TABLE 1.

Comparison of chinchilla and human head growth

% of Adult head size	Human head width (mm)	Human age (months)	Chinchilla head width (mm)	Chinchilla age (days)
70%	98.5 ± 1.96	~1	24.41 ± 1.90	~7
75%	107.8 ± 2.29	~3	26.15 ± 2.18	~14
80%	114.4 ± 3.9	~4	27.9 ± 1.89	~24
85%	121.13 ± 2.87	~7	29.64 ± 2.18	~28
90%	128.25 ± 3.04	~12	31.38 ± 2.12	~35
95%	135.36 ± 4.17	~30	33.13 ± 3.46	~42

The percentage of adult head size and the approximate time this occurs for both human and chinchilla is shown. The acoustical cues to sound location have been shown here, and in previous work, to be correlated with developmental increases in head diameter. Human data was generated from Davenport (1940).