The Minimal Pairs Test – A Tool to Assess Speech Discrimination & Optimize Cochlear Implant MAPs

Speech discrimination is a skill necessary to build speech comprehension. Minimal pairs can be a useful tool to evaluate an individual’s ability to discriminate between two words that only differ in one speech sound.

What Is a Minimal Pair & How Can They Help Assess Speech Discrimination?

Minimal pairs offer a practical and convenient way to evaluate an individual’s ability to discriminate between two phonemes (i.e., speech sounds). These phonemes, or segmental speech sounds, can be either a consonant or a vowel.

Essentially, a minimal pair consists of two words that differ by a single speech sound (i.e., phoneme). For example, hat (i.e., /hæt/) and cat (i.e., /kæt/) have contrasting initial sounds, but the rest of the sounds are identical, so they represent a minimal pair.

Minimal pairs are a useful way to assess the higher-level, segmental auditory discrimination skills of children and/or adults who rely on cochlear implants to listen to and understand spoken language. Thus, when a child or adult fails to recognize the difference between a minimal pair of words, they are likely to have a problem perceiving those specific sounds that differentiate the words from each other.

Before we begin, see if you can identify which of the following rows contain minimal pairs. Answers can be found at the end of the article.

Speech Discrimination vs. Speech Identification: The Hierarchy of Auditory Skills

First, it’s important to note that speech discrimination is different from identification. Discrimination means, “I know it is X, and not something else,” whereas identification says, “I know this is X and this is Y.”

Imagine hearing someone’s heavy footsteps in the hall and recognizing when you hear those same footsteps versus someone else’s footsteps. That’s discrimination.

Recognizing who every set of footsteps belongs to would be identification.

Speech discrimination and identification are higher level skills (Figure 1) and play an important role in overall speech perception skills.

The Role of Speech Perception in Children With Cochlear Implants

Phoneme perception of single speech sounds develops within the first year of life. In fact, infants can discriminate non-native vs. native speech sounds between the ages of 6 to 8 months. However, by 10 to 12 months, this ability diminishes as they consolidate their phoneme discrimination skills for their mother tongue.Werker, J. F. & Hensch, T. K. (2015). Critical Periods in Speech Perception: New Directions. Annual Review of Psychology, 66(1), 1–24. https://doi.org/10.1146/annurev-psych-010814-015104[1]

On the whole, the relationship between speech sound discrimination and spoken language development is complex. First, phonetic perception appears to play a vital role in early language development:

• Tsao, Lieu, and Kuhl (2004) determined that for typically developing children, the early speech perception skills in 6-month-olds predicted their word and phrase comprehension at the age of 2 years old. Among pediatric cochlear implant recipients, early speech perception skills also appear vital, not only to early language development but also to long-term skills.
  Tsao, F., Liu, H. & Kuhl, P. K. Speech Perception in Infancy Predicts Language Development in the Second Year of Life: A Longitudinal Study. Child Dev. 75, 1067–1084 (2004). https://pubmed.ncbi.nlm.nih.gov/15260865/
  [2]
• Hunter et al. (2017) found that early speech perception skills at 6 and 18 months post-implantation were associated with higher open-set word recognition at three to four years after surgery. Open-set word recognition was also then correlated with stronger language skills in adolescence to adulthood.Hunter, C. R., Kronenberger, W. G., Castellanos, I. & Pisoni, D. B. (2017). Early Postimplant Speech Perception and Language Skills Predict Long-Term Language and Neurocognitive Outcomes Following Pediatric Cochlear Implantation. Journal of Speech, Language, and Hearing Research, 60(8), 2321–2336. https://doi.org/10.1044/2017_jslhr-h-16-0152[3]

Children with cochlear implants are no exception to this. One of the more robust factors appears to be exposure to spoken communication in the environment, which consistently predicts higher speech perception performance.Geers, A. E., Mitchell, C. M., Warner-Czyz, A., Wang, N.-Y., Eisenberg, L. S. & Team, Cd. I. (2017). Early Sign Language Exposure and Cochlear Implantation Benefits. Pediatrics, 140(1), e20163489. https://doi.org/10.1542/peds.2016-3489[4]O’Donoghue, G. M., Nikolopoulos, T. P. & Archbold, S. M. (2000). Determinants of speech perception in children after cochlear implantation. The Lancet, 356(9228), 466–468. https://doi.org/10.1016/s0140-6736(00)02555-1[5]

For more on why early implantation is important, take a look at our article, Factors Affecting Communication Outcomes in Pediatric Cochlear Implantation.

Introducing: The Minimal Pairs Test

The Minimal Pairs Test is a closed-set test of more than 30 minimal pairs that assesses consonant and vowel contrasts. These test stimuli are divided in two separate lists of 15 pairs each (Sets A & B). Each list is balanced so that the same acoustic contrasts are evaluated. Examiners can then alternate test lists to reduce the potential of a practice effect over time.

The Minimal Pairs Test also includes a third list (Set C) that features six word pairs with reduced lexical difficulty for individuals with minimal vocabulary. Moreover, examiners have the option to customize their own list according to a child’s specific vocabulary needs by selecting specific stimulus pairs and using the blank record form (Form D) to record performance.

Examiners are encouraged to pre-teach test vocabulary, when necessary, as long as they avoid teaching the pairs together. Teaching pairs together requires auditory discrimination which is effectively the purpose of the test.

The Minimal Pairs Test is suitable for individuals 3 years of age or older. The test may be administered by speech and hearing professionals (e.g., speech-language pathologist, audiologist, hearing implant specialist, teacher of the deaf, etc.)

What’s Unique About the Minimal Pairs Test?

The Minimal Pairs Test takes auditory discrimination beyond the traditional boundaries of phoneme discrimination. Each minimal pair contrasts not only two phonemes but also presents a contrast of acoustic information.

For example, take the minimal pair hand-sand. The phonemic contrast assessed is /h/ vs. /s/. The sound /h/ has acoustic information (a formant) of approximately 1500-2000 Hz, whereas the formant for /s/ occurs at 5000-6000 Hz. When an incorrect selection is made—meaning the examinee selects hand instead of sand—it implies that they likely did not perceive the higher frequency acoustic information that allows differentiation between these two sounds.

The Minimal Pairs Test has also simplified the acoustic analysis of the speech discrimination errors. Examiners can record the listener’s response on the Record Form. On the form, each stimulus word is associated with a specific frequency range, and for MED-EL implant recipients, the corresponding electrode channels are also noted (Figure 2).

It’s important to note that these channel assignments only apply if all electrodes are active and no frequency band shift has been performed. When errors cluster within one frequency range, it can alert the clinician to the potential areas of concern to address when programming the device.

Cochlear Implant Recipients Can Benefit From Greater Collaboration

The Minimal Pairs Test is a more in-depth assessment of advanced speech discrimination skills that includes a streamlined process of acoustic analysis and interpretation for professionals. It encourages clinicians to monitor these skills over time with multiple word lists that present acoustically balanced stimuli. Altogether, this tool offers the opportunity for greater collaboration between speech-language pathologists, teachers of the deaf, and audiologists for the benefit of implant recipients.

More Resources on Speech Discrimination & Fostering Collaboration

For more resources related to speech sounds, check out our article Introducing: The Building Blocks of Speech. It provides additional free information about speech acoustics and speech development.

For additional ways to encourage collaboration between professionals who assist patients with hearing devices, please log in to your free MED-EL Academy account and then follow the link to our course How to Foster Beneficial Collaboration Between Audiology and Rehabilitation.