Final answer:
Jerry forgets his loneliness from being isolated from his mother by playing with a toy, a doll.
Step-by-step explanation:
Jerry forgets his loneliness from being isolated from his mother by playing with a toy, a doll. This can be seen in the quote 'After failing to pass his doctoral examinations, Giorgio spends days in bed cuddling his favorite childhood toy.'
He finds a group of native boys to swim with. At first, they welcome him, but then they realize he is a foreigner and not a talented swimmer, and so, they leave him behind.
Hence, Jerry forgets his loneliness from being isolated from his mother by playing with a toy, a doll.