Foundations of Psychology

Psychology became a science when it began testing claims about the mind and behavior against controlled, repeatable evidence instead of settling them by argument.

A controlled experiment isolates a cause by manipulating one independent variable under random assignment while holding everything else constant, which is why correlation alone can never establish causation.

Research on people is bound by informed consent, minimized harm, the right to withdraw, and debriefing — the ethical frame that makes studies like Milgram's unrepeatable today.

A neuron carries information as an all-or-none electrical impulse and passes it to the next cell by releasing neurotransmitters across the synaptic gap.

Because injury to a specific brain region produces a specific loss, case and lesion studies reveal what each region does.

A perceived threat triggers a fast fight-or-flight reaction and a slower hormonal cascade along the HPA axis — adaptive in short bursts, damaging when the alarm never shuts off.

Perception is not a recording of the world but an active construction the brain assembles from incomplete sensory signals and prior expectations, which is why attention can make an obvious event invisible.

Memory runs in three acts — encoding, storage, retrieval — and what we keep decays along Ebbinghaus's steep-then-slow curve while quietly reshaping itself rather than replaying intact.

A heuristic is a fast rule of thumb that usually reaches a good-enough judgment but misfires in predictable ways.

In classical conditioning, a neutral signal that reliably comes before an automatic response starts to trigger that response on its own.

In operant conditioning, behavior is shaped by its consequences, and the schedule of reward controls how fast and how stubbornly the behavior persists.

Emotion combines bodily arousal with an interpretation of that arousal, and motivation is driven by internal drives, external incentives, and intrinsic interest together.

Minds develop in a partly ordered sequence — from infant attachment through Piaget's stages of reasoning — and keep changing, gaining and losing different capacities, into old age.

Personality can be described by a small set of stable trait dimensions — the Big Five — yet behavior always answers partly to the situation, not to traits alone.

A pattern counts as a disorder when it brings lasting distress or dysfunction, and the major therapies work by changing thoughts, behaviors, or brain chemistry — each with its own evidence.

People systematically underweight circumstance when explaining others — the fundamental attribution error — even though Asch's conformity and Milgram's obedience studies show how strongly the situation drives what people do.