SLPs often wonder what words are the most ideal treatment targets. A body of research (e.g., Morrisette & Gierut, 2002; Storkel & Morrisette, 2002) demonstrated that high-frequency words led to greater generalization than low-frequency words. As a result, this resource of high-frequency words (based on adult lexicon) was created to identify ideal targets.
Recently, the leading researchers in this area (the same ones who compared high-frequency and low-frequency) have investigated the impact of high-frequency real words vs. nonwords. So far, the results are suggesting that nonwords lead to better results. The two most recent studies (Gierut & Morrisette, 2010; Gierut, Morrisette & Ziemer, 2010) are accessible here and here. Like all research, more needs to be done to investigate these findings. For now, the authors recommend that if SLPs treat real words, they should be high-frequency. Nonwords are also viable targets.
The attached document also includes both high- and low-density words. The density of a word is the number of phonetic counterparts the word has if you add, delete or substitute a sound. For example, the word "feet" has ten counterparts in its neighborhood, including fleet, meet, fee, eat, foot, fate, fight, fit, fat and fete. "Feet" is considered a low density word because it has ten or fewer counterparts. Words with 11 or more counterparts are considered to be high density. Typically, these are words that sound like a lot of other words, such as word family members. The recommendations differ according to the child’s sound disorder typology. For students with phonological disorders, it is recommended that SLPs select five low-density words and five high- density words for the most ideal, balanced targets for a given sound. The researchers have posited that it is best to balance lists with both high and low density words because each kind facilitates a different aspect of generalization (untreated vs. treated sounds).
For students with articulation disorders (often one or two sounds), it is recommended that SLps treat low-density words because research suggests that low-density words promote greater generalization to the treated sounds. For example, if a child is only working on the /r/ sound, SLPs would target low-density /r/ words in a particular context, such as prevocalic.
There are several references at the end of the handout if you are interested in reading more about this line of thought.