CBSE Class 11 — Notes, Chapters & Practice Quizzes

Chapter 4: Sensory, Attentional and Perceptual Processes

Summary

Our knowledge of the world depends on three interrelated processes: sensation, attention and perception. Sensation is the registration of stimuli by the sense organs, which respond only to stimuli within a certain range; the minimum amount of stimulus needed for detection is the absolute threshold and the smallest detectable change is the difference threshold. Different sense modalities (vision, hearing, smell, taste, touch) have specialised receptors. Attention is the selective process by which we focus on certain stimuli; it includes selective attention (governed by external factors such as size, intensity and novelty, and internal factors such as motivation and set), divided attention, and sustained attention or vigilance. Perception is the process of interpreting sensory information, using bottom-up and top-down processing. The Gestalt principles of perceptual organisation (figure-ground, proximity, similarity, continuity and closure) describe how we organise stimuli into meaningful wholes. Depth and distance are perceived through monocular cues (relative size, interposition, linear perspective, texture gradient, motion parallax) and binocular cues (retinal disparity, convergence). Perceptual constancies (size, shape, brightness) keep our perception stable, while illusions are mismatches between perception and reality. Socio-cultural factors, learning and experience also shape perception.

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