Now that we know how to define profanity and why we should be careful of our words, let’s look at how the brain processes swear words. In our brains, the cerebral cortex, in the left hemisphere, processes our language (language meaning “the words we speak” not “swear words”.) Scientists recognize this as a ‘higher’ function. The brain processes emotions and instincts deep inside itself, and the right hemisphere takes care of the emotional parts of language. Scientists classify emotions and instinct as ‘lower’ brain functions. Researches have been conducted showing that the brain processes swearing in the emotion and instinct regions, and instead of processing the words as units of sound that must be combined, it stores swear words as whole units. The left hemisphere isn’t even involved. “Functional magnetic resonance imaging (fMRI) studies have shown that the higher and lower parts of the brain can struggle with each other when a person swears [ref]. A New York Times article  cites several other studies that involve how a healthy brain processes swearing. For example, the brains of people who pride themselves on being educated respond to slang and "illiterate" phrases the same way they do to swear words. In addition, in studies in which people must identify the color a word is written in (instead of the word itself), swear words distract the participants from color recognition. You can also remember swear words about four times better than other words [ref].” So using swear words comes directly from the emotion portion of the brain. The Bible classifies those who operate by instinct as godless men that deny the Lord Jesus and exploit his grace. “Yet these men speak abusively against whatever they do not understand; and what things they do understand by instinct, like unreasoning animals — these are the very things that destroy them (Jude 10, emphasis mine).”
So let’s sum up. Our English language contains words that we instinctively recognize as swear words. God’s Word contains standards for our speech, and the words we should and should not say. He wants us to avoid coarse and corrupt speech. Our brains process swear words in the emotion/instinct portion of the brain, not the language processing unit. Thus, if we give free rein to our instincts, we act as animals and godless men. I think many agree with me at this point that speaking swear words is wrong, so allow me to take you one more step. Reading them is not only unnecessary, but highly questionable.
“Above all else, guard your heart, for it is the wellspring of life” (Proverbs 4:23, emphasis mine). And lest we excuse the issue by saying that this refers to the heart, not the mind, the Hebrew meaning for the word ‘heart’ in this verse means “the heart; also used (figuratively) very widely for the feelings, the will and even the intellect; likewise for the centre of anything.” As the final clincher, see this verse: “For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false testimony, slander” (Matthew 15:20, emphasis mine). And the Greek for ‘heart’ in this verse means: “the heart, i.e. (figuratively) the thoughts or feelings (mind); also (by analogy) the middle.” The Bible tells us here to guard our intellect, our brain. Remember where swear words come from? The emotion or feeling section of the brain. So, if we read in books these words that we’re supposed to guard our minds from, then we are not properly guarding our intellect and emotions. Now, before you throw away anything, come with me just a little farther. I am not saying that you must never, ever read a book with a swear word in it. If you try to avoid all profanity, you will be subjecting yourself to a great many headaches and heartaches. We live in a fallen world, and if we try to throw out every book that has something wrong in it, then we’re going about the issue the wrong way. Aside from the Bible, all other books are written by finite, human authors. They cannot possibly produce a story that is free from error.