5) Depressive Phenotypes

why would interruption cause Darwin to forget what he was thinking about?

he had to keep a lot of unrelated facts in his head at the same time

Working Memory

Definition: Keeps information active during ongoing mental tasks.

Darwin needed WM to connect complex ideas — like eye evolution in mollusks.

• Had to recall details, compare species, and synthesize insights.

• Interruptions caused forgetting — showing WM’s fragile, high-demand nature.

2 types of thinking styles

type 1:

• fast, automatic, ituitive

• uses heuristics

• low effort, often error prone

• evolutionaryily impact

type 2:

• slow, analytical, deliberate

• uses working memory

• high effort, attention-demanding

• energentically expensive

what was darwin’s thinking style?

Analytical (Type 2) — breaking big problems into smaller ones. - divide and conqcure
→ Required sustained WM and emotional focus.
→ Sad or depressed mood promotes analytical thinking.

depressive phenotypes

sickenss behaviour - Conserves energy for immune response.

• ahedoinna p loss in interst in sex and food → promotes eergy reallocation to immune system in tead of sogntiio soical asn phsycail aocotut, gowth, etc

• more fagiuge, less cognitve effort

• eat more carbs nad less iron foods

• sleep more, less REM sleep

• increase core body temp

• Insulin resistance (IR) redirects glucose to immune tissues.

starvation depression - Prioritize brain and foraging over reproduction or immunity.

• Anhedonia: lost interest in sex/humor, but not food

• Fatigue: rest more but still forage actively

• Eat less: prefer protein

• Low core temp

• Weakened immunity

🧠 Adaptive purpose: Prioritize brain and foraging over reproduction or immunity.

• Energy reallocated to brain (hypothalamus, mesolimbic reward system).

• Insulin sensitivity (IS) increases in brain → fuels foraging cognition.

• IR in muscle = energy saving.

Melancholia - deep though

• Anhedonia: loss of interest in food/sex, but ↑ interest in thoughts

• Sleep less: more REM (memory consolidation)

• Fever-like body temp

• High cortisol (HPA axis activation)

• Shift from social/physical activity → cognitive focus.
  → Promotes rumination (deep analytical thought). - persistant distractino-resistant thoughts

How energy is re-directed to immune tissues

during sickness

Insulin sensitivity (IS) and insulin resistance (IR) reflect how easily glucose (sugar) is taken from the bloodstream. Changes in IS/IR reflect the body’s adaptive metabolic response to (in this case) sickness. Starvation

Insulin resistance helps reallocate energy as the situation demands!