Era 02 / 15 · The Turing Era 1936–1950

Can a Machine Think?

Computation got a precise definition, and “can it think?” got a test.

Beat 1 · Concrete

A head, a tape, a rule

All of computing, stripped bare: read a symbol, write a symbol, step. Here it adds one.

A Turing machine incrementing a binary number A read/write head moves along a tape of cells holding the binary number 23. Reading a 1 it writes 0 and steps left; reading a 0 it writes 1 and halts, leaving 24. 0 0 1 0 1 1 1 … … TAPE R/W RULE TABLE read 1 → write 0, step ◄ left read 0 → write 1, halt READ → WRITE → STEP

23 → 24 · the head's motion is the arithmetic

Beat 2 · Abstract

The imitation game

A judge questions two hidden voices — one human, one machine — and must tell which is which.

The imitation game A judge on the left sends a question across a curtain to two hidden respondents on the right, a human and a machine. Both send replies back. The judge must guess which reply came from the machine. ? JUDGE which is the machine? question → ← two answers CURTAIN ? voice A ? voice B ① question ② two answers ③ a guess

identity is hidden — only the words cross the curtain

Beat 3 · Interactive

Which is the machine?

Two replies, one written by a machine trying to pass. Click the one you suspect.

—

Round 1 of 3 · spotted 0

Click the reply you think a machine wrote.

“Add 34957 and 70764.”

Reply A
“Let me see… (pause) 105621.”
Reply B
“Around 105,700 — honestly I'd reach for a calculator.”

Reveal: A was the machine. In Turing's own 1950 example it pauses and answers slightly wrong — playing dumb to seem human.

a correct guess = you saw through the imitation

Footnotes · three turning points
1936
On Computable Numbers
Turing defines computation with an abstract machine — and proves the halting problem: no procedure can decide, for every program, whether it will ever stop.
Universal
The universal machine
One machine can read another's rule table from its tape and run it. Software as data — the seed of every stored-program computer.
1950
Computing Machinery & Intelligence
Turing replaces “can machines think?” with a game you can actually run: if a judge can't tell machine from human by conversation, the question dissolves.