Here is one quote from a discussion on spice non-linearity that explains it fairly well.
"Username | I have done this for a living for a very long time, and it never ceases to amaze me that some spices seem to grow exponentially. Especially the hot ones. So say you are making Vindaloo and it calls for 4 TB. seasoning, if you make a 4x batch, you should only double the spice, especially if you make it a day ahead. OR freeze it - seems to keep getting hotter. Other spices (besides seasonings heavy on hot peppers) that are brutal and potentially dish ruining if multiplied straight out are Cardamom and Cloves, Any of the Anises, dried herbs like thyme -but not rosemary, interestingly, Saffron, hmmm - some Paprikas, Coriander, Allspice, and oh God, Nutmeg. For a start, I would only double the spice for a 4x batch and taste it the next day. See what you think. The only spices I multiply straight out are Vanilla, Garlic, Black Pepper, and Cumin."
and another,
"Username | September 30, 2014 at 7:45 PM | Reply
Hi dear, I am gonna try this delicious dish on this Eid. If I make it with 4 chickens what proportion of spices and paste should I use? I am always confused with it.. Please can you suggest me?
Author | October 1, 2014 at 7:12 AM | Reply