AP Psychology Flashcards: Sensation and Perception, Vision, Hearing, Gestalt Principles

Sensation is the process by which sensory receptors detect physical energy from the environment and convert it into neural signals, a process called transduction. Perception is the brain's interpretation and organization of those sensory signals into meaningful experiences. Sensation is bottom-up processing, driven by raw sensory data. Perception involves top-down processing, where expectations, knowledge, and context shape interpretation. For example, sensation detects sound waves hitting the eardrum, while perception interprets those sounds as a familiar song.

The absolute threshold is the minimum amount of stimulation needed to detect a stimulus 50 percent of the time, such as the faintest sound a person can hear in a quiet room. The difference threshold, also called the just noticeable difference, is the minimum change in stimulation needed to detect a difference between two stimuli 50 percent of the time. Weber's law states that the difference threshold is a constant proportion of the original stimulus: a heavier object requires a larger change in weight to notice a difference than a lighter one.

The Gestalt principles describe how the brain naturally groups visual elements into organized patterns. Proximity groups nearby elements together. Similarity groups elements that look alike. Closure fills in gaps to perceive complete shapes from incomplete information. Continuity perceives smooth, continuous patterns rather than abrupt changes. Figure-ground separates the main object from the background. Common fate groups elements that move in the same direction.

Light enters the eye through the cornea and pupil, is focused by the lens onto the retina at the back of the eye. The retina contains two types of photoreceptors: rods, which are sensitive to low light and detect black, white, and gray for night vision, and cones, which operate in bright light and detect color and fine detail. The fovea, the central point of the retina, contains the highest concentration of cones for sharp central vision.

The trichromatic theory, proposed by Young and Helmholtz, states that the retina contains three types of cones sensitive to red, green, and blue light, and all other colors are perceived through combinations of these three. This explains color mixing and certain types of color blindness. The opponent-process theory, proposed by Hering, states that color is processed in opposing pairs: red versus green, blue versus yellow, and black versus white. This explains afterimages and why we never see reddish-green or bluish-yellow.

Binocular depth cues require both eyes. Retinal disparity is the slight difference between images each eye receives because of their different positions, which the brain uses to judge distance. Convergence is the inward turning of eyes for near objects. Monocular depth cues work with one eye. Relative size assumes smaller images are farther away. Interposition or overlap means a closer object blocks a farther one. Linear perspective shows parallel lines converging in the distance. Texture gradient shows finer texture at greater distances.

Sound waves enter the outer ear and travel down the ear canal to the tympanic membrane, or eardrum, causing it to vibrate. These vibrations pass through three tiny bones in the middle ear called the hammer, anvil, and stirrup, which amplify the sound. The stirrup pushes against the oval window of the cochlea in the inner ear, creating waves in the fluid-filled chamber. Hair cells along the basilar membrane inside the cochlea bend in response to these waves and convert the mechanical energy into neural signals. ---