Co-Author: Ianessa A. Humbert, Ph.D., CCC- SLP

I am a current doctoral student pursuing my PhD in Rehabilitation Science at the University of Florida. I am studying under the mentorship and guidance of Dr. Ianessa Humbert. 

I first met Dr. Humbert late in my undergraduate career after hearing her present at a NSSLHA meeting. Admittedly, at the time, I hadn’t even realized that swallowing was something that people studied! However, I was intrigued by the science and desired to learn more. 

When I eventually began working with the Research Laboratory called the Swallowing Systems Core as an undergraduate volunteer, I did so lacking any sort of sufficient background in swallowing related science. Needless to say, the learning curve has been steep. 

What I’ve come to find, however, is that the learning never stops – or at least it shouldn’t. Learning is a humbling experience, but also a rewarding one.

The Power of Perspective

The perspective through which we look at something determines what we see. What we see, determines what we think. What we think, determines how we act.

In this way, perspective is powerful.

Therefore, it’s important to evaluate the perspective through which we see the world around us. When our perspective is narrowed, our ability to see the whole picture is limited. This can skew the way we think about what we see and ultimately affect the way we act.

A strong foundation in normal swallowing physiology is critical in order to differentiate normal swallowing differences from swallowing disorders.

Taking this into consideration, do we, as swallowing clinicians, need to evaluate our perspective when defining normal swallowing in day-to-day activities?

Difference vs. Disorder

Everyone’s “normal” is different. This is true in both life and in the treatment of swallowing.

Normative ranges for various swallowing durations and characteristics vary vastly (see Table 1 below). Because the spectrum of these normative values is so wide, a “normal” swallow for one individual may appear substantially different from the “normal” swallow of another individual.

Recognizing the potential for normal swallows to appear distinct from one another based on factors such as age, sex, and bolus size is key in order to differentiate between swallowing differences and swallowing disorders. 

In the field of speech and language pathology as a whole, it is well understood how difference vs. disorder applies to language development (i.e. an individual may speak with a different language or accent, but it does not mean that their language is disordered). However, within the realm of swallowing, this concept is often misunderstood. Swallowing differences are often mistaken for swallowing disorders, leading to a high amount of false positives diagnosed within the field.

Table 1. Normative Ranges for Swallowing Durations and Characteristics

The Prevalence of False Positives

A 2017 study by Vose et al., highlighted the frequency of false positive diagnoses in swallowing impairment identification. In this study, clinicians were asked to watch a series of three videoflouroscopy swallowing clips rated by complexity (i.e. easy, moderate, complex).

As clinicians, changing the perspective through which we see our patients may go a long way towards gaining a greater appreciation and understanding of the diversity in normal swallowing.

Upon viewing each clip, clinicians were asked to identify any problems they noticed within the swallow. Vose et al., found that 77% of clinicians diagnosed false positive impairments for the easy clip, 82% for the moderate clip, and 92% for the complex clip. In other words, normal physiology was frequently misdiagnosed as abnormal.

The possibility that a high prevalence of false positives is being diagnosed within the swallowing field may be attributed to a couple of factors, one of which includes insufficient swallowing training.

A 2008 article by Campbell and Taylor contended that many SLPs are inadequately trained in swallowing physiology. Currently, coursework on dysphagia is not mandated for graduate school programs, and for programs that do include coursework on dysphagia, oftentimes material is centered around abnormal swallowing.

Understanding disordered swallowing is important, yes, but perhaps more important is the ability to understand normal swallowing physiology. A strong foundation in normal swallowing physiology is critical in order to differentiate normal swallowing differences from swallowing disorders.

Inadequate exposure to the wide continuum and diversity of normal swallowing may create a narrow perspective through which a normal swallow is defined.  And again, perspective is powerful.

When possessing a narrow perspective of what defines a normal swallow, we are more prone to see “differences”, think these “differences” must be indicative of a disorder, and act quickly to treat the misdiagnosed disordered swallow.


Erring on the side of caution may occur with the best of intentions – perhaps clinicians are prone to over-diagnose because they “don’t want to miss anything.” However, the implications of these false-positive diagnoses arise a series of concerns both ethically and physiologically.

Ethically, billing patients for a disorder that they do not possess is wrong. Not only does treatment cost patients money, but it also costs time.

Physiologically, dietary modifications restricting the type and texture of food a patient can consume may decrease a patient’s desire to eat, limit their intake of nutrients, and potentially cause malnutrition. Furthermore, such modifications may negatively impact quality of life and inhibit an individual from comfortably participating in social interactions (i.e. eating out with friends/family).

So what now?

In order to be the change we want to see, perhaps we need to first change our perspective.

As clinicians, changing the perspective through which we see our patients may go a long way towards gaining a greater appreciation and understanding of the diversity in normal swallowing.

To do so, regardless of whatever stage one may be in in their clinical or academic career, humility will be required to challenge and change the status quo.

Humility requires self-reflection – the ability to look internally and honestly assess our own limitations. Awareness of own limitations is a key component of being clinically competent.

Dr. Harvey Max Chochinov writes:

“This awareness [of our own limitations] enables physicians to recognize and respect the expertise of others — a cornerstone of gratifying collegial relationships and well-functioning multidisciplinary teams. The nature of knowledge is impossible to contemplate or grasp in its entirety. In the face of new discoveries and insights, today’s medical wisdom may be destined to become yesterday’s folly…Physicians must be prepared to challenge fundamental assumptions and examine their practice patterns; they must consider credible evidence and be open to change. Humility dictates that no matter how great the measure of our reach, we acknowledge the limitations of our grasp.” 

It is important to note that acknowledging our knowledge gaps (i.e. humility) is not the same as embracing our knowledge gaps (i.e. complacency).

Humility serves as a driving force that propels us to seek knowledge through the recognition of our own knowledge gaps. Thereby, humility necessitates a willingness to learn.

Seeking out answers to unknown questions and incorporating evidence-based techniques into treatment ought to be an integral part of any clinician’s practice. Remaining up to date on current best-practice techniques not only benefits you as a clinician, but it also benefits your patients.

Practical Considerations

If you’re ready to bridge the knowledge gap, but are wondering how to begin, I’d suggest reviewing the following resources that address frequently misperceived swallowing events. All of the resources included below have been around for a number of years, none of the information published is “new” material.

Events that are commonly thought to be abnormal, but are not:

Delayed swallow onset

  • Note: Swallow initiation of normal, healthy individuals may occur when the bolus is past the valleculae
  • Source: Martin-Harris et al., 2007
  • PMID: 17538102


  • Note: Normal, healthy individuals penetrate and may sometimes achieve Penetration-Aspiration Scale scores of 2 and 3
  • Source: Rosenbek et al., 1996
  • PMID:  8721066

Event that is commonly overlooked, because normal physiology is often misunderstood:

Laryngeal vestibule closure

  • Note: Oftentimes clinicians focus on hyolaryngeal elevation, but neglect to focus on laryngeal vestibule closure
  • Source: Logemann et al., 1992
  • PMID: 1539666


Anderson, C., Macrae, P., Taylor-Kamara, I., Serel, S., Vose, A., & Humbert, I. A. (2015). The perturbation paradigm modulates error-based learning in a highly automated task: outcomes in swallowing kinematics. J Appl Physiol (1985), 119(4), 334-341.

Martin-Harris, B., Brodsky, M. B., Michel, Y., Lee, F.-S., & Walters, B. (2007). Delayed Initiation of the Pharyngeal Swallow: Normal Variability in Adult Swallows. Journal of Speech, Language, and Hearing Research, 50(3), 585–594. Retrieved from

Campbell-Taylor, I. (2008). Oropharyngeal dysphagia in long-term care: misperceptions of treatment efficacy. J Am Med Dir Assoc, 9(7), 523-531. doi: 10.1016/j.jamda.2008.06.001

Chochinov, H. M. (2010). Humility and the practice of medicine: tasting humble pie. CMAJ : Canadian Medical Association Journal, 182(11), 1217–1218.

Guedes, R., Azola, A., Macrae, P., Sunday, K., Mejia, V., Vose, A., & Humbert, I. A. (2017). Examination of swallowing maneuver training and transfer of practiced behaviors to laryngeal vestibule kinematics in functional swallowing of healthy adults. Physiology & Behavior, 174, 155-161. doi:10.1016/j.physbeh.2017.03.018

Humbert, I. A., Lokhande, A., Christopherson, H., German, R., & Stone, A. (2012). Adaptation of swallowing hyo-laryngeal kinematics is distinct in oral vs. pharyngeal sensory processing. J Appl Physiol (1985), 112(10), 1698-1705.

Logemann, J. A., Kahrilas, P. J., Cheng, J., Pauloski, B. R., Gibbons, P. J., Rademaker, A. W., & Lin, S. (1992). Closure mechanisms of laryngeal vestibule during swallow. American Journal of Physiology – Gastrointestinal and Liver Physiology, 262(2), G338 LP-G344. Retrieved from

Molfenter, S. M., & Steele, C. M. (2011). Physiological Variability in the Deglutition Literature: Hyoid and Laryngeal Kinematics. Dysphagia26(1), 67–74.

Molfenter, S. M., & Steele, C. M. (2012). Temporal variability in the deglutition literature. Dysphagia, 27(2), 162-177.

Robbins, J., Coyle, J., Rosenbek, J., Roecker, E., & Wood, J. (1999). Differentiation of normal and abnormal airway protection during swallowing using the penetration– aspiration scale. Dysphagia, 14(4), 228-232. doi:10.1007/pl00009610

Rosenbek, J. C., Robbins, J. A., Roecker, E. B., Coyle, J. L., & Wood, J. L. (1996). A penetration-aspiration scale. Dysphagia, 11(2), 93–98.

Vose, A., Kesneck, S., Sunday, K., Plowman, E.K., Humbert, I.A. (2017). A survey of clinician decision making when identifying swallowing impairments and determining treatment. (in review).