psych 9a // chapter 4

• Sensation is the process by which one’s sensory organs receive stimulus energies from the environment.
• Transduction is the transformation of sensory stimulus energy from the environment into neural impulses.
• Perception is the neural processing of electrical signals to form an internal mental representation inside one’s brain of what’s on the outside.
• Dark adaptation is the process by which the eyes adjust to low levels of light by becoming more sensitive to dimly lit environments.
• Adaptation is a phenomenon whereby an individual stops noticing a stimulus that remains constant over time, resulting in enhanced detection of stimulus changes.
• Sensory adaptation refers to changes in the sensitivity of sensory receptors in response to prolonged or constant stimulation.
• Perceptual adaptation refers to changes in the interpretation and organization of sensory information by the brain, leading to alterations in perceptive and subjective experience.
• Aftereffects are a phenomenon in which temporary opposing distortions occur as a result of adaptation.
• Reduced adaptation is a central aspect of autism, which is a neurodevelopmental disorder characterized by altered communication skills and repetitive behaviors.
• Psychophysics is the study of the relationship between the physical characteristics of environmental stimuli and the mental experience of those stimuli.
• An absolute threshold is the minimum amount of stimulation necessary for someone to detect a stimulus half of the time.
• Signal detection theory is an approach to measuring thresholds that takes into account both the intensity of the stimulus and psychological biases for a more accurate assessment.
• Signal detection theory takes into account hits (responding “yes” when a stimulus is present) and misses (responding “no” when a stimulus is present), but also false alarms (responding “yes” when no stimulus is present) and correct rejections (responding “no” when no stimulus is present).
• A difference threshold is the minimum difference required between two stimuli for an observer to detect a difference half of the time; also known as just-noticeable difference (JND).
• Weber's law is the observation that the likelihood of perceiving a stimulus change is proportional to the magnitude of the stimuli.
• Wavelength refers to the distance between two consecutive crests or troughs of a wave.
• Frequency refers to the number of cycles per second of a wave.
• Wavelength is visually perceived as hue and is related to frequency, such that longer-wavelength light has lower frequency and vice versa.
• Amplitude refers to the height of the crests of a wave.
• Amplitude is visually perceived as intensity or brightness.
• The pupil is a hole in the iris where light enters the eye.
• The iris is the colored muscle circling the pupil.
• The lens is a membrane at the front of the eye that focuses the incoming light on the retina.
• Accommodation refers to the adjustment of the lens’ thickness by specialized muscles in order to change the degree to which it bends light
• The retina is a surface on the back of the eye that contains the photoreceptor cells.
• Rods are photoreceptor cells that primarily support nighttime vision.
• Cones are photoreceptor cells that are responsible for high-resolution color vision.
• The photoreceptor cells contain photopigments, which are sensitive to light and can pick up different wavelengths of light and convert them into electrical signals.
• To travel to the brain, action potentials from the retina converge in a bundle of axons called the optic nerve.
• The blind spot is an area in the middle of the visual field where there are no photoreceptors and no information can be received.
• The cones are most densely clustered in the fovea, which is a small pit in the center of the retina.
• Foveation is the process of directing the center of gaze, or the fovea, toward a specific object or point of interest in the visual field.
• Cones specialize in acuity, which is the sharpness or specificity of perception, while the rods provide more sensitivity, which is the ability to simply detect that a stimulus is present.
• All sensory systems have a systematic distortion, called a cortical magnification factor, whereby regions that require finer discrimination receive more cortical representation.
• Trichromatic theory is a theory of color perception stating that three types of cone cells, each most sensitive to a specific wavelength of light, work together to produce the perception of a multicolored world.
• Colorblindness is a condition in which an individual has difficulty distinguishing certain colors or perceiving colors accurately.
• Dichromacy is a specific type of colorblindness in which an individual has only two types of functioning cones in the retina, resulting in the difficulty to distinguish two types of colors, such as red and green.
• Monochromacy is a specific type of colorblindness in which an individual has only one type of functioning cone in the retina, resulting in the inability to perceive colors at all.
• The Purkinje shift is the phenomenon in which the sensitivity of the human visual system to different colors shifts depending on the level of light.
• Opponent-process theory is a theory of color perception stating that information from the cones is separated into three sets of opposing, or opponent, channels in the ganglion cell layer.