Chapter 4: Sensation and perception
Sensation: the physiological process of taking in raw physical energy from stimuli through the sensory receptors the sensory
receptors of our different sensory organs.
→ Involves absorption such as light to sound waves by sensory organs (eyes and ears)
Transduction: the conversation of raw physical energy into sensory neurological signals.
→ The sub process that occurs during sensation.
→ Sensation allows you to experience stimuli such as smelling a variety of scents or feeling different pressures on our skin.
Perception: a psychological process of selecting, organising and interpreting the sensory neurological signals that reach the
brain so that we can make sense of and attach meaning to sensations.
→ Involves organising and transplanting sensory input into something meaningful.
→ Distinction between sensation and perception
Both of them influence each other in terms of effect and impairment.
The visual system: Essentials of sight:
Humans are visual animals.
They rely heavily on sight, and they often equate sight with knowing what is trustworthy.
In all sensory domains, people “sense” and what they “perceive” may be quite different.
Visual systems enable us to see, recognise and perceive objects and people.
The stimulus: Sight
Light is a form of electromagnetic radiation that travels as a wave, moving, naturally enough at the speed of light.
Light vary in amplitude and wave length.
→ Amplitude: Affects mainly the perception of colour.
Light can also vary in purity
→ Purity: It influences the perception of saturation or richness of colour.
, As whiteness declines, saturation increases.
→ Most objects reflect light.
The visible spectrum of light is only a small portion of the total range of wavelengths.
→ Ex. Many insects can see shorter wavelengths than humans (fall under the ultraviolet spectrum).
→ Ex. Many fish and reptiles can see longer wavelengths (falls under the infrared spectrum)
Stimulus Intensity and threshold
Threshold: a point at which a stimulus triggers a response.
Fechner + his contemporaries = studied the minimal amount of stimulation required from a stimulus in order to stimulate a
psychological experience.
→ This was known as the stimulus intensity.
Stimulus intensity: How intense a stimulus has to be in order for it to be detected.
→ The weakest stimulus is a concept known to psychophysics= absolute threshold.
→ Fechner+ contemporaries suggested that the absolute threshold is NOT absolute and that gradual exposure to the stimuli
will lower the threshold.
Individuals don’t perceive stimuli at the same intensity.
Individuals do not perceive stimuli at the same intensity
Fechner considered a theory of Just Noticeable Difference (JND)
→ This aims to identify that the lowest intensity of stimulation needed to create a noticeable difference between stimuli.
This is also known as difference threshold
→ The JND is more apparent when strength between stimuli is set at greater levels of intensity
→ JND is also subjective because it is based on differing perceptions
One person may identify chance in sweetness after 10 grains of sugar are added and another person may only sense the
difference after 100 grains are added
Signal detection theory
Signal-detection theory: It emphasises the psychological state that influences the detection of a stimulus
Sensation: the physiological process of taking in raw physical energy from stimuli through the sensory receptors the sensory
receptors of our different sensory organs.
→ Involves absorption such as light to sound waves by sensory organs (eyes and ears)
Transduction: the conversation of raw physical energy into sensory neurological signals.
→ The sub process that occurs during sensation.
→ Sensation allows you to experience stimuli such as smelling a variety of scents or feeling different pressures on our skin.
Perception: a psychological process of selecting, organising and interpreting the sensory neurological signals that reach the
brain so that we can make sense of and attach meaning to sensations.
→ Involves organising and transplanting sensory input into something meaningful.
→ Distinction between sensation and perception
Both of them influence each other in terms of effect and impairment.
The visual system: Essentials of sight:
Humans are visual animals.
They rely heavily on sight, and they often equate sight with knowing what is trustworthy.
In all sensory domains, people “sense” and what they “perceive” may be quite different.
Visual systems enable us to see, recognise and perceive objects and people.
The stimulus: Sight
Light is a form of electromagnetic radiation that travels as a wave, moving, naturally enough at the speed of light.
Light vary in amplitude and wave length.
→ Amplitude: Affects mainly the perception of colour.
Light can also vary in purity
→ Purity: It influences the perception of saturation or richness of colour.
, As whiteness declines, saturation increases.
→ Most objects reflect light.
The visible spectrum of light is only a small portion of the total range of wavelengths.
→ Ex. Many insects can see shorter wavelengths than humans (fall under the ultraviolet spectrum).
→ Ex. Many fish and reptiles can see longer wavelengths (falls under the infrared spectrum)
Stimulus Intensity and threshold
Threshold: a point at which a stimulus triggers a response.
Fechner + his contemporaries = studied the minimal amount of stimulation required from a stimulus in order to stimulate a
psychological experience.
→ This was known as the stimulus intensity.
Stimulus intensity: How intense a stimulus has to be in order for it to be detected.
→ The weakest stimulus is a concept known to psychophysics= absolute threshold.
→ Fechner+ contemporaries suggested that the absolute threshold is NOT absolute and that gradual exposure to the stimuli
will lower the threshold.
Individuals don’t perceive stimuli at the same intensity.
Individuals do not perceive stimuli at the same intensity
Fechner considered a theory of Just Noticeable Difference (JND)
→ This aims to identify that the lowest intensity of stimulation needed to create a noticeable difference between stimuli.
This is also known as difference threshold
→ The JND is more apparent when strength between stimuli is set at greater levels of intensity
→ JND is also subjective because it is based on differing perceptions
One person may identify chance in sweetness after 10 grains of sugar are added and another person may only sense the
difference after 100 grains are added
Signal detection theory
Signal-detection theory: It emphasises the psychological state that influences the detection of a stimulus
