Often, either a single variable or two or more variables will strengthen more than one response simultaneously. If either or both of the responses are complex, or composed of several elements, the possibility exists that the response form that actually is emitted will be composed of elements or fragments of each response. These recombinations of fragments are sometimes called slips of the tongue or are situations in which we say that we misspoke. The effects of fragmentary recombination can often be seen in the words that result from trying to say tongue twisters.