Differed, deferred, offered, occurred: words like this featured in my 9-year-old daughter’s Spelling List last weekend, along with swimmer, travelled and others that either repeat the last letter of a verb when used in other forms, or they don’t. It got me thinking about rules of spelling and how we generalize information as we learn.

Why are “Mummy” and “Daddy” not spelt as “Mumy and Dady”? My daughter knew this one already. If they were spelt differently the pronunciation would be “Moo-mee” and “Day-dee”. We double up on consonants to make sure that words are pronounced correctly. You probably know this already and if so you probably worked it out for yourself. We learn how to spell things, actively or passively, and from lists when we’re at primary school, but generally we have to work out reasons and rules for ourselves. We find patterns and we generalize based on what we find.

Why does deferred have two “R”s and differed only have one? I asked my daughter this question to see if she could work out an answer, not expecting that she had been taught one. She couldn’t think of one, and there are probably many adults who couldn’t come up with a reason either. I don’t remember being taught a spelling rule about this but there must be one.

I figure it’s to do with stressed syllables and pairs of letters. “Differ” places the emphasis on the first syllable, and contains a double “F”. “Defer” places the emphasis on the second syllable, and only contains one “F”. “Travel” and “revel” would follow the same rule as “defer”, forming words like “traveller”, “travelled” and “revelled”. “Reveal” (with only one “V”) forms words with only one “L”, like “revealed” and “revealing”, so maybe the key rule is that the emphasis is on the second syllable rather than the first.

Generalizing information is a crucial part of learning. By the age of 5, if you have grown up in a house, you will know how a door works. No matter how big it is, or what colour it is, or whether it’s made of wood or glass, you will know how it’s supposed to work. Sometimes you turn the handle and push, sometimes you turn the handle and pull. By the age of 5 you will have done this often enough to open most doors.

If you have encountered and learnt enough past tenses that end in “-rred” (occurred, recurred, deferred) and enough that end in “-red” (differed, offered, suffered) you will be able to work out the correct form for any verb that wasn’t on any school-age spelling list, like proffer, buffer, prefer or infer. For the record it’s proffered, buffered, preferred and inferred, but you knew that already, and if my 9-year-old daughter doesn’t know it yet she probably will, soon enough.