Our knowledge of the world around us is constructed through three highly interrelated cognitive processes: sensation, attention, and perception. Together, these processes form the basis of cognition, allowing us to gather information from both external and internal environments and interpret it meaningfully.
The environment contains a wide variety of stimuli that activate our specialized sense organs. Human beings possess seven sensory systems, categorized into five external senses and two deep internal senses:
Our sense organs function within biological limits. The scientific study of the relationship between physical stimuli and the sensations they evoke is called psychophysics.
Attention is the cognitive process of selecting a limited number of stimuli from a larger pool of environmental inputs. It involves properties such as alertness, concentration, and active search.
| Theory | Developer | Core Mechanism |
|---|---|---|
| Filter Theory | Broadbent (1956) | Stimuli enter a bottleneck where a selective filter allows only one input to pass for higher-level processing, screening out the rest. |
| Filter-Attenuation Theory | Treisman (1962) | Unselected stimuli are not completely blocked but are weakened (attenuated), allowing personally relevant cues (e.g., one's name) to slip through. |
| Multimode Theory | Johnston & Heinz (1978) | Attention is a flexible system operating across three stages (sensory, semantic, and conscious representation), with later stages requiring more mental effort. |
The span of attention refers to the amount of information an observer can grasp in a single brief exposure. Using a tachistoscope, researchers established that the human attentional span is limited to the "magic number" $7 \pm 2$ items.
When attentional mechanisms are disrupted, individuals may exhibit Attention Deficit Hyperactivity Disorder (ADHD), a behavioral disorder characterized by impulsivity, excessive motor activity, and an inability to sustain attention.
Perception is the process by which we recognize, interpret, and give meaning to sensory information. It is an active construction of reality influenced by our past experiences, motivations, and cultural backgrounds.
Perception is highly subjective and shaped by several internal factors:
Developed by Gestalt Psychology (Köhler, Koffka, and Wertheimer), these principles state that we perceive stimuli as organized, meaningful wholes rather than discrete sensory elements. The brain naturally seeks a "good figure" or pragnanz.
The most basic form of organization where we distinguish a prominent object (the figure) from its background (the ground). Figures have clear contours and appear closer, while the ground is relatively formless and recedes behind the figure.
Although retinal images are flat and two-dimensional, we perceive the world in three dimensions using depth perception, which relies on two types of cues.
Cues that require only one eye to perceive depth and distance:
Cues that require the coordinated use of both eyes:
The tendency to perceive objects as stable and unchanging despite variations in the sensory patterns projected onto our retinas:
Misperceptions resulting from the misinterpretation of sensory information. They are often called "primitive organizations" because they are experienced similarly by most people.
Experiment Title: Cross-Cultural Susceptibility to Illusions
Background/Subject: Comparative study by Segall, Campbell, and Herskovits involving subjects from remote African villages and Western urban settings.
Method/Procedure: Subjects from different environments were tested on their susceptibility to the Muller-Lyer and Vertical-Horizontal illusions.
Observations/Results: African subjects living in dense forests showed greater susceptibility to the vertical-horizontal illusion due to their regular experience with verticality (e.g., tall trees). Western subjects living in "carpentered" environments characterized by right angles showed greater susceptibility to the Muller-Lyer illusion.
Psychological Inference: Perceptual habits and susceptibility to illusions are learned and shaped by the physical and cultural environments in which individuals live.