Psychology Chapter: Sensation and Perception

Sensation

• Sensation is the process of detecting physical energy from the environment and converting it into neural signals.
• Perception is the process of selecting, organizing, and interpreting sensations.

Sensory Processing

• Transduction: Converting physical energy into neural signals.
  • Different sense organs detect different types of stimuli (e.g. light, sound, taste).
  • Each stimuli are converted into specific neural energy.
• Sensory coding: Representing characteristics of a stimulus.
  • Anatomical coding: Identifies location and type of sensory stimulus from which nerve fibers are activated
  • Encoding stimuli in terms of which nerve fibers are firing.
• Psychophysics: Study of the relationship between stimuli and sensations.
  • Measuring the relationship between physical and psychological events
  • Helps to define how much stimulation is needed for detection
• Absolute threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time.
  • Examples include a candle flame seen from 30 miles away, the tick of a watch at 20 feet, a drop of perfume in a 6 room apartment .
  • Minimum amount of a stimuli to notice or detect.
• Just noticeable difference (JND): The smallest difference between two similar stimuli that can be distinguished.
  • Examples include difference in pressure, color, and loudness.
  • Minimum amount of stimuli needed for detection.
• Signal detection theory (SDT): Detecting stimuli amid background noise.
  • The study of detecting signals in noise.
  • SDT takes into account the person's sensitivity and criteria when looking for stimuli.

Bottom-up and Top-down Processing

• Bottom-up processing: Analysis that begins with stimulus sensory receptors and works up to higher levels of processing in the brain.
  • Perception begins with the sensory input from the external environment.
• Top-down processing: Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations.
  • Perception influenced by prior experience and knowledge.

The Eye

• Parts of the eye:
  • Cornea: Transparent tissue where light enters the eye.
  • Iris: Muscle that expands/contracts to change pupil size.
  • Pupil: Opening in the iris that regulates light.
  • Lens: Focuses light rays onto the retina.
  • Retina: Contains sensory receptors (cones and rods).
  • Sclera: White outer layer.
• Nearsightedness: Eye is too long, image focused in front of fovea
• Farsightedness: Eye is too short, image focused behind fovea.

Photoreceptors

• Rods: Sensitive to dim light, not color.
• Cones: Sensitive to color, not dim light.
• Photopigments: Chemicals within photoreceptors that respond to light.

Visual Information Processing

• Parallel processing: Processing several aspects of a stimulus simultaneously.
• Shape detection: Specific areas of the temporal lobe fire when seeing specific shapes, like faces, houses, chairs.

Colour Vision

• Hue: Dimension determined by wavelength of light.
• Brightness: Dimension determined by intensity.
• Saturation: Intensity of a dominant wavelength relative to the total amount of light.
• Colour Mixing: How colours are mixed to create new ones.
  • Additive and Subtractive colour mixing.
• Colour blindness: Defect in colour vision, including protanopia, deuteranopia, and tritanopia issues.
  • Different types of colour blindness affect the perceivable colours.

Eye Movements

• Vergence movements: Cooperative movements of the eyes.
• Saccadic movements: Rapid movements used scanning.
• Pursuit movements: Movements made to keep a moving object on the fovea.