General Psychology
Sensation and Perception

 Introduction

1. The first law of life is survival.  Our sensory system informs us of our physical world and internal world (e.g., pain)

2. Physical world consists of infinite amount of information or stimuli.  From our evolutionary history we’ve developed five senses to select information relevant to our survival and functioning.

3. Our senses allow us to (a) see (eyes), (b) hear (ears), (c) taste (tongue), (d) smell (nose), and (e) feel (skin).  Each sense responds to a narrow range of information and differs from other species.  For us, as bi-peds, our vision is most important and developed.

Stimuli:

• Visual: Visible light within a certain wavelength and of a minimum amplitude.

• Auditory: Sound waves within a certain wavelength and a minimum amplitude.

• Taste: Chemical (sweet, sour, salty, and bitter)

• Smell: Gaseous molecules in the air.

• Touch: Min. physical (pressure, warmth, cold, pain).

Process:

• Deconstruction of stimuli

• Transduction of stimuli into neural impulses

• Reconstruction as an experience

Theories of Perception: 

• Ecological approach

  • we receive the world directly as it is.

  • evidence: great consensus on perceptions of the physical world.  Direct correspondence between outside world, our sensory systems, and our perceptions.

• Constructivist approach

  • our perceptions are constructed by the mind as a function of past experiences and expectations.

  • evidence: (a) unconscious influence, (b) influence from needs and values, and (c) assumptions/expectations. 

• Computational approach

  • our nervous system has a tendency--to organize stimuli into meaningful perceptions.

  • evidence: Gestalt psychology figure-ground, closure, proximity, meaning of context

Implications:

• Our experience of reality is only partial.
• We cannot experience reality directly, it is processed.
• Given the right artificial stimuli or brain chemistry we can theoretically imitate anything and everything.

Vision:

• The most important sense to humans with the basic functions to (1) detect objects in environment, (2) detect change, and (3) monitor own movement.
•  Structures of the eye:
  • Cornea: no blood supply
  • Pupil:  hole which light passes
  • Iris:  regulates light
  • Lens:  shapes image for retina
  • Retina: photoreceptors include rods (sensitive, b/w, 120 million, 1 hr adaptation) and cones (color,  6 million, 7 minute adaptation concentrated at fovea)
  • Intermediate layer transforms information into ganglion, Ganglion cells transform to optic nerve
•  Color vision:
  • Primates and nonmammals have excellent color vision.
  • Color is a function of wavelength.
  • Cones enzymes sensitive to red, green, blue.
  • Color a function of combinations via opponent process.
  • Color blindness (7-10% males).

Visual Perception

• Depth, Movement, and Illusions

  • Depth

    • apparent size compared to background, texture, brightness, linear perspective, interposition, binocular disparity.

  • Movement

    • Image across retina, eye stationary

    • Image constant but eyes or head moves

  • Illusions

    • persistence of vision (movies)

    • autokinetic phenomenon (light appears to move)

Hearing:

• Second most important sense: Locates and discriminates between sounds.

• Structure of the ear:

  • Outer: Pinna directs sound waves into auditory canal.

  • Middle: Amplifies sound waves with the ear drum and 3 bones (hammer, anvil, stirrup).

  • Inner: Transduction of wave into neurosignals. Wave hits cochlea which has liquid and sensory cells of the organ of Corti. Pressure released out the round windo and Eustachian tube.

• Responsive to sound wave amplitude (loud), frequency (pitch), timbre (harmonics), location in space, and duration.

ESP and Parapsychology

• Study of perceptions not attributable to the 5 senses.

• ESP research

  •  Mental telepathy (mind reading).  Some inconsistent evidence.

  • Precognition (perceiving future events) No evidence to support e.g., plane crash., child's injury, etc.

  • Psychokinesis (moving things) No evidence to support .

  • Clairvoyance (sensing remote events) No evidence to support.