Table 5.

Contributions of each moderating variable to account for variance in effect sizes in bird studies

Moderator	F	Df1, Df2	p
Training and testing
Log training length	7.609	(1, 35)	.009**
Stimulus modality	6.407	(1, 35)	.016*
Test response	6.407	(1, 35)	.016*
Surface‐level properties
Categories in language	0.053	(1, 35)	.819
Number of unique vocabulary items	6.712	(1, 35)	.014*
Structural properties
Repetition of items	45.926	(1, 35)	<.0001***
Adjacent dependencies	2.462	(1, 35)	.126
Non‐adjacent dependencies	1.661	(1, 35)	.206

***p < .001, **p < .01, *p < .05.