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The nature versus nurture debate explores the relative influence of genetic (nature) and environmental (nurture) factors on behavior and development. Modern psychology recognizes that both play significant roles, often interacting in complex ways.
Heritability is a statistical measure that estimates how much of the variation in a trait within a population can be attributed to genes. Heritability does not apply to individuals, and traits can still be influenced by environmental factors, even if they are highly heritable.
Gene-environment interaction describes how genetic predispositions and environmental influences work together to shape behavior, personality, and mental processes. Nature provides the genetic basis, but nurture affects the expression and development of traits.
Researchers use family studies, twin studies, and adoption studies to explore how much a trait is influenced by genetics versus environmental factors.
Evolutionary psychology applies evolutionary principles to explain universal behaviors and psychological traits that may have evolved due to natural selection; that is, traits that provide a survival or reproductive advantage are more likely to persist across generations.
The nervous system consists of the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord, while the PNS includes sensory and motor neurons that connect the CNS to the rest of the body.
The peripheral nervous system (PNS) includes the autonomic nervous system, which controls involuntary bodily functions like heart rate and digestion, and the somatic nervous system, which controls voluntary muscle movements and sensory information processing.
The autonomic nervous system is divided into the sympathetic nervous system, responsible for the fight-or-flight response, and the parasympathetic nervous system, responsible for rest-and-digest functions.
The brain is divided into three regions: the hindbrain, midbrain, and forebrain. Each region is responsible for specific functions, including vital life functions, sensory processing, and higher-order cognition.
Neurons are the basic units of communication within the nervous system, transmitting electrochemical signals through action potentials and neurotransmitters. These processes enable many functions such as movement, sensation, learning, and emotional regulation.
Brain plasticity refers to the brain’s ability to reorganize itself by forming new neural connections, allowing for learning, memory, and recovery from brain injury. Plasticity is more robust during childhood but continues throughout life.
Sleep is essential for restoring physical and mental resources, with NREM sleep focusing on bodily restoration and REM sleep playing a key role in memory consolidation and cognitive function.
Psychologists assess the acuity of our senses by measuring the absolute threshold and the difference threshold and by applying signal detection theory.
Sensory adaptation is the decrease in sensitivity to an unchanging stimulus.
Babies are born with all the basic sensory abilities and some perceptual skills, which develop and become more sensitive over time.
The sense of vision depends on light, which is a kind of electromagnetic radiation emitted by the sun, stars, fire, and lightbulbs.
We experience light as color, brightness, and saturation, which depend respectively on wavelength, amplitude, and complexity of light waves.
The eye is composed of the cornea, the iris, the pupil, the lens, the retina, and the fovea. The lens adjusts its shape to focus light from objects that are near or far away in a process called accommodation.
Dark and light adaptation are processes by which receptor cells sensitize and desensitize to light, respectively.
The retina has millions of photoreceptor cells called rods and cones. Rods and cones connect via synapses to bipolar neurons, which connect to ganglion cells. The axons of the ganglion cells make up the optic nerve, which connects to the eye at the optic disk, also called the blind spot.
After being processed in the brain, visual signals reach the primary visual cortex, where feature detectors respond to the signals.
Color is a psychological experience created when the eyes and the brain interpret light.
Trichromatic theory, or the Young-Helmholtz theory, states that there are three types of cones in the retina, which are sensitive to light of different wavelengths corresponding to red, green, or blue. This theory accounts for color blindness.
The opponent process theory states that receptors act in opposite ways to wavelengths associated with three pairs of colors: red versus green, blue versus yellow, and black versus white. The theory accounts for the perception of four primary colors. It also accounts for afterimages, or colors perceived after other complementary colors are removed.
Hearing depends on sound waves. Sound has three features: loudness, pitch, and timbre, which depend respectively on wave amplitude, frequency, and complexity.
The ear comprises the outer ear, the middle ear, and the inner ear. These parts contain the pinna, the eardrum, ossicles, oval window, cochlea, and cilia.
Neurons in the ear form the auditory nerve, which sends impulses from the ear to the brain. The thalamus and auditory cortex receive auditory information.
Smell occurs when chemicals in the air are inhaled into the nose. Smell receptors send impulses along the olfactory nerve to the brain.
Kinesthesis is the sense of the position and movement of body parts.
The sense of balance gives information about where the body exists in space and involves the vestibular system.
The sense of touch encompasses pressure, pain, cold, and warmth.
The gate control theory of pain proposes that pain signals traveling from the body to the brain pass through a gate in the spinal cord. This gate is a pattern of neural activity that prevents pain signals or admits them.
