Sensation and perception
Introduced| English | Meaning |
|---|---|
| sensation/senˈseɪʃn/ | The detection and initial encoding of physical stimuli by sensory receptors and the nervous system. |
| perception/pəˈsepʃn/ | The organisation and interpretation of sensory information to form an experience of the environment. |
| absolute threshold/ˈæbsəluːt ˈθreʃəʊld/ | absolute threshold |
| difference threshold/ˈdɪfrəns ˈθreʃəʊld/ | difference threshold |
| perceptual constancy/pəˈseptʃuːəl ˈkɒnstənsi/ | perceptual constancy |
| illusion/ɪˈluːʒn/ | illusion |
The same image can invite two readings
- An ambiguous drawing looks like a vase or two faces. Detecting its light pattern and interpreting its shape are different processes.
- Sensation 感觉 detects stimulation; perception 知觉 interprets sensory information. An interpretation uses the input and context.
The eye detects wavelengths of light. What is that?
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Detection by a sense organ is sensation. Seeing red is the brain's interpretation, which is perception.
Use a detection criterion
- The absolute threshold 绝对阈限 is commonly defined as the stimulus level detected on 50% of trials under specified conditions. It is not a guarantee of detecting every weaker or stronger signal.
- The difference threshold 差别阈限 concerns a just-noticeable change. Weber’s proportional relation is an approximation over relevant ranges, not a law for every intensity.
Adding one candle is noticeable in a room with two but not with fifty. What does this show?
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The example illustrates the approximate proportional relation of a just-noticeable difference. It is not universal at every intensity.
Explain stable objects and changing views
- Perceptual constancy 知觉恒常性 helps an object retain perceived properties as viewing conditions change. A door can still look rectangular when its retinal projection changes.
- An illusion 错觉 can reveal how interpretation works. It may arise from contextual cues; it does not prove every illusion has one cause or that perception is generally useless.
A door swinging open projects a changing shape on the eye, yet you see one rectangular door.
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That is perceptual constancy: the brain holds the object steady while the input changes.
Check the alternative interpretation
- In the vase-and-faces drawing, the same boundaries can be treated as edges of different objects. Ask which region is being treated as the figure.
- A lighting-based illusion instead uses shading cues. State the actual cue in the supplied image rather than applying one explanation to every illusion.
What can an illusion reveal about perception?
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An illusion can help investigate interpretation and context. Its mechanism needs to be identified for the particular example.
A light is detected in half the trials at a stated intensity. What does that intensity describe?
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The common threshold criterion is detection on 50% of trials, with the procedure and conditions specified.
Keep the processes distinct
- A hearing example separates detecting vibrations from recognising a familiar tune. Recognition also uses prior information.
- Explain the detection, interpretation and relevant context. A threshold needs a procedure and criterion, not just “the smallest thing anybody can notice”.
Explain the detection, interpretation and relevant context. A threshold needs a procedure and criterion, not just “the smallest thing anybody can notice”.
Read more: Sensation and perception: threshold definitions.
In one sentence, explain the difference between sensation and perception using an example.
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Example: "The ear senses air vibrations, but perceiving them as a familiar song is the brain's interpretation."