Perception
Introduced| English | Meaning |
|---|---|
| Perception/pəˈsepʃn/ | The organisation and interpretation of sensory information to form an experience of the environment. |
| Bottom-up processing/ˈbɒtəm ʌp ˈprəʊsesɪŋ/ | Building an interpretation from incoming sensory information. |
| Top-down processing/tɒp daʊn ˈprəʊsesɪŋ/ | Interpreting sensory information using prior knowledge, expectations and context. |
| Schemas/ˈskiːməz/ | Mental frameworks that organise knowledge and guide interpretation of new information. |
| perceptual sets/pəˈseptʃuːəl sets/ | perceptual sets |
| cultural expectations/ˈkʌltʃərəl ekspɪkˈteɪʃnz/ | cultural expectations |
| Attention/əˈtenʃn/ | The selection of particular information or activities for focused processing. |
| Gestalt/ɡəʃˈtɑːlt/ | Gestalt |
| closure/ˈkləʊʒə/ | The perceptual tendency to see incomplete shapes or patterns as complete wholes. |
| figure and ground/ˈfɪɡə ænd ɡraʊnd/ | The perceptual separation of a focal object or pattern from its surrounding background. |
| proximity/prɒkˈsɪmɪti/ | The perceptual tendency to group elements that are close together. |
| similarity/ˌsɪmɪˈlærɪti/ | The perceptual tendency to group elements that share features such as shape or colour. |
| Binocular cues/bɪˈnɒkjʊlə kjuːz/ | Depth information that depends on using both eyes, such as retinal disparity. |
| retinal disparity/ˈretɪnl dɪˈspærɪti/ | retinal disparity |
| convergence/kənˈvɜːdʒəns/ | convergence |
| Monocular cues/mɒˈnəʊkjʊlə kjuːz/ | Depth information available to one eye, such as overlap, relative size and linear perspective. |
| texture gradient/ˈtekstʃə ˈɡreɪdɪənt/ | A depth cue in which surface details appear smaller and more tightly packed with increasing distance. |
| linear perspective/ˈlɪnɪə pəˈspektɪv/ | A method of representing depth by making parallel lines appear to converge towards vanishing points. |
| interposition/ˌɪntəpəˈzɪʃn/ | A depth cue in which an object blocking part of another is perceived as nearer. |
| Perceptual constancies/pəˈseptʃuːəl ˈkɒnstənsiz/ | Perceptual constancies |
| apparent movement/əˈpærənt ˈmuːvmənt/ | The perception of motion produced by a sequence of stationary visual stimuli. |
Two people look at the same thing and see different things
- Sensation delivers the same raw data to both of them.
- What differs is what each brain does with it.
- Perception 知觉 is that second step — organising and interpreting sensation.
Bottom-up and top-down
- Bottom-up processing 自下而上加工 starts from the external sensory information itself.
- Top-down processing 自上而下加工 starts from what you already expect and know.
- Most perception uses both at once; questions ask which one a case relies on primarily.
Cover one eye: whatever still works is monocular
Reading messy handwriting easily because you know the words relies mainly on...
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Prior knowledge filling in unclear input is top-down processing.
The filters you bring with you
- Schemas 图式 and perceptual sets 知觉定势 are internal filters — frameworks that shape what you notice.
- Context, experience and cultural expectations 文化期待 are external filters.
- Attention 注意 is where sensation and perception meet, and it is affected by both kinds of filter.
An expectation that shapes what you notice before you notice it is a perceptual ____.
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A perceptual set is an internal filter, alongside schemas.
Do not use sensation and perception as synonyms. Sensation is detection and transduction; perception is organisation and interpretation. A question about why two people disagree about what they saw is always a perception question.
Select all Gestalt principles the CED names.
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Convergence is a binocular depth cue, not a Gestalt grouping principle.
Gestalt principles
- Gestalt 格式塔 psychology described how we group parts into wholes.
- The four the CED names are closure 闭合, figure and ground 图形与背景, proximity 邻近性 and similarity 相似性.
- Each one is the brain adding structure the sensory data did not contain.
Follow a stimulus from sensation to perception
Sensation is the signal; perception is what is made of it — and top-down expectation acts at the last step.
Perceptual constancy means an object looks different whenever its retinal image changes.
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Constancy does the opposite — it keeps the object the same to you despite the changing image.
Match each cue to what it uses.
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Disparity needs two eyes; interposition and texture gradient need only one.
Depth, constancy and movement
- Binocular cues 双眼线索 need two eyes: retinal disparity 视网膜像差 and convergence 辐辏.
- Monocular cues 单眼线索 work with one: relative clarity, relative size, texture gradient 纹理梯度, linear perspective 线条透视 and interposition 遮挡.
- Perceptual constancies 知觉恒常性 keep an object the same to you even as its retinal image changes; apparent movement 似动 is motion perceived where none occurs.
You read a handwritten note easily even though several letters are ambiguous. Bottom-up, the marks are unclear; top-down, your knowledge of the words fills them in. The same marks would be unreadable in a language you do not know.
Perception organises and interprets sensation, combining bottom-up and top-down processing. Schemas, perceptual sets, context and culture filter it. Gestalt principles group parts into wholes, binocular and monocular cues give depth, and constancies keep objects stable.
Write from a plate that still looks 50 cm across
- A 50 cm plate is seen at 2 m and again at 4 m.
- Say what happens to the perceived size.
A plate is 50 cm across. It is viewed at 2 m and then at 4 m. What happens to its perceived size, and why?
Doubling the distance does not make a familiar object look half as large.
How large does the plate look at 4 m?
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Size constancy keeps the perceived diameter at 50 cm. Other options — 25 cm (because the distance doubled); Unreadable marks (the lesson's handwritten note).