Psychology Chapter 6-9 PDF

6.1.01 Prenatal Development The prenatal period of development occurs during gestation, the time between conception and birth. Prenatal development is influenced by both nature and nurture. Nature refers to genetic influences on development (eg, genes coding for eye color), whereas nurture refers t...

6.1.01 Prenatal Development The prenatal period of development occurs during gestation, the time between conception and birth. Prenatal development is influenced by both nature and nurture. Nature refers to genetic influences on development (eg, genes coding for eye color), whereas nurture refers to nongenetic influences in the environment (eg, exposure to nicotine). For example, one\'s height is determined by both the genetic information passed down from their parents and the influence of their environment, such as the nutrition they received during gestation. A [teratogen](javascript:void(0)) is any factor (eg, a drug or virus) that negatively impacts prenatal development. For example, consumption of alcohol, a teratogen, during pregnancy can lead to fetal alcohol syndrome. **Fetal alcohol syndrome** causes permanent negative effects to the fetus such as inhibited growth, facial deformities, and damage to the brain, resulting in lower intelligence. 6.1.02 Motor Development Humans are born with simple **reflexes**: automatic responses to sensory stimuli that aid in survival. Some of these reflexes include: The Moro reflex (also called the startle reflex), which causes an infant to throw back their head, extend their arms and legs, cry, and clench their arms and legs to their body when startled [Rooting](javascript:void(0)), which causes an infant to turn their head and open their mouth when stroked on the cheek The patellar reflex (also called the knee-jerk reflex), which causes the leg to extend when the patellar tendon (below the kneecap) is tapped The Babinski reflex, which causes an infant to bend their big toe back while their other toes fan outward when the bottom of their foot is stroked In contrast, motor skills are voluntary movements of the body. Over time, complex motor skills develop in a common, predictable order (eg, rolling over before sitting, sitting before standing). **Gross motor skills** involve large muscle movements (eg, waving an arm). **Fine motor skills** involve smaller muscle movements that allow a person to perform more precise actions (eg, pinching an object between the thumb and index finger). Gross motor skills develop before fine motor skills (eg, children can wave their arms before they can hold a crayon). By elementary school age (\~6 years), children can easily grasp and manipulate small items (eg, buttons) Lesson 7.1 **Neuroimaging Techniques** 7.1.01 Neuroimaging Techniques **Neuroimaging techniques** detect brain structure and/or function (see Table 7.1). Neuroimaging that detects *brain structure* reveals the size of brain areas and surrounding structures (eg, the fluid-filled ventricles of the brain), as well as any abnormalities in the tissue (eg, tumors). Techniques that are specialized for visualizing brain structures include: Computerized tomography (CT) or computerized axial tomography (CAT) generates images of the brain by combining x-ray images taken from different angles. [Magnetic resonance imaging](javascript:void(0)) (MRI) uses powerful magnets to create detailed images of the brain. MRI provides a closer and more precise image than a CT scan. Other neuroimaging techniques reveal *brain activity* and *functioning*. Techniques that are useful in assessing brain function include: [Positron emission tomography](javascript:void(0)) (PET) provides information about physiological activity in the brain by monitoring glucose metabolism. Active neurons consume glucose (sugar) for energy, and more active brain regions use more glucose. PET measures positively charged particles (positrons) that are emitted during the metabolism of a radioactive glucose tracer injected prior to the scan. [Functional magnetic resonance imaging](javascript:void(0)) (fMRI) is used to visualize brain activity by measuring changes in blood oxygen levels in the brain. Active brain areas require more oxygen and an increased blood supply. fMRI uses a powerful magnet to detect which areas of the brain require increased blood flow, indicating increased brain activity. [Electroencephalography](javascript:void(0)) (EEG) measures electrical brain activity through the use of electrodes attached to the scalp. Because action potentials involve a sequence of shifts in the electrical charge of the neural membrane, neural communication involves electrical activity. The readout from an EEG depicts waves of brain activity (eg, showing stages of sleep **Other Methods Used in Studying the Brain** 7.2.01 Other Methods Used in Studying the Brain In addition to [neuroimaging](javascript:void(0)) (see Lesson 7.1), scientists use a variety of other techniques in their study of the brain. **Electrical stimulation of the brain** (ESB) stimulates precise brain areas with an electric current. For example, stimulation of the region of the motor cortex in the left hemisphere that controls the hand would cause movement of the right hand. ESB has many applications; for instance, it can be used to determine the function of specific brain areas. Another technique, **lesioning**, involves destroying specific areas of the brain. Lesioning is a research tool used in studies with animals. For example, scientists could use lesioning to learn about the function of a brain area by determining what processes are disrupted as a result of damage to that area. Lesioning can also be used to treat movement disorders such as dystonia (ie, involuntary movement **Principles of Sensation** 8.1.01 Sensory Adaptation Sensation arises through the process of [transduction](javascript:void(0)). **Transduction** occurs when sensory receptors (eg, olfactory receptors) convert environmental stimuli (eg, a smell) into neural signals. The nervous system then relays that information to different areas of the brain for processing. **Sensory adaptation** occurs when the constant presence of a sensory stimulus causes sensory receptor cells to send fewer messages to the brain about that stimulus. In other words, when a stimulus does not change, the firing rate of the responding receptor declines. Sensory adaptation explains why, for example, an individual would initially detect a strong garbage odor but, after a few hours, be less able to detect the smell (see Figure 8.1). **Figure 8.1** Sensory adaptation example. 8.1.02 Psychophysics In the 1800s, Ernst Weber and Gustav Fechner studied how sensation could be altered by varying the intensity of a stimulus. **Ernst Weber** studied the **difference threshold**, also called the **just-noticeable difference** (JND), the point at which an individual can detect a difference between two stimuli (eg, the heaviness of two weights) 50% of the time (Figure 8.2). A diagram of a brain and a trash can Description automatically generated Chapter 8: Sensation 48 **Figure 8.2** Example of the difference threshold. As the intensity of the stimulus increases, the amount of change needed to detect a difference in that stimulus also increases. This relationship is quantified by **Weber\'s law**, which states that the proportion of the size of the JND to the original stimulus intensity is a constant: ∆ I I = k where Δ*I* is the size of the JND, *I* is the original stimulus intensity, and *k* is a proportionality constant. Once the JND has been determined for a particular stimulus intensity, it can be predicted for new stimulus intensities. For example, consider that a weight of 30 lb must be increased by 6 lb for an individual to notice a difference in heaviness between the two weights half the time. In this example, 6 lb 30 lb = 0.2 If a 40-lb weight is contrasted with progressively heavier weights, this formula will determine the lowest weight at which the individual can detect the increase. The new stimulus intensity for the weight is 40 lb, and the new JND can be calculated by ∆ I 40 lb = 0.2 ∆I = 8 lb Therefore, the 40-lb weight must be increased to 40 lb + 8 lb = 48 lb for a difference in heaviness to be detected.  Another scientist, **Gustav Fechner**, studied the **absolute threshold**, the point at which an individual can detect a new sensation (eg, see a light in the distance) 50% of the time. Figure 8.3 depicts common absolute thresholds. **Figure 8.3** Examples of the absolute threshold. The ability to correctly detect a stimulus is also impacted by the environment. **Signal detection theory** explores how judgments or decisions are made amid \"noise\" (external or internal distractions). Signal detection theory describes [four possible outcomes](javascript:void(0)). When a signal (eg, auditory tone) is correctly perceived as present, it is a correct detection, or a \"hit.\" When a signal is not detected even though it is present, it is a false negative, or a \"miss.\" When a signal is absent but a perception is erroneously reported, this is a false positive, and when the signal is accurately judged absent, it is a correct rejection Chapter 8: Sensation 50 Lesson 8.2 **Sensory Receptors** 8.2.01 Types of Sensory Receptors As Concept 8.1.01 describes, sensory receptors are responsible for transduction. **Sensory receptors** are specialized cells that detect stimuli in the internal (eg, blood pressure) or external (eg, light) environment and transmit this information to the nervous system. The major types of sensory receptors are mechanoreceptors, thermoreceptors, photoreceptors, and chemoreceptors. **Mechanoreceptors** are sensitive to mechanical stimulation caused by pressure, vibration, or movement. For example, auditory receptors are hair cells on the basilar membrane that bend in response to sound (see Figure 8.4). This movement causes the cells to depolarize, transmitting information to the brain. Other examples of mechanoreceptors include proprioceptors, vestibular receptors, and some somatosensory receptors. **Figure 8.4** Auditory transduction. Another type of receptor that can be found in the skin is **thermoreceptors**, which are sensitive to temperature. An example of a thermoreceptor is a receptor in the skin that responds to heat. In contrast, **photoreceptors** are sensitive to light. Rods and cones are the two main types of photoreceptors and they enable vision by converting light into neural impulses. **Chemoreceptors** are sensitive to chemicals and are the type of receptors involved in taste and [smell](javascript:void(0)). In these chemical senses, food and odor molecules chemically activate taste and olfactory receptors, respectively. See Table 8.1 for an overview of these sensory receptor types. **Table 8.1** Sensory receptors. **Detects** **Stimuli** **Example** **Mechanoreceptor** Movement Sound waves, touch Hair cells (ear) **Thermoreceptor** Temperature Heat, cold Free nerve endings (skin) **Photoreceptor** Light waves Visible light Rods, cones (retina) **Chemoreceptor** Chemicals Molecules, solutes Taste buds (tongue) 8.2.02 Sensory Pathways Most of the pathways that carry information from the various senses have a noteworthy commonality; information from those senses travels through the **thalamus** on the way to the cortex. For example, visual information is relayed through the thalamus\' lateral geniculate nucleus (LGN) on the way to the primary visual cortex. However, in [olfaction](javascript:void(0)), olfactory receptor neurons transmit smell information to the olfactory bulb. The olfactory bulb relays the information to other brain areas, such as the hippocampus and the amygdala. Although sensory information from all the other senses travels to the thalamus before further brain areas, olfactory information bypasses the thalamus and is instead sent directly to other structures. A diagram of a brain Description automatically generated **Principles of Perception** 9.1.01 Top-Down and Bottom-Up Processing Chapter 8 describes how sensory information is converted into neural signals. The process of **perception** involves integrating, organizing, and making meaning out of the data collected by the senses. Perception guided by preexisting information or beliefs is called **top-down processing** (also called conceptually driven processing). For example, an individual misperceives a garden hose as a coiled-up snake after hearing about a snake earlier in the day. A [perceptual set](javascript:void(0)) describes this tendency to focus on certain details of a stimulus while overlooking other details. Culture, experiences, mood, and expectations can influence one\'s perceptual set. For instance, when viewing a movie about the Revolutionary War, a theater major and a history major might focus on different aspects of the movie (eg, acting versus historical inaccuracies, respectively). In contrast, **bottom-up processing** (or stimulus-driven processing) occurs when perception is guided by the details of the sensory input. For example, an individual looks at shapes on a canvas and identifies them as animals. Top-down and bottom-up processing are contrasted in Figure 9.1. **Figure 9.1** Top-down versus bottom-up processing.  Chapter 9: Perception 53 9.1.02 Perceptual Organization Principles of **perceptual organization** (eg, form, constancy, depth, motion) are top-down cognitive processes wherein the brain\'s interpretation of sensory information is guided by expectation and prior experiences. Differing expectations can cause two individuals viewing the same image to perceive different objects. The perception of form is also guided by the Gestalt principles covered in Concept 9.1.03. The principle of **perceptual constancy** describes the tendency to perceive an object as unchanging despite slight changes to the object that occur while one is viewing it (eg, light or movement causing alterations to color, size, brightness, or shape; Figure 9.2). For instance, size constancy results in an object appearing to not change size despite changing distance (eg, a bird flying away does not appear to shrink). **Figure 9.2** Perceptual constancy. The ability to see in three dimensions is called **depth perception** and is enabled by the brain\'s interpretation of the two-dimensional information in the eye. Depth cues contribute to depth perception; monocular depth cues use information from just one eye, whereas binocular cues require both eyes. The **monocular depth cues** (Figure 9.3) include: Interposition is a cue wherein an object that is partially blocked by another object is perceived as farther away. Relative size is a cue wherein if an individual assumes two objects are a similar size, then the one that appears smaller is perceived as farther away. Relative height (sometimes called height in plane) is a cue wherein an object that is lower is perceived to be closer within the visual plane than higher objects. Motion parallax (sometimes called relative motion) results in nearer objects appearing to pass more quickly than farther objects while the observer is moving. Linear perspective results in parallel lines (eg, train tracks) appearing to come together in the distance. A collage of different types of objects Description automatically generated Chapter 9: Perception 54 **Figure 9.3** Monocular depth cues. In contrast, the **binocular depth cues** contribute to depth perception through the integration of slightly different information from the left and right eyes. Binocular depth cues (Figure 9.4) include: **Retinal disparity** describes how the brain judges the distance of an object based on the difference between the visual information from each retina. **Convergence** describes how the eyes move together (ie, converge) to view a close object and the brain interprets the degree of convergence as an indication of the object\'s distance. **Figure 9.4** Binocular depth cues.  A diagram of a brain and a book Description automatically generated Chapter 9: Perception 55 Visual principles of perceptual organization help explain why perceptual illusions occur. These principles allow the brain to use mental shortcuts to process visual information more quickly, which can enable optical illusions. For example, the **phi phenomenon** describes how adjacent flashing lights create the perception of motion (ie, the lights appear to move). 9.1.03 Gestalt Principles The **Gestalt principles** of perceptual organization describe how humans perceive sensory stimuli as a whole greater than the sum of their parts. Gestalt principles apply to many types of sensory stimuli (eg, the grouping of musical tones) but are most often used to describe the perception of visual stimuli. Examples of Gestalt principles (Figure 9.5) include: Subjective contours (or illusory contours) is the tendency to perceive the contours (ie, edges) of a shape even though they are not fully depicted. Similarity is the tendency to group together objects that share similar features (eg, shape, color). Continuity (or good continuation) is the tendency to perceive elements as continuing on a smooth path (eg, \"X\" is perceived as two crossing lines rather than two \"V\" shapes touching). Figure-ground refers to the tendency to perceive objects (ie, figures) as distinct from a background (ie, the ground). Closure is the tendency to perceive a whole object by filling in gaps. Proximity is the tendency to perceive things that are physically closer to one another as a group (eg, letters that are closer together are grouped as a word). **Figure 9.5** Examples of Gestalt principles.