Sensation
Introduced| English | Meaning |
|---|---|
| Sensation/senˈseɪʃn/ | The detection and initial encoding of physical stimuli by sensory receptors and the nervous system. |
| transduction/trænsˈdʌkʃn/ | transduction |
| threshold/ˈθreʃəʊld/ | A boundary value at which a specified effect begins or a decision changes. |
| just-noticeable difference/dʒʌst ˈnəʊtɪsəbl ˈdɪfrəns/ | The smallest change you can detect. |
| Weber's law/ˈwebəz lɔː/ | Weber's law |
| Sensory adaptation/ˈsensəri ˌædæpˈteɪʃn/ | Reduced sensitivity after constant, unchanging stimulation. |
| retina/ˈretɪnə/ | The light-sensitive layer at the back of the eye that converts light into nerve signals. |
| visual accommodation/ˈvɪʒuːəl əˌkɒməˈdeɪʃn/ | Changing the shape of the eye's lens to focus images from different distances onto the retina. |
| Rods/rɒdz/ | Retinal receptor cells that are highly sensitive in dim light and do not provide colour discrimination. |
| cones/kəʊnz/ | Retinal receptor cells supporting colour vision and fine detail under brighter lighting. |
| trichromatic theory/ˌtrɪkrəʊˈmætɪk ˈθɪəri/ | The account of colour vision based on the relative activity of three types of cone receptors. |
| opponent-process theory/əˈpəʊnənt ˈprəʊses ˈθɪəri/ | In colour vision, the account that signals are processed in opposing channels such as red-green and blue-yellow. |
| pitch/pɪtʃ/ | The perceived highness or lowness of a sound, strongly related to its frequency. |
| loudness/ˈlaʊdnəs/ | The perceived intensity of a sound, influenced by its physical intensity, frequency and the listener. |
| Olfaction/ɒlˈfækʃn/ | The only sense not routed through the thalamus; gustation has sweet, sour, salty, bitter, umami and oleogustus. |
| gustation/ɡʌˈsteɪʃn/ | gustation |
| Gate control theory/ɡeɪt kənˈtrəʊl ˈθɪəri/ | Gate control theory |
| vestibular sense/veˈstɪbjʊlə sens/ | The sense of head movement and orientation provided by structures in the inner ear, supporting balance. |
| kinesthesis/ˈkaɪnsθəsɪs/ | kinesthesis |
You stop noticing the clock after a minute
- A sound that was obvious becomes unnoticeable while it is still there.
- Your senses are not recording devices — they report change.
- This lesson is about how the body turns physical energy into a signal, and what it discards.
Sensation and transduction
- Sensation 感觉 is detecting information from the environment that meets a certain threshold 阈限, and turning it into a neural signal.
- That conversion is transduction 换能.
- Below threshold, the stimulus is present but produces no signal at all.
Sensation: receptors transduce energy into neural signals that travel to the brain
Converting a physical stimulus into a neural signal is called ____.
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Transduction is the conversion step; below threshold no signal is produced at all.
Detecting change, and stopping
- The just-noticeable difference 最小可觉差 is the smallest change you can detect.
- Weber's law 韦伯定律 says that difference is a proportion of the original, not a fixed amount.
- Sensory adaptation 感觉适应 is the diminished response to an unchanging stimulus — the clock you stop hearing.
Weber's law says the just-noticeable difference is...
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One spoon of sugar is detectable in a cup and not in a jug — the proportion is what matters.
Sensory adaptation is not the same as habituation. Adaptation happens in the sense organ itself — the receptors stop responding. Habituation is a learned drop in response that happens in the brain. The exam distinguishes them.
Which sensory system?
Sort each structure or term into the sense it belongs to.
The CED says colour vision is explained by the trichromatic theory alone.
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Colour vision is explained by both the trichromatic and the opponent-process theories.
Vision, in the terms the exam uses
- The retina 视网膜 is the photosensitive surface at the back of the eye; the lens focuses light onto it by visual accommodation 视觉调节.
- Rods 视杆细胞 in the periphery detect shape and movement but not colour; cones 视锥细胞 detect colour and detail.
- Colour vision is explained by both the trichromatic theory 三色理论 and the opponent-process theory 对立过程理论.
Select all that belong to the body senses rather than vision or hearing.
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The retina is part of the visual system; the other three are body senses.
Match each term to the sense it belongs to.
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Rods and cones code light, place theory codes pitch, and olfaction bypasses the thalamus.
Hearing, chemistry, touch and balance
- Sound is air movement: wavelength gives pitch 音高 and amplitude gives loudness 响度. Pitch perception is explained by place, volley and frequency theories.
- Olfaction 嗅觉 is the only sense not routed through the thalamus; gustation 味觉 has sweet, sour, salty, bitter, umami and oleogustus.
- Gate control theory 闸门控制理论 describes pain being processed in body and brain together.
- The vestibular sense 前庭觉 gives balance; kinesthesis 动觉 gives the sense of your own body's movement.
Add one spoon of sugar to a cup of tea and you taste the difference. Add one spoon to a large jug and you do not. The amount added is identical — what changed is the proportion, which is exactly what Weber's law predicts.
Sensation detects stimuli above threshold and transduces them into neural signals. The just-noticeable difference follows Weber's law as a proportion, and sensory adaptation removes unchanging stimuli. Vision uses rods and cones with two colour theories; hearing codes pitch and loudness; and vestibular and kinesthetic senses track balance and body movement.
Write from a just-noticeable difference of 20 g
- A 100 g weight needs an extra 2 g before the change is noticed. A 1000 g weight is judged by the same proportion.
- Find the extra mass needed on the heavier weight.
A change of 2 g is just noticeable on a 100 g weight. Using the same proportion, what change is just noticeable on a 1000 g weight?
2 percent of 1000 g is 20 g. The heavier starting stimulus needs a larger absolute change.
What change is just noticeable on the 1000 g weight?
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The proportion stays 2 percent, so 1000 g needs 20 g. Other options — 2 g (the same absolute spoon of sugar as in the lesson); 1000 g (the whole weight).