DIBELS First Sound Fluency (FSF)

Daze Administration Timeline

Description of the FSF Measure

DIBELS First Sound Fluency (FSF) is a standardized, individually administered assessment that provides a measure of phonemic awareness skills in the beginning and middle of kindergarten. FSF is available in DIBELS Next and replaces Initial Sound Fluency (ISF), an earlier measure of phonemic awareness. FSF measures how well a student can hear and produce the initial sounds in words. Each administration includes up to 30 stimulus words presented verbally by the examiner. The assessor scores each response with 2, 1, or 0 points: A correct, isolated initial sound receives 2 points, initial sounds or blends receive 1 point, and an incorrect sound receives no points. The assessor continues to present words for up to one minute, or until all 30 words have been presented. FSF is not prorated.

FSF directly measures one of the Big Ideas in Beginning Reading: Phonological Awareness. The construct of phonological awareness includes a range of skills of varying degrees of difficulty. FSF measures a subset of these skills, that tends to be easier for younger students because there are fewer demands on working memory (i.e., students are only asked to produce the initial sound in words). As with most measures of phonemic awareness, FSF appears to work best with young students and may not be as useful for students who are already very proficient at identifying initial sounds.

Differences between the 6th Edition ISF and Next Edition FSF

  • ISF requires visual stimulus materials (pictures) and FSF relies entirely words presented verbally by the examiner.
  • FSF does not require or allow for a selection response, while 75% of items on ISF permit selection responses. With FSF all responses include student production of the initial sounds.
  • ISF allows for a motor response (pointing), FSF does not.
  • FSF includes differential scoring (i.e., 2 points, 1 point or no points) depending on the type of student response. ISF allows 1 point for each response.

Summary of Technical Adequacy for FSF in Kindergarten


Type Reliability
Alternate form 0.82


Type: Measure Validity
Predictive: FSF beg/PSF mid 0.51
Predictive: FSF mid/PSF end 0.46
Predictive: FSF mid/NWF end 0.41
Concurrent median 0.51

Cummings, K. D., Kaminski, R. A., Good, R. H., & O'Neil, M. (2011). Assessing phonemic awareness in early kindergarten: Development and initial validation of first sound fluency (FSF). Assessment for Effective Intervention, 36(2), 94-106.

How does FSF link to the Big Ideas in Beginning Reading?

FSF is a measure that assesses phonemic awareness skills.

To learn more, visit the Big Ideas in Beginning Reading website.