psy

Recap of prior discussion on visual perception (graph on stimulus intensity and detection ability).
- Subliminal perception: When stimulus cannot be consciously perceived.
- Supraliminal perception: When stimulus can be consciously perceived.

Objective: Explain why some sensory information is ignored.
- Habituation: The brain's tendency to stop attending to unchanging stimuli.
- Example: Living near train tracks, one may become unaware of the sound over time due to habituation.
- Sensory Adaptation: This occurs at the sensory receptor level, where receptor cells become less responsive to constant stimuli.
- Example: Jumping into a cold pool feels freezing at first, but sensation diminishes as receptors adapt to the temperature.
Micro Saccades: Tiny eye movements that prevent visual stimuli from fading due to sensory adaptation, keeping images refreshed.

Sensation: The process of receiving external information and relaying it to the brain.
Components:
- Activation of Sensory Receptors: Sensory organs have receptors that detect stimuli (light, sound, taste, touch, smell).
- Transduction: Conversion of sensory information into neural signals understood by the brain.
- Example: Light hit the eye and gets converted into signals for image processing.

Light's Nature: Light behaves as both waves and particles. Complex behavior includes:
- Wave Properties: Light can exhibit interference and diffraction like water waves (notable in double-slit experiments).
- Particle Properties: Light can behave as particles called photons, which have energy and momentum but no mass. Interaction with matter results in phenomena like the photoelectric effect.

Brightness: Determined by wave amplitude. Higher amplitude indicates brighter light.
Color (Hue): Determined by wavelength; longer wavelengths appear red, and shorter wavelengths appear blue.
Saturation: Refers to color purity; a highly saturated color is pure, while a less saturated color may appear as a mix of wavelengths.
Electromagnetic Spectrum Overview: Displays various electromagnetic radiation forms, including visible light, ultraviolet, and gamma rays arranged by wavelength and energy.

Light is transduced into two features:
- Wavelength: Determines color perception; light waves between 400 nm (violet) and 750 nm (red) represent the visible spectrum.
- Intensity: Higher intensity translates to perceived brightness.
Rattlesnake capability: Can see infrared light, which assists in hunting.

Process: Light enters the eye through cornea and pupil, with the iris controlling pupil size based on light levels.
Components Include:
- Cornea: A protective dome refracting light; its curvature is fixed but can be compromised (e.g., myopia, hyperopia).
- Aqueous Humor: Nourishes the eye and resides between cornea and pupil.
- Lens: Completes the focusing process, changes shape for accommodation, and hardens with age (presbyopia).
- Vitreous Humor: Jelly-like fluid maintaining eye shape and providing nourishment.

Retina: Contains rods (night vision; peripheral vision) and cones (color vision; central vision clarity).
- Rods: Sensitive to low light, providing gray images.
- Cones: Operate best in bright light; three cones (red, green, blue) for color vision.
Blind Spot: Area where optic nerve exits, lacking photoreceptors.
Transduction: Conversion of light into neural signals occurs in the retina.
Dark and Light Adaptation:
- Dark Adaptation: Takes time for rods to adjust to lower light post-brighness.
- Night Blindness: Results from rod dysfunction.
- Light Adaptation: Adjusts eye sensitivity in bright conditions, occurring faster than dark adaptation.

Flow of Information:
1. Photoreceptors detect light and generate neural signals.
2. Signals travel via the optic nerve to the optic chiasm where information crosses between hemispheres (nasal half crosses, temporal half remains).
3. Proceed through the optic tract to the Lateral Geniculate Nucleus (LGN), then optic radiations to the primary visual cortex for image processing.

Trichromatic Theory: Proposed by Young and Helmholtz; suggests color perception stems from activation of three types of cones: red, green, blue.
Opponent Process Theory: Suggests color vision processes four primary colors. Neuronal responses can be excited by some colors and inhibited by others, helping explain afterimages (e.g., perceiving a complementary color after staring at a primary color).

Types:
- Monochromatic Vision: Can only see shades of one color (typically gray) due to cones being nonfunctional or damaged.
- Dichromatic Vision: Two cones function, often leading to difficulty distinguishing colors depending on which cone type is affected (e.g., red-green color deficiency).
Sex-linked Inheritance: Gene for color deficiency is recessive located on the X chromosome; males (one X) are more likely to be affected than females (two Xs).

Comparison of sound and light properties:
- Key properties include:
- Wavelength: Frequency/pitch of sound; shorter wavelengths correspond to higher pitches, longer to lower pitches.
- Amplitude: Determined volume levels in sound, influences how loud or soft the sound is.

Continual interactions between sensory systems, neurological pathways, and physical properties shape the way humans experience and interpret the world around them.
Understanding these processes provides foundational knowledge in psychological sensation and perception.