. Author manuscript; available in PMC: 2015 Mar 1.

Published in final edited form as: Anim Cogn. 2013 Jun 18;17(2):197–205. doi: 10.1007/s10071-013-0652-9

Table 2.

Yerkes chimpanzees

a. Choice part
	Inter-item interval for accumulation
	3s (Phase 1)		10s (Phase 2)		20s (Phase 3)

	% choice of 12 items	binomial test (n = 30)	% choice of 12 items	binomial test (n = 30)	% choice of 12 items	binomial test (n = 30)

Artemus	73	p = .016	80	p = .001	63	p = .200
Brandy	60	p = .362	63	p = .200	57	p = .585
Brodie^s	67	p = .099	53	p = .856	53	p = .856
Callie	57	p = .585	67	p = .099	57	p = .585
Cissie	93	p < .001	77	p = .005	93	p < .001
David^s	53	p = .856	53	p = .856	63	p = .200
Edwina^s	60	p = .362	60	p = .362	53	p = .856
Faye^s	60	p = .362	57	p = .585	50	p = 1.000
Foxy	70	p = .043	47	p = .856	77	p = .005
Frannie	53	p = .856	60	p = .362	57	p = .585
Julie	60	p = .362	73	p = .016	70	p = .043
Katrina^s	73	p = .016	53	p = .856	63	p = .200
Melissa	63	p = .200	67	p = .099	47	p = .856
Socrates^s	73	p = .016	67	p = .099	50	p = 1.000
Sylvia	60	p = .362	63	p = .200	57	p = .585

b. Accumulation part
	Inter-item interval for accumulation
	3s (Phase 1)		10s (Phase 2)		20s (Phase 3)

	mean items	one-sample t test	mean items	one-sample t test	mean items	one-sample t test

Artemus	11.55	t(21) = 16.60^***	10.57	t(23) = 17.41^***	5.42	t(18) = 1.74^ns
Brandy	11.72	t(17) = 27.80^***	9.05	t(18) = 17.28^***	2.88	t(16) = −2.38^od
Brodie	11.10	t(19) = 11.46^***	11.56	t(15) = 37.17^***	5.81	t(15) = 1.43^ns
Callie	12.00	N/A	12.00	N/A	10.06	t(16) = 5.78^***
Cissie	11.46	t(27) = 23.70^***	8.78	t(22) = 5.48^***	6.00	t(27) = 2.90^**
David	11.50	t(15) = 15.0^***	9.51	t(15) = 16.01^***	8.63	t(18) = 5.29^***
Edwina	11.11	t(17) = 11.66^***	9.83	t(17) = 5.87^***	6.94	t(15) = 2.30^*
Faye	11.72	t(17) = 27.80^***	12.00	N/A	11.40	t(14) = 18.50^***
Foxy	5.24	t(20) = 1.14^ns	2.14	t(13) = −7.32^od	2.35	t(22) = −4.91^od
Frannie	9.07	t(14) = 4.26^**	2.50	t(17) = −2.28^od	1.00	N/A
Julie	12.00	N/A	11.95	t(21) = 175.0^***	11.10	t(20) = 11.73^***
Katrina	11.95	t(21) = 175.0^***	11.88	t(15) = 92.22^***	11.95	t(18) = 151^***
Melissa	12.00	N/A	10.05	t(19) = 8.67^***	7.60	t(14) = 3.96^**
Socrates	11.00	t(21) = 10.14^***	6.95	t(19) = 3.69^**	2.80	t(14) = −2.17^od
Sylvia	9.28	t(17) = 8.44^***	2.89	t(18) = −5.50^od	1.94	t(16) = −6.80^od

Note:

exhibited a side bias in > 70% of trials;

^***

p < .001;

^**

p < .01;

p < .05;

^ns

not significant;

^od

significant in the opposite direction; N/A = not applicable (a t-test could not be conducted due to zero variance); italicized = failed to choose 12 items over 4 items in a post-hoc quantity judgment test