卫生纸的faq里说过practiced spellcaster是按照对玩家有利来判定的，原话如下：
The bonus from Practiced Spellcaster applies whenever it
would be most beneficial to the caster. A 4th-level cleric/4thlevel
fighter with the Healing domain and Practiced Spellcaster
would cast Conjuration (Healing) spells as a 9th-level caster
(base caster level 4th, +4 from Practiced Spellcaster, +1 from
the Healing domain). A 4th-level cleric/4th-level rogue with
Practiced Spellcaster who activates a bead of karma (from a
strand of prayer beads) would cast her spells as a 12th-level
caster (base 4, +4 from Practiced Spellcaster, +4 from bead of
karma).
而natural bond的描述和practiced spellcaster非常接近：
NATURAL BOND
Your bond with your animal companion is exceptionally
strong.
Prerequisite: Animal companion.
Benefit: Add three to your effective druid level for
the purpose of determining the bonus Hit Dice, extra
tricks, special abilities, and other bonuses that your
animal companion receives (see page 36 of the Player’s
Handbook). This bonus can never make your effective
druid level exceed your character level.
PRACTICED SPELLCASTER
Choose a spellcasting class that you possess. Your spells cast
from that class are more powerful.
Prerequisite: Spellcraft 4 ranks.
Benefi t: Your caster level for the chosen spellcasting class
increases by 4. This benefi t can’t increase your caster level
to higher than your Hit Dice. ...
所以，一个ranger 6/bm 1修了natural bond，应该可以认为其动物伙伴有效等级是10？