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Class 11 Sensory, Attentional and Perceptual Processes: cheat sheet
CBSE Psychology. How senses register stimuli, thresholds, the kinds and theories of attention, Gestalt organisation, depth cues, constancies and illusions.
Key ideas
- Sensation is the first registration of a stimulus; attention selects some stimuli; perception gives them meaning.
- The absolute threshold is the least stimulus that can be noticed; the difference threshold is the least change that can be told apart.
- Attention can be selective, divided (possible for well-practised, automatic tasks) or sustained (vigilance).
- Broadbent’s filter blocks unattended stimuli, Treisman’s only weakens them, and the multimode theory selects at three stages.
- Gestalt principles group what we see into wholes: proximity, similarity, continuity, closure, smallness, symmetry, surroundedness.
- Constancies keep size, shape and brightness stable as viewing conditions change; illusions are misperceptions of real stimuli.
- Bottom-up processing builds from features to the whole; top-down uses knowledge and expectations; both work together.
Remember
| Span of attention | seven plus or minus two items (Miller) |
| Properties of attention | alertness, concentration, search |
| Binocular depth cues | retinal disparity, convergence, accommodation |
| Monocular depth cues | relative size, interposition, linear and aerial perspective, light and shade, texture gradient, motion parallax |
| Deep senses | kinesthetic (body position) and vestibular (balance and movement) |
| Illusions | Müller-Lyer (equal lines look unequal); phi-phenomenon (still pictures seem to move) |
Watch out
- Mixing up the two thresholds: the absolute threshold is about noticing at all, the difference threshold about noticing a change.
- Calling a monocular cue binocular: only retinal disparity, convergence and accommodation need both eyes.
- Pairing the filter theory with Treisman: Broadbent gave the filter, Treisman the attenuation.
Worked example
Suppose plain water first tastes sweet after 5 grains of sugar, and tastes sweeter than before only after 9 more grains. What do the 5 and the 9 grains show, and how many grains are there in all?
Working: 5 + 9
Answer: 5 grains: the absolute threshold; 9 grains: the difference threshold; 14 grains in all
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