My own guess is that both psychological and biological factors play a role.

These differences are largely related to biological and environmental factors.

However, there are biological factors that may affect the results of these tests.

Biological factors of an individual can affect their own L2 acquisition.

Several biological factors make women more vulnerable to the effects of alcohol than men.

It said chemical, biological and behavioral factors played an important role.

They have a meaning of their own and cannot be reduced to psychological or biological factors.

Overall, an interplay of biological, social and environmental factors can be considered.

This finding suggested a biological factor, which was then investigated further in the third study.

Biological factors can also be part of the cause.