Theory:

     If there is a part of the brain especially devoted to mischief, that part was largely developed in Toto. He was always tearing things to pieces. Whenever one of my aunts came near him, he made every effort to get hold of her dress and tear a hole in it.
 
     One day, at lunch-time, a large dish of pullao stood in the centre of the dining-table. We entered the room to find Toto stuffing himself with rice. My grandmother screamed — and Toto threw a plate at her. One of my aunts rushed forward — and received a glass of water in the face. When Grandfather arrived, Toto picked up the dish of pullao and made his exit through a window. We found him in the branches of the jackfruit tree, the dish still in his arms. He remained there all afternoon, eating slowly through the rice, determined on finishing every grain. And then, in order to spite Grandmother, who had screamed at him, he threw the dish down from the tree, and chattered with delight when it broke into a hundred pieces.
Explanation:
 
The narrator exaggerates Toto's biological design or nature while describing Toto's mischievous deeds. He says, if there is anything like a portion of the brain dedicated explicitly to mischief, it was significantly developed in Toto.

Toto was constantly tearing things apart. When the narrator's aunt approached Toto, it grabbed her dress and tore a hole in it. One day at lunch, a large dish of pullao was set in the centre of the dining table. When the narrator's family entered the room, they were shocked to see Toto was stuffing itself with rice.
 
Toto on the dining table.jpg
Toto on the dining table
 
When the narrator's grandmother screamed at it, Toto threw a plate at her. One of the narrator's aunts ran up to Toto and was hit in the face with a glass of water. Toto picked up the pullao dish and left through a doorway while the narrator's Grandfather approached the dining room. Nobody could keep Toto under control.
 
It moved to the top of the jackfruit tree, keeping the pullao dish in its hands. It didn't come down the tree but stayed there all afternoon.
 
Monkey on a jackfruit tree.jpg
Monkey on a jackfruit tree
 
The narrator's family noticed Toto taking his time finishing the pullao. It might be that the pullao had been so tasty to Toto's tongue that it didn't waste a single grain and ate everything.
 
In the end, to punish the grandmother who had screamed at him, it threw the dish from the tree, giggling with delight as it dropped into a hundred pieces.
 
Toto’s revenge on grandmother.jpg
Toto’s revenge on grandmother
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Spite
Deliberately hurt, irritate or offend someone
2.
Stuff
To fill with something
3.
Scream/YellTo make a loud, high-pitched sound
4.
HurlTo throw something with great force
5.
Determined Having made a definite decision to do something
6.
ChatterTo make a series of quick high-pitched sound
7.
Explicitly In a clear or detailed manner
8.
ExaggerateTo enlarge something beyond truths
Reference:
National Council of Educational Research and Training (2006). Moments. The Adventures of Toto – Ruskin Bond (pp. 7-10). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.