physical rewards will encourage them as well, if not even more than something not physically tangible.
I agree that you could supplement the love but I think it is very wrong to say the physical rewards encourage more. Kids who get prizes from teachers who are not warm do not internalize the success the same as they do from teachers who give affection and pride.
A cool illustration of this – I ran a pre-school group and asked the teachers not to use “rewards” lichatchila. The children recieved praise and privileges and were very motivated. Sometimes I would give out treats and say, “the whole class is receiving this treat because of these 5 boys who had exceptional behavior this week (or day, or morning)”. Even though everyone got a treat, the other kids also wanted to be the ‘reason’ for the treat.