Electronic Supplemental Material (ESM) for “Imitation is necessary for cumulative cultural evolution in an unfamiliar, opaque task”

Human Nature 25(1), doi: 10.1007/s12110-014-9192-5

Helen Wasielewski, Rutgers University, Email: helen.wasielewski@rutgers.edu

ContentsESM 1: Measures of success of clay and reed devices across generations....................................1

ESM 2: Summary of device performance per generation.................................................................31

ESM 3: Examples of devices................................................................................................................32

ESM 4: Cultural accumulation results for groups of size 3-10: Page’s L trend test.......................33

ESM 1: Measures of success of clay and reed devices across generations, for every group in the dataset.

Created in MS Word with graphs imported from SPSS

Groups of Ten, Asocial Condition:

1

Groups of Ten, End-product Condition:

2

Groups of Ten, Action Condition:

3

Groups of Ten, End-product and Action Condition:

4

Groups of Nine, End-product Condition:

Groups of Nine, Action Condition:

5

Groups of Nine, End-product and Action Condition:

6

Groups of Eight, End-product Condition:

7

Groups of Eight, Action Condition

8

Groups of Eight, End-product and Action Condition:

9

Groups of Seven, Asocial Condition:

10

Groups of Seven, End-product Condition:

11

Groups of Seven, Action Condition:

12

Groups of Seven, End-product and Action Condition:

13

Groups of Six, Asocial Condition:

14

Groups of Six, Asocial Condition, Continued:

15

Groups of Six, End-product Condition:

16

Groups of Six, Action Condition:

17

Groups of Six, End-product and Action Condition:

18

Groups of Five, Asocial Condition:

19

Groups of Five, End-product Condition:

20

Groups of Five, Action Condition:

Groups of Five, End-product and Action Condition:

21

Groups of Four, Asocial Condition:

22

Groups of Four, End-product Condition:

23

Groups of Four, Action Condition:

24

Groups of Four, End-product and Action Condition:

25

Groups of Three, Asocial Condition:

26

Groups of Three, End-product Condition:

Groups of Three, End-product and Action Condition:

27

Groups of Two, Asocial Condition:

Groups of Two, Action Condition:

28

Groups of Two, End-product and Action Condition:

29

Groups of One, Asocial Condition:

30

Position in Chain Position in Chain

Position in Chain

Position in Chain

Position in Chain

ESM 2: Summary of device performance per generation

The n-values indicate where the chain has been truncated.

Mean Number of Weights Held by Device

ConditionReplicates and Group size

First Generation (Position 1)M (SD)

Second Generation(Position 2)M (SD)

Third Generation(Position 3)M (SD)

Fourth Generation(Position 4)M (SD)

Fifth Generation (Position 5)M (SD)

LastGeneration (Positions 6 -10)M (SD)

End-product k = 15, n = 6 6.53 (8.37) 10.07 (16.01) 11.20 (15.21) 5.87 (5.41) 7.67 (11.93) 6.00 (4.77)

k = 12, n = 7 7.67 (9.05) 12.25 (17.32) 10.17 (14.49) 5.92 (5.79) 7.92 (13.34) 5.17 (6.28)

k = 8, n = 8 6.38 (3.89) 14.50 (20.54) 14.00 (16.54) 4.88 (3.56) 5.63 (5.88) 4.38 (3.78)

k = 5, n = 9 6.80 (3.11) 12.80 (18.13) 20.80 (17.99) 4.20 (1.48) 7.20 (7.19) 2.60 (2.61)

k = 3, n = 10 7.00 (2.65) 19.33 (22.28) 14.33 (18.93) 4.00 (2.00) 5.00 (3.61) 1.33 (0.58)

Action k = 18, n = 6 2.67 (4.24) 5.61 (7.29) 7.11 (12.42) 7.39 (6.02) 4.56 (4.61) 7.78 (8.72)

k = 12, n = 7 2.17 (3.13) 4.83 (6.66) 8.83 (14.65) 9.25 (6.41) 5.50 (5.25) 6.00 (6.48)

k = 10, n = 8 2.40 (3.37) 5.50 (7.12) 10.10 (15.84) 7.40 (4.79) 6.10 (5.55) 5.20 (6.41)

k = 5, n = 9 0.20 (0.48) 3.00 (2.65) 15.80 (21.58) 8.40 (6.23) 5.40 (3.91) 11.40 (12.30)

k = 4, n = 10 0.25 (0.50) 2.00 (1.63) 8.00 (14.67) 7.75 (6.99) 6.00 (4.24) 2.75 (1.71)

End-product and Action

k = 15, n = 6 2.73 (3.54) 8.93 (16.43) 4.40 (2.82) 9.67 (13.37) 7.87 (10.00) 10.33 (11.95)

k = 13, n = 7 2.92 (3.77) 10.23 (17.36) 4.62 (2.96) 11.08 (13.87) 8.62 (10.56) 12.00 (11.16)

k = 9, n = 8 3.56 (4.39) 10.89 (20.82) 4.56 (2.83) 8.56 (2.83) 5.67 (5.98) 6.89 (2.76)

31

k = 6, n = 9 4.50 (4.93) 14.17 (25.50) 4.67 (3.45) 8.50 (13.11) 3.50 (1.98) 5.50 (3.56)

k = 4, n = 10 2.75 (3.40) 20.00 (30.78) 4.75 (4.27) 2.75 (4.86) 3.25 (1.89) 2.00 (1.83)

Asocial k = 13, n = 6 5.92 (5.89) 2.23 (1.83) 4.23 (5.86) 5.92 (8.35) 4.69 (3.88) 4.15 (4.91)

k = 3, n = 7 8.00 (10.39) 2.00 (1.73) 6.00 (6.00) 13.67 (15.14) 4.33 (4.16) 2.00 (2.00)

k = 2, n = 8 11.00 (12.73) 1.50 (2.12) 9.00 (4.24) 17.00 (19.80) 5.00 (5.66) 10.00 (0.0)

k = 2, n = 9 11.00 (12.73) 1.50 (2.12) 9.00 (4.24) 17.00 (19.80 5.00 (5.66) 2.00 (0.0)

k = 2, n = 10 11.00 (12.73) 1.50 (2.12) 9.00 (4.24) 17.00 (19.80) 5.00 (5.66) 8.50 (9.19)

32

ESM 3: Examples of devices

Highly Successful Devices

(> 95th percentile)

Average Devices

(held 6 weights)

Unsuccessful Devices

(no weights held)

47 weights

32 weights

41 weights

27 weights

33

ESM 4: Cultural accumulation results for groups of size 3-10: Page’s L trend test

Group Size Condition Number of Chains L Critical L p

3 or more End-product k = 23 284 288 .119Action k = 22 270 275 .183End-product and Action k = 21 262 263 .061

Asocial k = 26 310 324 .3904 or more End-product k = 21 534 547 .248

Action k = 22 578 573 .019End-product and Action k = 20 532 522 .006

Asocial k = 21 532 547 .2985 or more End-product k = 18 822 846 .286

Action k = 20 947 937 .018End-product and Action k = 17 808 800 .019

Asocial k = 17 775 800 .3146 or more End-product k = 15 1106 1153 .454

Action k = 18 1395 1378 .015End-product and Action k = 15 1167 1153 .017

Asocial k = 13 962 1003 .4097 or more End-product k = 12 1330 1410 .362

Action k = 12 1407 1410 .056End-product and Action k = 13 1557 1525 .007

Asocial k = 3 337 370 .4808 or more End-product k = 8 1257 1371 .193

Action k = 10 1649 1703 .282End-product and Action k = 9 1563 1537 .014

Asocial k = 2 336 362 .2979 or more End-product k = 5 1011 1204 .984

Action k = 5 1228 1204 .015End-product and Action k = 6 1449 1436 .028

Asocial k = 2 442 500 .39510 or more End-product k = 3 767 987 .997

Action k = 4 1318 1301 .025End-product and Action k = 4 1247 1301 .251

Asocial k = 2 594 670 .389

34