Some contemporary psychologists say that one should not use the behaviourist method with his children, meaning, he should not only avoid punishing or threatening them, but also not reward them with praise or the like, because this is conditioning the child and he will make his behaviour dependent on the external influence and not on internal cognition processes.
How do you evaluate this from a psychological and Islamic perspective?
In the Islamic context, the concept of Jahannam and Jannah are both examples of behaviorism. The Prophet (ﷺ) has mentioned that rewarding and punishing children is part of their upbringing, for example, correcting them when they do not pray. However, at the same time, we do not rely only on this method. It is true that solely using behaviorism will not give effective results.
We find many examples in the Sunnah where the Prophet (ﷺ), encouraged us to work on the hearts of people while giving da’wah. For example, when the Prophet (ﷺ), sent Muadh to Yemen, he said, "Invite the people to testify that none has the right to be worshipped but Allah and I am Allah's Apostle, and if they obey you to do so, then teach them that Allah has enjoined on them five prayers in every day and night, and if they obey you to do so, then teach them that Allah has made it obligatory for them to pay the Zakat from their property and it is to be taken from the wealthy among them and given to the poor." 
The first invitation was to accept Islam i.e. an internal change, before outward actions like Salah and Zakah.
When teaching children, it is important to help them understand the belief in Allah, angels, the Hereafter, and so on, and not just the outward actions like prayer and fasting. Priority is given to teaching children tawheed since this is the foundation of Islamic faith. Children should be taught the ways and means to connect to Allah. The love of the Prophet (ﷺ) and the Sahabah should be instilled so that the child would be proud to imitate them in belief, dress and manners. When the inner self is strengthened, the outside will follow.
We see the precious advice given by Luqman to his son:
وَإِذْ قَالَ لُقْمَانُ لِابْنِهِ وَهُوَ يَعِظُهُ يَا بُنَيَّ لَا تُشْرِكْ بِاللَّهِ ۖ إِنَّ الشِّرْكَ لَظُلْمٌ عَظِيمٌ
"O my son! Join not in worship others with Allah. Verily, joining others in worship with Allah is the greatest injustice/oppression indeed."
Thus, Islam encourages us to work on the inner self of humans, and then give reward or punishment for outwards actions. This is a comprehensive approach.
And Allah knows best.
 Sahih Al- Bukhari
 Surah Luqman, 31:13< Back to Questions