The four temperaments originate in Ancient Greek medicine.
Hippocrates (5th century BCE) proposed that health and personality are governed by four bodily fluids or “humors.”
Later, Galen (2nd century CE) systematized this theory and linked the humors to psychological traits.
Each temperament was thought to result from an excess of one humor: blood, yellow bile, black bile, or phlegm.
Though outdated medically, the four types—Sanguine, Choleric, Melancholic, and Phlegmatic—remain influential in personality theory.
Element: Earth Qualities: Cold and dry Humor: Black bile
Personality: Thoughtful, introspective, detail-oriented, serious
Behavior: Prone to sadness, perfectionistic, loyal, needs solitude, deep thinker
Modern comparison: Introverted and analytical
Element: Air
Qualities: Warm and moist
Personality: Social, energetic, talkative, lively, optimistic
Behavior: Enjoys people, easily distracted, creative, forgets obligations
Modern comparison: Extroverted and emotionally expressive
Element: Fire Qualities: Warm and dry Humor: Yellow bile
Personality: Ambitious, leader-like, passionate, easily angered
Behavior: Goal-oriented, confident, aggressive, impatient, not easily discouraged
Modern comparison: Assertive, dominant, sometimes aggressive
1. Energy Direction (E or I):
E = I gain energy from being active, social, or in groups.
I = I gain energy from being alone, quiet, or reflective.
2. Response Style (F or A):
F = I react quickly, outwardly, and emotionally.
A = I stay calm, take time, and keep emotions inside.
Element: Water Qualities: Cold and moist Humor: Phlegm
Personality: Calm, kind, peaceful, reliable
Behavior: Avoids conflict, patient, compassionate, steady, sometimes passive
Modern comparison: Relaxed and agreeable
Renewed interest in Platonism and Hermetic soul cosmologies.
Descartes: radical dualism—soul (res cogitans) and body (res extensa).
Human soul seen as seat of reason, will, and self-consciousness.
Debates emerge over animal souls and mechanistic bodies.
Mystical and esoteric views on soul persisted alongside rationalism.
Soul increasingly tied to the concept of personhood.
Soul increasingly reduced to observable mental or bodily processes.
Locke: denies innate ideas—soul as tabula rasa, a passive receiver. Start of the NATURE / NURTURE debate.
Hume: rejects a persistent self; mind is a bundle of perceptions.
La Mettrie: human soul is an effect of bodily mechanisms (*L'homme machine*).
Diderot and French materialists view soul as an illusion of matter in motion.
Mind-body dualism increasingly replaced by monist materialism.
Soul or mind functions through the association of ideas.
David Hartley: vibrations in nerves correspond to mental associations.
Mind explained through natural laws, not metaphysical substances.
Emphasizes memory, habit, and experience over rational soul.
Bridge between empiricism and early psychology.
Shift from soul as essence to mind as structure of learned relations.
Franz Joseph Gall proposed that mental faculties were localized in the brain.
Bumps on the skull supposedly indicated personality traits.
Phrenology gained popular appeal in 19th-century Europe and America.
Although flawed, it encouraged anatomical and neurological research.
Foreshadowed modern brain imaging and cognitive neuroscience.
Gustav Fechner studied the quantitative relationship between stimulus and sensation.
"psycho-physics is an exact doctrine of the relation of function or dependence between body and soul" (Elemente der Psychophysik, 1860)
His law: sensation increases logarithmically with stimulus intensity.
Considered one of the founders of experimental psychology.
Merged philosophy and empirical science through measurement.
Inspired later studies of perception and thresholds.
Hermann Ebbinghaus pioneered systematic study of memory.
Used nonsense syllables to avoid prior associations.
Identified the forgetting curve and spacing effect.
Demonstrated that memory could be studied experimentally and quantitatively.
His methods set standards for future cognitive research.
Describes how information is lost over time when there is no attempt to retain it.
The curve shows a steep drop in memory shortly after learning, then a slower decline.
After about 20 minutes, around 40% of new information is forgotten.
After one day, more than 60% can be lost without review.
The curve flattens over time—what is retained tends to stay longer.
Regular review or reinforcement can drastically reduce forgetting.
Discovered by Hermann Ebbinghaus and later formalized by modern memory researchers.
Describes how the position of an item in a sequence affects its likelihood of being recalled.
Primacy effect: early items are remembered better due to more rehearsal time.
Recency effect: late items are remembered better because they are still in short-term memory.
Items in the middle are most likely to be forgotten.
This effect creates a U-shaped curve when recall probability is plotted against position.