[The cleaning woman] thought that [Gregor] was deliberately lying motionless, pretending that his feelings were hurt; she credited him with unlimited intelligence. (3.30)
As you have probably noticed by now, Kafka's story is quite ironic about man's vaunted capacity for reason. It stages scene after scene where characters are unaware of the absurdity of their claims – not just Gregor, but the other characters as well. The irony is underscored here by the fact that the cleaning woman of all people is willing to ascribe to Gregor "unlimited intelligence." As far as we know, the cleaning woman's only area of expertise is, well, trash, refuse, garbage. Is the story suggesting that intelligence is, well, a waste?