Sensory Processing in Psychology 100

Sensory Processing in Psychology 100

Sensations

  • Definition of Sensations:

    • Sensations refer to the experience of stimuli from various sources including:

    • Electromagnetic waves

    • Skin sensations (e.g., pressure, temperature)

    • Compressed air waves (e.g., sound)

    • Volatile chemical compounds in the air (olfactory stimuli)

    • Chemical compounds in our mouth (taste)

    • Key Point: We only process a limited range of stimuli available in our environment.

Studying Sensory Processing

  • Methods to Study Sensory Processing:

    • Just Noticeable Differences (JND):

    • The smallest difference in stimulation that can be detected 50% of the time.

    • Fechner’s Law:

    • A principle that relates the intensity of a stimulus to the perception of its intensity. It expresses that the perceived change in stimulus intensity is proportional to the logarithm of the actual intensity, described mathematically as:

    • S = k \log{I}

      • Where S is the perceived sensation, I is the intensity of the stimulus, and k is a constant.

    • Subliminal Perception:

    • The phenomenon in which stimuli are presented below the threshold of conscious perception and may influence thoughts or behavior. This area remains controversial in psychology.

Vision

  • Nature of Vision:

    • Vision is based on electromagnetic waves, specifically visible light, which ranges from 400 nm (violet) to 700 nm (red).

    • Properties of visible light include:

    • Reflected Light:

      • What we perceive as color depends on the wavelengths reflected off objects.

      • White objects reflect the entire spectrum of visible light, while black objects absorb it.

    • Photons:

      • The smallest units of light waves.

Visible Spectrum

  • Wavelength Breakdown of Visible Light:

    • Visible Light Spectrum:

    • Ranges from approximately 400 nm to 700 nm.

    • Invisible Waves:

    • Infrared rays (longer than red) and Ultraviolet rays (shorter than violet).
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    • Diagram:

      Visual Spectrum Diagram

Dimensions of Visible Light

  • Key characteristics of light include:

    • Hue (Color):

    • The perceived color of light.

    • Saturation:

    • The intensity or purity of color.

    • Brightness:

    • Defined by the amplitude of light waves that contribute to visual perception.

Eye Structure and Function

  • How the Eye Works:

    • The eye transforms photons into neural signals through multiple components, such as:

    • Cornea:

      • The outer layer that focuses light and flips the image.

    • Aqueous Humor:

      • The fluid between the cornea and lens providing nourishment.

    • Iris and Pupil:

      • The iris regulates light entering the eye via the pupil.

    • Lens:

      • Adjusts to focus light on the retina (process called accommodation).

    • Retina:

      • Lined with photoreceptors that convert light into electrical signals.

Parts of the Eye

  • Key Components Include:

    • Ciliary Muscle:

      • A muscle that enables accommodation of the lens.

    • Fovea:

      • The area of the retina with a high concentration of cones for color vision.

    • Blind Spot:

      • The optic nerve exits the eye here, resulting in no photoreceptors.

Retinal Structure and Function

  • Photoreceptors:

    • Two main types exist in the retina:

    • Rods:

      • Sensitive to low light and motion; enables vision in dim conditions.

    • Cones:

      • Responsible for color vision and detail; three types sensitive to different wavelengths (red, green, blue).

    • Photopigments:

    • Composed of retinol and opsin, crucial for phototransduction (the conversion of light to electrical signals).

Rods and Cones Distribution in Retina

  • Distribution Overview:

    • Rods are more numerous in the peripheral areas of the retina, while cones are concentrated in the fovea.

    • Circuitry:

    • Light passes through layers of cells before reaching the photoreceptors (backwards construction of the retina).

Theories of Color Vision

  • Trichromatic Theory:

    • Proposes that color perception is based on the three types of cones (red, green, blue). Changes in the firing rates of these cones create our perception of color.

  • Opponent Process Theory:

    • Suggests that color perception is controlled by opposing pairs of colors (red-green, blue-yellow, black-white).

Visual Processing Pathway

  • Components:

    • Information travels from the retina through the optic nerve and converges at the optic chiasm, sending signals to the lateral geniculate nucleus and then to the primary visual cortex.

  • Complex Processing:

    • Simple Cells:

    • Detect specific edges and orientations of light in the visual field.

    • Dorsal Pathway (Where):

    • Processes motion and spatial awareness.

    • Ventral Pathway (What):

    • Involved in object recognition and identification.

Blind Sight

  • Definition:

    • A phenomenon in which individuals with damage to the primary visual cortex demonstrate the ability to respond to visual stimuli that they cannot consciously perceive.

Color Blindness

  • Types:

    • Color blindness arises from the absence or malfunction of photopigments in cones (often affects red or green cones). Assessment can be done using Ishihara plates.

    • Implications for vision in daily activities and professions.

Hearing

  • Stimuli for Hearing:

    • Sound is characterized by:

    • Frequency (Hertz, Hz)

    • Amplitude (decibels, dB)

    • Sound travels as waves featuring compression and rarefaction.

Ear Structures

  • Key Components Include:

    • Pinna:

    • Outer ear structure that captures sound waves.

    • Tympanic Membrane:

    • Also known as the eardrum; vibrates in response to sound waves.

    • Auditory Ossicles:

    • Include the malleus (hammer), incus (anvil), and stapes (stirrup), which amplify sound.

    • Cochlea:

    • A spiral structure that converts sound vibrations into electrical signals; houses hair cells organized along the basilar membrane.

Pitch Detection Theories

  • Frequency Theory:

    • Suggests that the frequency of the auditory nerve firing corresponds to the frequency of the sound wave.

  • Place Theory:

    • Posits that different frequencies trigger different places along the basilar membrane, leading to varying perception of pitch.

Deafness Types

  • Classification of Deafness:

    • Conductive Deafness:

    • Occurs when sound doesn’t travel well through the outer ear canal to the eardrum and the tiny bones.

    • Sensorineural Deafness:

    • Results from damage to the inner ear or the auditory nerve.

High Decibel Exposure and Associated Risks

  • Risk Levels:

    • Exposure to sounds above 85 dB can lead to hearing loss over time, with levels above 120 dB posing immediate danger.

  • Common Examples:

    • Decibel levels fluctuate significantly across environments, from normal conversations to jet engine noises.

Smell and Taste (Chemical Senses)

  • Olfaction:

    • The sense of smell utilizes roughly 5 million receptors of multiple types and relies on airborne molecules.

    • Olfactory Bulb:

    • Processes olfactory information and directly communicates with the cerebral cortex.

  • Taste (Gustation):

    • Humans have receptors for sweet, bitter, salty, sour, and umami tastes, with variations in sensitivity among individuals.

Skin Sensations

  • Types of Skin Sensations:

    • Include light touch, pressure, temperature (cold and heat), and pain.

    • Distribution of receptors varies across body regions and correlates with density mapped in the somatosensory cortex.

Sensory Adaptation

  • Definition:

    • Sensory adaptation occurs when there is a reduction in sensitivity to an unchanging stimulus; it illustrates the dynamic nature of sensory perception.

  • Related Concepts:

    • Habituation, sensory gating, and selective attention reflect more complex adaptive processes in response to sensory input.