SENSATION and PERCEPTION

Sensation and Perception

• Sensation: The process of gathering data from the environment through sensory organs.

• Perception: The interpretation and understanding of sensory data.

• Perception is divided into three stages:

  • Sensation

  • Perceptual organization

  • Identification

The Visual System

• The eye functions like a camera, focusing light through lenses that gather and direct that light to the retina.

• Light enters through the cornea and passes through the aqueous humor, the pupil, and the lens before striking the retina.

• The lens accommodates for distance and near focus by changing its shape.

Sensory Knowledge of the World

• Proximal stimulus: Optical image on the retina.

• Distal stimulus: Actual object or event in the environment.

• For accurate perception, the difference between distal and proximal stimuli must be recognized.

Psychophysics

• Absolute thresholds: The minimum sensory level at which stimuli can be detected.

  • Measures through tasks such as detecting dim lights or soft sounds under varying conditions.

• Difference thresholds: The minimum difference in stimulus intensity required to detect a difference.

  • JND (Just Noticeable Difference) helps measure psychological differences.

• Weber's Law: The JND is a constant fraction of the intensity of the standard stimulus.

Sound Perception

• Sound originates from vibrations that create waves in air (or other mediums).

• Key properties of sound waves:

  • Frequency: Determines pitch, measured in Hertz (Hz).

  • Amplitude: Determines loudness, measured in decibels (dB).

The Physiology of Hearing

• Hearing involves membrane's vibrations.

  1. Vibrations convert into electrical impulses.

  2. Impulses are transmitted to the auditory cortex.

Theories of Pitch Perception

• Place Theory: Frequency sensitivity correlates with specific locations along the basilar membrane.

• Frequency Theory: Pitch is conveyed through the rate of firing neurons matched to sound frequency.

  • Volley principle suggests multiple neurons can combine their firing rates to encode higher frequencies.

Sound Localization

• Sound localization is achieved through:

  • Comparing the timing of sound arriving at both ears.

  • Assessing the relative intensity of sounds that reach each ear.