Research ArticlePSYCHOLOGICAL SCIENCE

Recursive sequence generation in monkeys, children, U.S. adults, and native Amazonians

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Science Advances  26 Jun 2020:
Vol. 6, no. 26, eaaz1002
DOI: 10.1126/sciadv.aaz1002
  • Fig. 1 Task design and stimuli.

    (A) Monkeys, children, U.S. adults, and Tsimane’ adults complete the sequence generation task. Subjects were required to touch the images in a center-embedded order. (B) A sample training trial is shown. Subjects were trained to order two training lists in which the pictures had to be touched in a specific center-embedded order (C) and were tested on a third transfer list that was rewarded regardless of the sequence generated (D). Photo credit: S.F., Harvard University.

  • Fig. 2 The proportion of center-embedded, crossed, and tail-embedded responses on transfer trials for monkeys, children, U.S. adults, and Tsimane’ adults.

    Error bars represent the SE of the proportion. ns, not significant. * represents a significant difference (P < 0.05) between center-embedded responses and crossed responses using a two-tailed binomial test.

  • Fig. 3 With additional exposure, monkeys show generalization performance similar to that of children.

    (A) The proportion of center-embedded, crossed, and tail-embedded responses for monkeys on transfer trials after training on two additional lists. (B) A comparison between the average performance of children on the first exposure and individual monkeys tested after the additional training. Error bars represent the SE of the proportion. * represents a significant difference (P < 0.05) between center-embedded responses and crossed responses using a two-tailed binomial test.

  • Fig. 4 The proportion of center-embedded, crossed, and tail-embedded responses for monkeys on the generalization to novel lists.

    Error bars represent the SE of the proportion. * represents a significant difference (P < 0.05) between center-embedded responses and crossed responses using a two-tailed binomial test.

  • Fig. 5 The probability of using a recursive strategy for each group (red) and each individual in that group (black), using a Bayesian data analysis that allowed strategies to vary by individual and population.

    The dotted line represents the prior. Error bars around the group means represent the 95% credible interval.

  • Fig. 6 The effects of noise and memory errors on generating center-embedded structures.

    (A) The probability each group made an error implementing their strategy at least once in a trial, according to the results of the Bayesian analysis. (B) The probability each group generates center-embedded responses, with noise included in the model (light gray) and excluded from it (dark gray). The red bars represent the difference in center-embedding rates with and without noise for each group (i.e., the difference in the height of the bars). The error bars around the means in both (A) and (B) represent the 95% credible intervals. (C) Working memory performance, as measured by a forwards-digit task, was correlated with the proportion of center-embedded responses. (D) Age was not correlated with the proportion of center-embedded responses. The shaded regions represent 95% confidence intervals in (C) and (D).

Supplementary Materials

  • Supplementary Materials

    Recursive sequence generation in monkeys, children, U.S. adults, and native Amazonians

    Stephen Ferrigno, Samuel J. Cheyette, Steven T. Piantadosi, Jessica F. Cantlon

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    The PDF file includes:

    • Supplementary Materials and Methods
    • Supplementary Results
    • Figs. S1 to S9
    • Legend for movie S1
    • References

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