1.6 Sensation

Explain how the process of sensation is related to behavior and mental processes.

• Sensation is the process of detecting information from the environment that meets a certain threshold and transducing stimuli into neurochemical messages for processing (perception) in the brain. The absolute threshold occurs when a stimulus can be detected at least 50% of the time.
• Detection of change in stimuli or diminished sensitivity to stimuli can be explained by the just-noticeable difference and sensory adaptation. Weber’s law describes the degree to which stimuli need to be different for the difference to be detected.
• The sensory systems constantly work together in a process called sensory interaction. Synesthesia is an experience of sensation in which one system of sensation is experienced through another.

Explain how the structures and functions of the visual sensory system relate to behavior and mental processes. UNIT 1 Biological Bases of Behavior

• The retina is the photosensitive surface at the back of the eye. Cells in the retina capture visual information that is transduced to the brain for processing. Evidence of incomplete images captured by the retina is demonstrated by the presence of the blind spot, where the visual nerve exits the eye. The brain fills in the gaps in the incomplete retinal images to perceive a relatively complete picture of the world.
• Visual stimuli are focused onto the retina by the lens via a process called accommodation. When this process is altered, nearsightedness or farsightedness can result.
• Cells that lie in the periphery of the eye and detect shapes and movement, but not color, are called rods. These cells are mainly activated in low-light environments. These cells play a role in light and dark adaptation.
• Color vision is explained by both the trichromatic theory and the opponent-process theory.
  • i. Photoreceptor cells located in the fovea of the eye that process color and detail are called cones. Researchers have identified blue (detecting short wavelengths), green (detecting medium wavelengths) and red (detecting long wavelengths) cones in the retina.
  • ii. Afterimages result when certain ganglion cells in the retina are activated while others are not. The ganglion cells involved in this opponent process are red/green, blue/ yellow/ and black/white.
  • iii. Color vision deficiency involves damage or irregularities to one or more cones or ganglion cells (red/green, blue/ yellow). Color vision deficiency includes dichromatism or monochromatism.
• Damage to parts of the brain responsible for vision (mainly the occipital lobes) can result in disorders such as prosopagnosia (face blindness) and blindsight.

Explain how the structures and functions of the auditory sensory system relate to behavior and mental processes.

• Sound occurs through the movement of air molecules at different wavelengths (called pitch) and amplitudes (called loudness).
• Theories that help explain pitch perception include place theory, volley theory, and frequency theory.
• Sound localization describes how we identify where sounds in our environment are coming from.
• Hearing difficulties can result from aging and various kinds of damage to auditory structures. Types of hearing loss include conduction deafness and sensorineural deafness.

Explain how the structures and functions of the chemical sensory systems relate to behavior and mental processes.

• Structures in the nose and brain process and/ or transduce olfactory stimuli. Smell is the only sense not processed first in the thalamus of the brain. Pheromones produce chemical messages for the olfactory system.
• Gustation is the sense of taste, and types of tastes include sweet, sour, salty, bitter, umami, and oleogustus.
• Structures in the tongue, mouth, and brain process and/or transduce basic tastes. The number of taste receptors on the tongue is related to how sensitive people are to tastes, classifying them as supertasters, medium tasters, or nontasters.
• The chemical senses interact to create the sensation of taste. Without the sense of smell, taste sensations are either muted or not experienced.

Explain how the structures and functions of the touch sensory system relate to behavior and mental processes.

• Structures within the skin and brain process and/or transduce touch stimuli. The sensation of “hot” is produced by the activation of warm and cold receptors in the skin. WLEDGE

Explain how the structures and functions of the pain sensory system relate to behavior and mental processes.

• Pain is processed both in the body and in the brain. Gate control theory is one attempt to describe the complexities of pain. Phantom limb sensation occurs when people who have lost limbs report sensation or pain where the limb used to be.

Explain how the structures and functions that maintain balance (vestibular) and body movement (kinesthetic) relate to behavior and mental processes.

• The vestibular sense controls balance and is primarily detected by the semicircular canals and structures in the brain.
• Kinesthesis the sense of one’s body movement. Kinesthesis allows the body to move in coordinated ways without having to look at the various parts of the body as it moves. 46 AP PSYCHOLOGY UNIT 2 Cognition 15–25% AP EXAM WEIGHTING ~17–23 CLASS PERIODS 47 | Remember to go to AP Classroom to assign students the online Progress Check for this unit. Whether assigned as homework or completed in class, the Progress Check provides each student with immediate feedback related to this unit’s topics and skills. Progress Check 2 Multiple-choice: ~25 questions Free-response: 2 questions