Thank you, thank you.
rea·son ( P ) Pronunciation Key (rzn)
n.
The basis or motive for an action, decision, or conviction. See Usage Note at because. See Usage Note at why.
A declaration made to explain or justify action, decision, or conviction: inquired about her reason for leaving.
An underlying fact or cause that provides logical sense for a premise or occurrence: There is reason to believe that the accused did not commit this crime.
The capacity for logical, rational, and analytic thought; intelligence.
Good judgment; sound sense.
A normal mental state; sanity: He has lost his reason.
Logic. A premise, usually the minor premise, of an argument.
Basically, by saying that non-human animals have no capacity for reasoning, you're saying that a rat cannot tell the difference between a piece of fruit and a pebble.