Computerized spell-check can be a handy time-saver when writing papers, and many students swear by it. However amazing it may be, though, spell-check is still just a computer program, and as such should not be considered a substitute for proofreading with human eyes. As evidence, here are three common mistakes that spell-check won’t catch.

Proper Nouns
Spell-check uses a dictionary to compare the words you type to existing words. Proper nouns, like names of people or places, usually won’t be in the computer’s dictionary, and so the spell-check will flag them as misspelled. This means that when you proofread, you’ll have to ignore the wavy underline under those names. But this can also backfire – what if you happened to misspell that name? The computer will underline it same as before, but your brain is already prepared to ignore underlining on that name so you run the risk of not catching it yourself. This is one reason I advocate actually printing out a hard copy of your paper and proofreading it old-school, with a red pen – you won’t have any spell-check markings to distract you, and you’ll be more likely to catch that misspelled name.

Homophones
Homophones are words that sound alike but are spelled differently. Common culprits for this category include assent versus ascent, affect versus effect, and which versus witch. The key here is that all of these words are spelled correctly, and your spell-check doesn’t have any way of knowing which one of them you meant. Some programs have a grammar check tool as well, but these programs can’t really catch context-based errors. Take the first example above. Do you mean assent (a statement of agreement) or ascent (a climb up a mountain)? Both are nouns, so their usage in the sentence would be similar. Your grammar check tool has no idea whether you are writing a legal document or a mountaineer’s biography, so as far as the computer is concerned, either one could be correct.

Typos that Convert One Word to Another
I recently read a book that was obviously proofread by a computer rather than a human, and the way I knew that was the presence of many errors of this type. Remember, a computer spell-check is only looking for words that aren’t in its dictionary – so if a typo causes one word to become another, your spell-check won’t catch it. An example from this book was the misspelling of “rib” as “rig.” Rig is a word, so the computer didn’t catch it. For that, you need a pair of human eyes.

The overall theme with these mistakes is the computer’s inability to discern context. Spell-check is there to make sure that you’ve spelled your words correctly, but it has no idea what you’re really trying to say and cannot fix things that don’t involve misspelled words. This is one of the reasons that I advocate students not rely on their spell-check – in much the same way that I encourage math students not to rely on their calculators. The computer doesn’t know the context – you do. Print out your paper, grab a red pen, and read through for errors without the computer around. Asking a friend to proofread your paper is also a good strategy – someone who hasn’t been staring at the same paragraphs for days will be more likely to notice the mistakes that your brain has learned to gloss over.