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Psychology

Unit 3

Sensation and Perception

6 topics · 24 practice questions · Free responseNot yet reviewed

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Notes

Basic ideas

  • Sensation detects energy; perception interprets it. Transduction converts stimuli into neural signals.
  • Absolute threshold is the minimum detectable stimulus; difference threshold is the smallest noticeable change. Weber's law: the JND is a constant proportion of the original stimulus. Sensory adaptation lowers sensitivity to constant stimuli.

The senses

  • Vision: light passes the cornea, pupil and lens to the retina. Rods work in dim light; cones detect color. Color vision uses trichromatic and opponent-process processes.
  • Hearing: the cochlea's hair cells transduce vibrations. Pitch is frequency; loudness is amplitude.
  • Touch, taste, smell and the body senses (vestibular and kinesthesis) also feed the brain. Gate-control theory explains how pain can be reduced.

Perception

  • Gestalt principles: figure-ground, proximity, similarity, continuity, closure.
  • Depth cues: binocular (retinal disparity) and monocular (relative size, overlap, linear perspective).
  • Constancies keep objects looking stable. Illusions, inattentional blindness and change blindness show the brain actively interprets input.

Topics in this unit

Each topic has its own short notes and practice.

Practice

A person walks from a bright street into a dark theater and at first sees nothing, but gradually sees better. The cells most responsible for adjusting to the dark are the:
Which statement best distinguishes sensation from perception?
A person can tell a 10-gram weight from an 11-gram weight about half the time. According to Weber's law, to notice a change in a 100-gram weight, the change would need to be about:
A cartoon of three separate arcs is seen as a circle because the brain fills in the gaps. This is the Gestalt principle of:
Which is a monocular depth cue?
Noah does not notice a large change in the background of a photo when it flickers between versions. This is:

Free response

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Free-response question

Priya walks into a bakery. At first the smell of bread is strong, but after ten minutes she barely notices it. She then focuses on reading the menu and does not hear the cashier call her name.

(a) Name the process that explains why Priya stops noticing the smell.

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Sensory adaptation: the receptors respond less to constant stimulation.

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(b) Explain why she did not hear her name, using one term from the unit.

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Her selective attention was focused on the menu, so she ignored the sound. This is similar to inattentional blindness, where attention limits what is noticed.

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(c) Distinguish sensation from perception using the smell of the bread as an example.

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Sensation is the detection of chemical molecules by smell receptors and their transduction into signals. Perception is the brain recognizing the signal as the smell of fresh bread.

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