Sensation & Perception | AP Psychology

Sensation vs. Perception

• Sensation is the reception of external stimuli; perception is the organization and interpretation of that sensory information.

Absolute Threshold

• Defined as the minimum stimulation required to detect a stimulus 50% of the time.
• Example: Requires at least 2 inches of cut for noticeable change in shirt length.

Difference Threshold

• The minimum difference between two stimuli necessary for detection 50% of the time, referred to as the just noticeable difference (jnd).

Weber's Law

• States that to differentiate two stimuli, they must differ by a constant minimum percentage, not a constant amount.

Sensory Adaptation

• Diminished sensitivity to constant stimulation due to decreased nerve cell firing frequency over time.

Benefits of Sensory Adaptation

• Allows focus on changing stimuli in the environment, filtering out constant background noise.
• Example: Individuals may not notice their own scent due to adaptation.

Eye Movements and Sensory Adaptation

• Continuous eye movements ensure stimulation on the eyes' receptors changes, preventing sensory adaptation to visuals.

Visual Stimulation

• Eyes convert light energy into neural messages for the brain to process as conscious sight.

Stimulus Input

• Perception of color (e.g., red) arises from electromagnetic energy, not the color itself.
• Visible light represents only a small part of the entire electromagnetic spectrum.

Rods

• Retinal receptors responsible for detecting shades of black, white, and gray, critical for peripheral and dim-light vision.

Cones

• Retinal receptors functioning optimally in well-lit conditions, allowing for color perception and fine detail detection.

Bipolar Cells

• Specialized cells connecting rods and cones to the ganglion cells of the optic nerve.

Ganglion Cells

• Cells located behind bipolar cells; their axons create the optic nerve that transmits visual information to the brain.

Blind Spot

• The area where the optic nerve exits the eye contains no receptor cells, resulting in a visual gap.

Young-Helmholtz Theory

• Proposes three types of color receptors in the retina (red, green, blue) that combine to create the perception of any color.

Opponent-Process Theory

• Suggests color vision results from opposing retinal processes (red-green, yellow-blue, white-black) that allow for color differentiation.

Afterimage

• Visual sensations that persist after the stimulus is removed; common visual afterimages are often in inverted colors.

Color Constancy

• The ability to perceive familiar objects as maintaining consistent color, despite illumination changes altering reflected wavelengths.

Selective Attention in Perception

• Relates to the process where the brain focuses on specific stimuli while filtering out others, influenced by knowledge and expectations, shaping overall perception.