.
Sight of pink versus red
Sound of a piccolo versus the sound of a tuba
Feel of a pinprick versus the feel of a kiss - Explains the experience of different kinds of sense sensations using only
anatomical codes.
Anatomical codes → Specific neural circuits signify particular sensory
experiences.
Functional codes→ Information about which cells are firing, how many
cells are firing, the rate at which cells are firing, and the patterning of
each cell’s firing signify particular sensory experiences.
Measuring our Senses
- Absolute Threshold
The smallest quantity of physical energy that can
be reliably detected by an observer.
Measuring our Senses: Absolute Sensory Thresholds
Vision
Candle flame on a clear, dark night from almost 50 km away.
Hearing
Tick of a watch in a perfectly quiet room from over 7 m away
Smell
1 drop of perfume diffused through a 3-room apartment.
Touch
Wing of a bee on your cheek, dropped from a height of 1 cm.
Taste
1 teaspoon of sugar in 2 gallons of water.
- Difference Threshold
The smallest difference in stimulation that can be reliably detected by an
observer when two stimuli are compared.
3.The Signal-detection theory
A psychophysical theory that divides the detection of a
sensory signal into a sensory process and a decision
process.
Sensory process is depends on the intensity of the
stimulus.
Decision process is influenced by the observer’s
response bias.
Sensory Adaptation
The reduction or disappearance of sensory
responsiveness when stimulation is unchanging or
repetitious.
Example
Sense of a watch on your wrist.
Sensory Deprivation
The absence of normal levels of sensory stimulation. Often occurs through prolonged isolation. The effects of sensory deprivation Hallucinations Disorientation Depression Irritability Restlessness
Two Types of Isolation
Involuntary Isolation Locked in a room for an indefinite period of time. Voluntary Isolation Choosing to take a little time-out. Visit to a luxury spa or a monastery
Sensing without Perceiving
Sensory overload
Overstimulation of the senses.
Selective attention
The focusing of attention on selected aspects of
the environment and the blocking out of others.
Protects from sensory overload.
Inattentional blindness
Failure to consciously perceive something you are looking at
because you are not attending to it.
Example
Focusing on listening to a voice on your cell.
Fail to see a pedestrian crossing the street in front of you.
Hue, Saturation and
Brightness
Perception of a colour depends on a mix of 3 dimensions. Hue Wavelength of light. Saturation Purity of light. Brightness Intensity of light.
The Visual Pathway
1. The Main Visual Pathway Thalamus: sensory relay. Primary visual cortex. Lateral geniculate nuclei. Secondary visual cortex. Temporal and parietal lobes. 2. The Second Visual Pathway: Coordination of visual input with other sensory input. Superior colliculus (midbrain). Thalamus. Occipital lobe.
The Main Visual Pathway
a. Magnocellular channel “Where pathway”. Perception of motion and depth. b. Parvocellular channel “What pathway”. Perception of colour, form and texture.
Feature Detector Cells
Much visual processing is done in the brain.
Some cortical cells respond to lines in specific
orientations (e.g., horizontal).
Other cells in the cortex respond to different shapes
(e.g., bulls-eyes, spirals, & faces).
The Trichromatic Theory
Support for the
Trichromatic Theory
The Trichromatic Theory proposes that the eye contains 3 colour receptors each differently sensitive to the various wavelengths of light. For any colour, the 3 receptors will produce a unique ratio of activity.
Evidence indicates 3 types of cone receptors as proposed by the Trichromatic theory.
Rod Monochromats
Non-functional cones,
poor visual acuity,
shades of grey.
Deuteranopia
Defective medium,
shades of blue and
yellow.