Psychology Chapter on Sensation and Perception

Sensation and Perception: Introduction and Measurement

• Sensation is the ability to detect a stimulus, potentially turning that detection into a conscious experience.
• Perception is the act of giving meaning to a detected sensation, allowing us to understand the world around us.
• Sensation and perception are vital for gaining knowledge of the environment.

Absolute Thresholds for Humans

• Vision: A candle flame seen at approximately 50 kilometers on a clear, dark night.
• Hearing: A ticking watch under quiet conditions at approximately 6 meters.
• Taste: A single teaspoon of sugar in approximately 7.5 liters of water.
• Smell: One drop of perfume diffused into a large apartment.
• Touch: A wing of a fly or bee falling on your cheek from a distance of 1 centimeter.

Psychophysics

• Psychophysics is the science that defines quantitative relationships between physical and psychological events.
• This establishes how physical stimuli relate to perceptual experiences.

Weber's Law

• Explains the smallest detectable change in a stimulus.
• The smallest noticeable difference (JND) is a constant proportion of the stimulus level.

Signal Detection Theory

• Quantifies an observer's response to a signal, considering background noise (both internal and external).
• Four possible outcomes in a signal detection scenario are considered: hits, misses, false alarms, and correct rejections.

Sensory Adaptation

• Diminishes sensitivity to unchanging stimuli.
• This allows perceptual systems to remain sensitive to changes in the environment.

The Human Eye

• Light passes through the cornea, pupil, and lens.
• The pupil adjusts size to regulate light entering the eye.
• Photoreceptors:
  • Rods: Function best in dim light, providing sensitivity. Found throughout the retina except the fovea.
  • Cones: Function best in brighter light, providing color vision and detail. Concentrated in the fovea at the center of the retina.

The Fovea

• Area in the center of the retina with high visual acuity.
• Contains only cones.

Perception Processing in Retina

• Rods and cones synapse with bipolar cells, which synapse with ganglion cells, creating the optic nerve.
• The axons of ganglion cells form the optic nerve.

Dark Adaptation

• Becoming sensitive to low illumination takes time.
• Progressive improvement in brightness sensitivity in low illumination.

Trichromatic Theory (Young-Helmholtz)

• Three types of color receptors (cones) in the retina that respond maximally to different wavelengths of light (blue, green, red).
• These signals combine to produce the perception of other colors.

Opponent-Process Theory

• Our visual system analyzes color in terms of opposites (red-green, blue-yellow, white-black).

Visual Pathways

• Specialized cells in the visual cortex (including feature detectors) analyze the visual stimulus into components.
• This happens in hierarchical fashion, building up more complex features from basic ones.

Visual Perception in the Primary Visual Cortex

• Visual information from the eye is projected to the lateral geniculate nucleus (LGN) of the thalamus.
• Then, this projected information is sent to the primary visual cortex (V1) within the occipital lobe.
• The fovea receives a large representation within the cortex, in order to receive and interpret visual information as detailed as possible.

Inferotemporal (IT) Cortex

• Important part of the temporal lobe.
• Crucial for object recognition.
• Lesions of this area cause deficits in object recognition (anosmia).
• It has very large receptive fields.
• Does not respond to simple stimuli like lines or spots. It responds effectively to complex objects like faces, hands, or objects.

Sound Localization

• Using subtle differences in how sounds arrive at both ears (interaural time and level differences).

Hearing Loss

• Various kinds of hearing loss: conduction deafness from issues with the outer or middle ear, or nerve deafness from issues in the inner ear (such as the cochlea). Different types of hearing loss respond differently to solutions.

Taste and Smell

• Taste (Gustation):
  • Chemical receptors on taste buds.
  • Four basic tastes: sweet, sour, salty, bitter, umami.
  • Individual differences in taste perception.
• Smell (Olfaction):
  • Chemical receptors in the nasal cavity.
  • Direct connection to the limbic system, influencing emotional responses and memory.
  • Relatively poor sense for humans.

Body Senses

• Kinesthesis: Provides feedback about muscle and joint positions.
• Vestibular Sense: Helps with equilibrium and orientation (in inner ear).

Gestalt Principles of Perceptual Organization

• Similarity: Items that are similar are perceived as belonging to the same group.
• Proximity: Items that are close together are perceived as a group.
• Closure: We tend to perceive incomplete figures as complete.
• Continuity: We tend to perceive continuous lines and patterns rather than disrupted ones.

Perception and Hypothesis Testing

• Perceptual schemas help us to interpret ambiguous stimuli based on our past experiences.
• Our perceptual systems seek clear, concise interpretations of ambiguous stimuli.
• Knowing that something is an illusion allows the observer to sometimes see through the illusion.

Critical Periods in Perception

• Specific periods are crucial for learning some perceptual abilities. Experiences during these periods can have lasting effects, such as the specific pattern perception in kittens.

Key Concepts for modules 1-3 (summarized)

• Module 1: Psychology's roots, scientific method, experimental designs.
• Module 2: Neuron function, nerve impulses, synaptic transmission, and brain structure.
• Module 3: Sensation and perception (from physical aspects of stimuli to how we build a sense of perception), sensory and perception pathways, cortical processing.

This quiz covers key concepts in sensation and perception, including absolute thresholds for hearing, taste, and vision, as well as Just Noticeable Difference in relation to Weber's Law. It also explores signal detection theory, auditory transduction, and the function of taste buds, among other topics. Test your knowledge on these foundational principles of psychology.