Our brains need qualitative and quantitative information about a stimulus. Different
sensory receptors respond to qualitatively different stimuli. In contrast, quantitative
differences in stimuli are coded by the speed of a particular neuron firing – a more
rapidly firing neuron is responding at a higher frequency.
Coarse coding = sensory qualities are coded only be a few different types of
receptors, each of which responds to a broad range of stimuli.
Psychophysics = a subfield developed during the nineteenth century by the German
researchers Ernst Weber and Gustav Fechner, examines our psychological
experiences of physical stimuli. It assesses how much physical energy is required for
our sense organs to detect a stimulus. To test this, researchers present very subtle
changes in stimuli and observe how participants respond. They study the limits of
humans’ sensory systems.
The absolute threshold = the minimum intensity of stimulation that must occur
before you experience a sensation, or the stimulus intensity detected above chance.
The difference threshold = the just noticeable difference between two stimuli – the
minimum amount of change required for a person to detect a difference.
Weber’s Law states that the just noticeable difference between two stimuli is based
on a proportion of the original stimulus rather than on a fixed amount of difference.
Signal Detection Theory (SDT) = a theory of perception based on the idea that the
detection of a faint stimulus requires a judgment – it is not an all-or-none process.
Sensory adaptation = a decrease in sensitivity to a constant level of stimulation.
Gate control theory = for us to experience pain, pain receptors must be activated
and a neural “gate” in the spinal cord must allow the signals through the brain. Pain
signals are transmitted by small-diameter nerve fibres, which can be blocked at the
level of the spinal cord by firing of larger sensory nerve fibres.
Lateral inhibition = a visual process in which adjacent photoreceptors tend to
inhibit one another.
Subtractive color mixing = a way to produce a given spectral pattern in which the
mixture occurs within the stimulus itself and is actually a physical, not