• Sensation
– The sense organs’ detection of external physical stimulus and the transmission of
information about this stimulus to the brain
• Perception
– The processing, organization, and interpretation of sensory signals in the brain; these
processes result in an internal neural representation of the physical stimulus
– Sensory receptors: Sensory organs that detect physical stimulation from the external
world and change that stimulation into information that can be processed by the brain
– Transduction: A process by which sensory receptors change physical stimuli into signals
that are eventually sent to the brain
– Absolute threshold: The smallest amount of physical stimulation required to detect a
sensory input half of the time it is present
– Difference threshold: The minimum difference in physical stimulation required to detect
a difference between sensory inputs
• Weber’s law
• Just noticeable difference
– Detection of a faint stimulus requires a judgment—it is not an all-or-none process
• Signal detection
theory helps us
understand how a
person can be
biased toward
either responding
or not responding,
despite being given
the same amount of
sensory input
– Sensory Adaption: A decrease in sensitivity to a constant level of stimulation
– Focusing light in the eye
– The light waves pass through the cornea of the eye
– The light then passes through the pupil
, – The iris, a circular muscle, gives eyes their color and controls the pupil’s size to
determine how much light enters the eye
– Lens: The adjustable, transparent structure behind the pupil; this structure focuses light
on the retina, resulting in a crisp visual image
– The thin inner surface of the back of the eyeball; this surface contains the sensory receptors
– Rods: Sensory receptors in the retina that detect light waves and transduce them into
signals that are processed in the brain as vision. Rods respond best to low levels of
illumination, and therefore do not support color vision or detection of fine detail
– Cones: Sensory receptors in the retina that detect light waves and transduce them into
signals that are processed in the brain as vision. Cones respond best to higher levels of
illumination, and therefore they are responsible for letting us see color and fine detail
– Each retina holds approximately 120 million rods and 6 million cones. Near the
center of the retina is a small region called the fovea where cones are densely
packed
– Information about what the eye has sensed is delivered to the ganglion cells
– The axons of each ganglion cell are gathered into a bundle. This bundle is called the optic
nerve
– There are blind spots in your left and right visual fields, where the optic nerve exits the
retina
– Half of the axons in the optic nerves cross to the other side of the brain. The rest of the
axons stay on the same side of the brain.
– The point where the axons cross is known as the optic chiasm
– The information passes through the thalamus and travels to the primary visual cortex in
the occipital lobes
– For humans, visible light consists of electromagnetic waves ranging in length from about
400 to 700 nanometers
– The amplitude is the height of the light wave from base to peak; people
experience this quality as brightness
– The wavelength of the light wave is the distance from peak to peak. This
distance determines your perception of both hue and saturation
– Hue refers to the distinctive characteristics that place a particular color in the
spectrum
– Saturation is the intensity of the color
– The combining of wavelengths is called additive color mixing
– The sense organs’ detection of external physical stimulus and the transmission of
information about this stimulus to the brain
• Perception
– The processing, organization, and interpretation of sensory signals in the brain; these
processes result in an internal neural representation of the physical stimulus
– Sensory receptors: Sensory organs that detect physical stimulation from the external
world and change that stimulation into information that can be processed by the brain
– Transduction: A process by which sensory receptors change physical stimuli into signals
that are eventually sent to the brain
– Absolute threshold: The smallest amount of physical stimulation required to detect a
sensory input half of the time it is present
– Difference threshold: The minimum difference in physical stimulation required to detect
a difference between sensory inputs
• Weber’s law
• Just noticeable difference
– Detection of a faint stimulus requires a judgment—it is not an all-or-none process
• Signal detection
theory helps us
understand how a
person can be
biased toward
either responding
or not responding,
despite being given
the same amount of
sensory input
– Sensory Adaption: A decrease in sensitivity to a constant level of stimulation
– Focusing light in the eye
– The light waves pass through the cornea of the eye
– The light then passes through the pupil
, – The iris, a circular muscle, gives eyes their color and controls the pupil’s size to
determine how much light enters the eye
– Lens: The adjustable, transparent structure behind the pupil; this structure focuses light
on the retina, resulting in a crisp visual image
– The thin inner surface of the back of the eyeball; this surface contains the sensory receptors
– Rods: Sensory receptors in the retina that detect light waves and transduce them into
signals that are processed in the brain as vision. Rods respond best to low levels of
illumination, and therefore do not support color vision or detection of fine detail
– Cones: Sensory receptors in the retina that detect light waves and transduce them into
signals that are processed in the brain as vision. Cones respond best to higher levels of
illumination, and therefore they are responsible for letting us see color and fine detail
– Each retina holds approximately 120 million rods and 6 million cones. Near the
center of the retina is a small region called the fovea where cones are densely
packed
– Information about what the eye has sensed is delivered to the ganglion cells
– The axons of each ganglion cell are gathered into a bundle. This bundle is called the optic
nerve
– There are blind spots in your left and right visual fields, where the optic nerve exits the
retina
– Half of the axons in the optic nerves cross to the other side of the brain. The rest of the
axons stay on the same side of the brain.
– The point where the axons cross is known as the optic chiasm
– The information passes through the thalamus and travels to the primary visual cortex in
the occipital lobes
– For humans, visible light consists of electromagnetic waves ranging in length from about
400 to 700 nanometers
– The amplitude is the height of the light wave from base to peak; people
experience this quality as brightness
– The wavelength of the light wave is the distance from peak to peak. This
distance determines your perception of both hue and saturation
– Hue refers to the distinctive characteristics that place a particular color in the
spectrum
– Saturation is the intensity of the color
– The combining of wavelengths is called additive color mixing
