psy chap 4 pt 1

Introduction to Sensation and Perception

• Sensation and perception are often used interchangeably but refer to different concepts.

• The chapter covers general ideas applicable to all senses, focusing on waves for vision and hearing.

• Detailed exploration of sensory perception processes.

Sensory Receptors and Sensation

• Sensation involves activation of sensory receptors (neurons) responding to stimuli.

• Energy detected through senses triggers sensory organs, initiating sensation.

• Transduction: Process of converting energy (physical or chemical) into action potentials for the CNS.

Types of Senses

• Commonly recognized five senses include:

  • Vision

  • Hearing (auditory or audition)

  • Smell (olfaction)

  • Taste (gustation)

  • Touch (somatosensation)

• More sensory types include:

  • Thermoception: detection of temperature

  • Nociception: detection of pain

  • Vestibular sense: balance awareness (involves semicircular canals in ears)

  • Proprioception: awareness of body position in space

  • Kinesthesia: sense of movement through space

Absolute Threshold and Detection

• Absolute Threshold: Minimum energy required for detection at least 50% of the time.

  • Examples of absolute thresholds in senses:

    • Vision: Candle flame detectable from 30 miles in clear conditions.

    • Hearing: Ticking of a watch discernible from 20 feet away.

    • Touch: A bee wing landing on skin detectable.

    • Smell: A drop of perfume evident within two to three rooms.

    • Taste: One teaspoon of sugar in two gallons of water registers sweetness.

• Subliminal Messages: Activation of action potentials without conscious awareness, e.g. brief visual stimuli in films influencing behavior (e.g., product placement).

• Just Noticeable Difference (JND): Minimum difference between stimuli necessary for detection.

Processing Information: Sensation and Perception

• Perception: How the brain organizes and interprets sensory information.

• Types of processing:

  • Bottom-Up Processing: Analysis starts with sensory input, unfiltered by past experiences.

  • Top-Down Processing: Uses prior knowledge to interpret sensory information (e.g., ambiguous figures).

Factors Affecting Perception

• Sensory Adaptation: Diminished sensitivity to constant stimuli (e.g., odors or sounds that fade over time).

• Inattentional Blindness: Failure to notice unexpected stimuli when focusing on specific task (e.g., hidden objects in visuals).

• Motivation and Expectations: Influence on perceived stimuli; individuals may misperceive due to strong expectations (false positives).

• Cultural Influences: Different cultural backgrounds may alter perception (e.g., the Muller-Lyer illusion).

• Noisy Environments: Noise can interfere with perceptual clarity; relevant in both auditory and visual contexts.

  • Examples: Need to cleanse palate when tasting wines; distracting elements in 'Where's Waldo' illustrations.

Waves and Sensation

• Light and sound waves have distinct properties affecting our sensory experience:

  • Light Waves:

    • Properties: Amplitude (height = brightness) and wavelength (distance between peaks = color).

    • The visible spectrum: Ranges from 380 nm (violet) to 740 nm (red).

    • Wavelength correlations with color range (e.g., Infrared and UV).

  • Sound Waves:

    • Frequency: Number of cycles per second determining pitch (higher frequencies = higher pitch).

    • Amplitude: Loudness measurement (higher amplitude = louder sound).

    • Human hearing range: Approximately 20 Hz - 20,000 Hz.

Vision Mechanism

• Light enters the eye through:

  • Cornea: Protects and helps focus light.

  • Pupil: Opening that allows light to enter; size adjustment made by the iris (muscles around the pupil).

  • Lens: Focuses light onto the retina, can change shape for focus adjustment.

• Retina: Contains photoreceptor cells that convert light into neural signals for processing.

  • Fovea: Central retina area for sharp vision.

• Vision processing involves interpreting spatial orientations; images are inverted as they project onto the retina.

Blind Spots and Perception Integration

• Each eye has a blind spot where the optic nerve leaves; due to differing visual fields in each eye, perception compensates for blind spots.

• The brain integrates slightly different images from each eye to maintain a coherent view.