Sensing the Environment

Question 1

Sensation

Answer 1

The conversion of physical stimuli into electrical signals that are transferred through the nervous system by neurons.

Question 2

Threshold

Answer 2

Absolute threshold is the lowest intensity of a stimulus that can be sensed.
A difference threshold describes the smallest difference that is sufficient for a change in stimulus to be noticed.

Question 3

Weber’s Law

Answer 3

The change required to meet the difference threshold is a certain fraction of the originally presented stimulus.
The fraction is constant for each sense.

Question 4

Signal Detection Theory

Answer 4

Focuses on how an organism differentiates important signals from noise in an environment where the distinction is ambiguous.
Ability to differentiate between signals and noise increases an organism’s change of survival.
Sensitivity can be expressed as a comparison between the false alarm rate and the hit rate.
There is always some amount of error in the process of distinguishing signal from noise.

Question 5

Sensory Adaptation

Answer 5

Sensory receptors change their sensitivity to the stimulus.
Dark adaptation (adaptation to reduced light intensity) involves immediate enlargment of the pupil, increased sensitivity of the cones (color receptors), increased sensitivity of the rods (night-vision receptors).
Light adaptation-opposite of dark adaptation.
Hearing – loud sound causes a small muscle attached to one of the bones of the inner ear to contract, reducing the transmission of sound vibrations to the inner ear, where the vibrations are detected. (This protective mechanism does not work well for sudden very loud noises such as rifle shots, as the muscle does not have time to contract before the intense vibrations pass through.)
Touch – We quickly adapt to hot and cold stimulation, if it is not too intense. The bath that was almost too hot to enter soon feels too cool; similarly, the cold lake we jump into for a summer swim feels freezing at first, but soon feels only refreshingly cool.
Smell – We can detect amazingly low concentrations of some chemicals in the air (e.g., perfumes) but although the perfume is still in the air about us, we quickly cease to detect it.

Question 6

Psychophysics

Answer 6

Quantitatively investigates the relationship between physical stimuli and the sensations and perceptions they affect.

Question 7

Sensory receptors

Answer 7

Cells the body uses to detect internal and external stimuli.
Five types of sensory receptors: mechanoreceptors for touch, thermoreceptors for temp. change, nociceptors for pain, electromagnetic receptors for light, and chemoreceptors for taste, smell and blood chemistry.