Punctuation Junction: Parentheses and Brackets

by Chelsea Lee

Punctuation Junction: A series about what happens when punctuation marks collide.

Parentheses and brackets are used to enclose and set off material from the main text. Although writers usually need only one set of parentheses or brackets at a time, for more complex material they may need an enclosure within an enclosure (referred to as a double enclosure in this post).

Four guidelines govern how to use these punctuation marks together (or not) to handle double enclosures in an APA Style paper.

1. Use brackets inside parentheses to create a double enclosure in the text. Avoid parentheses within parentheses, or nested parentheses.

• Correct: (We also administered the Beck Depression Inventory [BDI; Beck, Steer, & Garbin, 1988], but those results are not reported here.)
• Incorrect: (We also administered the Beck Depression Inventory (BDI; Beck, Steer, & Garbin, 1988), but those results are not reported here.)

2. Separate citations from parenthetical text with either semicolons (for parenthetical-style citations) or commas around the year (for narrative citations). Do not use a double enclosure or back-to-back parentheses.

• Correct: Gender differences may reflect underlying continuous attributes, such as personality (e.g., communion and agency; Spence & Helmreich, 1978). These distinctions are reflected in sexually dimorphic brain structures (see Ellis et al., 2008, for recent meta-analyses).
• Incorrect: Gender differences may reflect underlying continuous attributes, such as personality (e.g., communion and agency) (Spence & Helmreich, 1978). These distinctions are reflected in sexually dimorphic brain structures (see Ellis et al. [2008] for recent meta-analyses).

3. When a mathematical equation contains one level of enclosure, use parentheses, ( ); for two levels, add brackets outside, [( )]; for three levels, add curly brackets outside, {[( )]}.

• Correct: Participants were asked to solve the following math problem for x after completing the priming measures: 8[x + 4(2x + 1)] = 248
• Incorrect: Participants were asked to solve the following math problem for x after completing the priming measures: 8(x + 4[2x + 1]) = 248

4. Avoid adding a level of enclosure to statistics that already contain parentheses. Instead, use commas to set off the statistics from the text.

• Correct: The results were statistically significant, F(1, 32) = 4.37, p = .045.
• Incorrect: The results were statistically significant (F[1, 32] = 4.37, p = .045).
• Incorrect: The results were statistically significant [F(1, 32) = 4.37, p = .045].

For more on how these punctuation  marks are used, see Publication Manual §4.09, §4.10, and §4.47. Keep an eye out for more Punctuation Junction posts coming soon!

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Example text in Guideline 2 adapted from “Men and Women Are From Earth: Examining the Latent Structure of Gender,” by B. J. Carothers and H. T. Reis, 2013, Journal of Personality and Social Psychology, 104, p. 386. Copyright 2013 by the American Psychological Association.