science

Simultaneous action selection

Simultaneous action selection is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Simultaneous action selection rather than just read about it. In short: Simultaneous action selection, or SAS, is a game mechanic that occurs when players of a game take action (such as moving their pieces) at the same time. Examples of games that use this type of movement include rock–paper–scissors and Diplomacy.

Key takeaways

Simultaneous action selection belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Simultaneous action selection to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Simultaneous action selection from memory before moving on to harder problems.

Reference excerpt

Simultaneous action selection, or SAS, is a game mechanic that occurs when players of a game take action (such as moving their pieces) at the same time. Examples of games that use this type of movement include rock–paper–scissors and Diplomacy. Typically, a "secret yet binding" method of committing to one's move is necessary, so that as players' moves are revealed and implemented, others do not change their moves in light of the new information. In Diplomacy, players write down their moves and then reveal them simultaneously. Because no player gets the first move, this potentially arbitrary source of advantage is not present. It is also possible for simultaneous movement games to proceed relatively quickly, because players are acting at the same time, rather than waiting for their turn. Simultaneous action selection is easily implemented in card games such as Apples to Apples in which players simply select cards and throw them face-down into the center.

Limitations Some games do not lend themselves to simultaneous movement, because one player's move may be prevented by the other player's. For instance, in chess, a move of a bishop takes queen would be incompatible with a simultaneous opposing move of queen takes bishop. By contrast, simultaneous movement is possible in Junta because each coup phase has a movement stage and a separate combat stage; no units are removed until all have had a chance to move. It has been noted that "a certain amount of reverse psychology and reverse-reverse psychology ensues" as players attempt to calculate the implications of others' potential actions. Junta also has simultaneous action selection in that players secretly choose their locations at the same time. This is important in that, for instance, a player plotting an assassination may choose the bank for his or her own location (hoping to quickly deposit the ill-gotten gains) before finding out whether the location of his or her assassination was on the mark.

Real world applications Simultaneous action selection is used in many real-world applications such as first-price sealed-bid auctions. The fact that no bidder knows what others are planning to bid may provide an incentive to bid high if there is a strong desire to win the auction, which can result in much higher winning bids than if better information were available. The prisoner's dilemma is another classic example of simultaneous action selection. SAS can also be used to introduce an element of chance, as when rock–paper–scissors is used to decide a matter.

See also First-move advantage in chess – Advantage of White over Black in chess Real-time strategy – Strategy video game sub-genrePages displaying short descriptions of redirect targets Simultaneous game – Game class in game theory

References

External links BoardGameGeek: Games using simultaneous action selection BoardGameGeek wiki: Simultaneous Action Selection

Illustrations

Worked examples

Example 1 — a first encounter with Simultaneous action selection

Start with the simplest possible case. Write down what Simultaneous action selection claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Simultaneous action selection before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Simultaneous action selection ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Simultaneous action selection

In research: Simultaneous action selection appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Simultaneous action selection in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Simultaneous action selection is common in secondary-school and first-year university syllabi. It links to neighbouring topics Game design, Game theory, so understanding it makes those chapters shorter.
In everyday life: Look for Simultaneous action selection outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Simultaneous action selection in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Simultaneous action selection means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Simultaneous action selection out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Simultaneous action selection in simple terms?

Why does Simultaneous action selection matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Simultaneous action selection?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Simultaneous action selection.