Sensory Integration Education

Teresa A. May-Benson, Sc.D., OTR/L, FAOTA, is a world-renowned lecturer and researcher on sensory integration. She is the author of the Adult/Adolescent Sensory History (ASH), the Gravitational Insecurity (GI) Assessment and the Test of Ideational Praxis in addition to numerous articles and book chapters on praxis, ideation, and sensory integration. She has extensive experience with children and adults with autism and a diverse clinical background having worked in private and public school settings as well as private practice. She is past chairperson of the Sensory Integration Special Interest Section of the American Occupational Therapy Association. She is the recipient of the Virginia Scardinia Award of Excellence from AOTF, The Alice S. Bachman Award from Pediatric Therapy Network, and the Catherine Trombly Award from the Massachusetts Association of Occupational Therapy.

What is Gravitational Insecurity?

Gravitational insecurity (GI) is an emotional or fear reaction to movement experiences that is out of proportion to the actual danger or threat of the movement identified by A. Jean Ayres as early as 1972. It is typically observed in response to unexpected vestibular-proprioceptive stimuli or changes in the position of the body in space (especially where the feet leave the ground or are no longer in contact with the floor (Bundy & Lane, 2020). GI is considered to be a vestibular-based sensory integration problem and is identified and treated almost exclusively by sensory integration trained occupational therapists. It is a condition little known outside of occupational therapy.

Status of the Evidence for GI

While the clinical presentation of GI has been known since the 1970’s and this sensory integration-based problem is routinely identified and treated by occupational therapists, there is remarkably little empirical evidence on this problem. A scoping review (MayBenson & Teasdale, 2018) was completed which summarized the state of the existing literature on the construct of gravitational insecurity. Research studies, articles, book chapters and grey literature (e.g. theses, dissertations, posters, unpublished papers) published between 1972 and 2016, written in English, which specifically addressed or discussed gravitational insecurity were examined. Chapters or articles which just mentioned GI as one type of modulation or sensory processing problem were excluded.

A total of 23 documents were identified with three of those documents being follow up publications of other documents (e.g. theses). Information on both children and adults was reviewed. Results found that studies originated either in the US or in India and 18 of 23 documents were generated by 3 authors/ labs (i.e. Koomar, May-Benson or Ganapathy Sankar). Peer-reviewed articles primarily examined assessment of GI while grey literature such as book chapters, theses and posters described clinical characteristics of GI and intervention techniques which have become “standard practice” in sensory integration-based occupational therapy. However, as of this review there was little peer-reviewed empirical research to support the GI construct or its intervention. Since that time several studies have been completed which provide additional evidence for our understanding of GI. This article will review the current status of GI and present a summary of new empirical research supporting GI.

Status of the Construct of GI

Initial description of characteristics of GI (e.g. fear of playgrounds, falling, or sudden movements; dislike head back) were described by Ayres (1979) and these core characteristics have been cited since that time. The specific neurological underpinnings of GI, however, are currently unknown. (Ayres, 1972, 1979) hypothesized that GI was a vestibular deficit of modulation of gravity perception which contributed to a fear of movement. Fisher & Bundy (1989, 1991) later proposed that deficits of otolith functioning served as the underlying mechanism of GI. Only two studies have examined the physiological responses associated with GI. Weisberg (1982, 1984) contributed to the neurophysiological understanding of GI in her study of children with developmental delays. She found several children with a high resting state of arousal as measured by electrodermal responses (EDR) that demonstrated fearful responses to unexpected movement stimuli. She suggested that individuals with GI might have a sensory modulation problem associated with high physiological arousal.

Similarly, Koomar (1996) and Gerard (1991) found that GI was related to anxiety and dyspraxia in children and that children with GI demonstrated high cortisol and low heart rates suggesting high arousal states similar to that found by Weisberg. However, only one of these studies was peer-reviewed.

Status of Understanding of Characteristics of GI

Ayres initially identified a condition characterized by a fear of movement in 1972. She expanded on this construct in her book SI and the Child (Ayres, 1979) where she specified this condition as gravitational insecurity and articulated key characteristics of this disorder which are still used today. Behaviors characteristic of domain of gravitational insecurity including fear of feet off ground, being on high surfaces, backward or upside-down head movement, or disorienting visual stimuli were identified by Lee (1987). None of these studies were peer-reviewed.

Status of Assessment of GI

Development of assessments for GI has demonstrated the strongest research evidence with 8 peerreviewed journal articles and one thesis. May (1989) and May-Benson & Koomar (2007) developed the Gravitational Insecurity Assessment (GI Assessment) for school-aged children (5 – 10 years of age) demonstrating preliminary psychometrics and then examined GI in typical preschool children (2 – 4 years of age). They found that typical children perform the items on the test easily, with no hesitation and with no fear or postural challenges. An age trend was found in 2 – 4-year olds but not 5 – 10-year olds. Performance of typical school aged children 3 – 10 years of age in India was examined in a series of studies by Ganapathy Sankar and Ganapathy Sankar & Prema (2011 – 2015). They found an age trend in the development of gravitational security in these children.

Status of Intervention for GI

Literature on intervention for GI was found only in grey literature of four primary book chapters (Ayres, 1972, Fisher & Bundy, 1989, Koomar & Bundy, 2002). In her book, Sensory Integration and Learning Disabilities, Ayres (1972) first identified intervention strategies using slow, low amplitude linear movement as the preferred sensory inputs to treat GI. These techniques were expanded upon by Fisher & Bundy (1989) in a chapter on vestibular dysfunction. They provided a number of activities and recommended using activities that provided slow, linear movement with the client’s feet on ground.

These techniques were finally expanded on by Koomar & Bundy (1991, 2002) in the first two editions of Sensory Integration Theory and Practice. They provided extensive suggestions for treating GI and further supported the use of linear movement and proprioception as primary sensory activities to treat GI. Nearly every book chapter on sensory integration mentions GI as an SI problem and provides some information on intervention, all of which originated with these three references. No intervention studies have specifically examined intervention for GI and recommended intervention strategies are based only on theory.

Advances in Research on GI

Empirical research on GI has been very sparse and largely limited to assessment. In the last five years, however, a number of studies have been completed which have expanded our understanding of gravitational insecurity in several areas.

Advances in Descriptive Research on GI

Three recent studies have advanced our understanding of the characteristics of gravitational insecurity. Potegal, Pfaff, & Kroker (2018) conducted a survey study of occupational therapists working with children with GI. Responses of 109 OTs suggested that GI occurs in 0–5% of most pediatric OT populations. Children's willingness, fear and hesitancy when climbing was the most typically assessed behavioral characteristic of GI reported by OTs. In this sample, therapists reported GI to be more prevalent in girls than boys and in 3–6 year olds than in other pediatric age groups. GI was reported to be associated with vestibular dysfunction, Developmental Coordination Disorder and anxiety. GI was reported to be treated with gradual linear-to-rotational movement and/or the Astronaut Training Program. About a third of children were reported to show little or no change, a third improved somewhat, a third improved greatly. About 26% of these children showed post-treatment “craving” for previously avoided movements potentially suggesting decreased vestibular processing underlying the fear of movement. This survey study provided some understanding of the clinical presentation of GI as reported by clinical occupational therapists.

A recent article by May-Benson, Gentil & Teasdale (2020), however, examined symptoms of GI in a clinical population of 689 children with known sensory integration problems (SPD), using a parent report sensory history. They found prevalence of symptoms of gravitational insecurity in this clinical population of children with SPD to be 15 – 21%. This is significantly higher than that reported by Potegal, et al. (2018).

They also found that the number and patterns of gravitational insecurity symptoms were not significantly different across age, gender or comorbid diagnoses in a pediatric population. Frequent observation of the behavior of “hesitates going down stairs” most discriminated between children with GI characteristics and those without. Behaviors of “upset if head tilted backwards”, “dislikes elevators/escalators”, “not alternate feet down stairs” and “hesitates climbing” had similar discriminatory ability. Additional behaviors of “dislikes being tipped upside down”, “dislikes fast rides” and “fearful of catching balls” were also found to be important. These eight behaviors, when observed to be present frequently, accurately predicted GI for 93% of cases. This study suggested that GI, even at a mild level, is highly prevalent in children with sensory integration problems and that the eight stated behaviors are important in screening for this population.

The relationship of GI symptoms to other areas of sensory integration functioning was also examined using a sensory history which has contributed to our understanding of this construct in children. May-Benson, Gentil & Teasdale (2020) found GI was significantly related to motor skills performance (r=.395, p < .001) indicating the more severe the GI the more motor coordination challenges were present. Further, an expected negative relationship was found between GI and nonGI movement activities (r = -.221, p < .001) indicating that the more severe the GI, the less individuals engaged in other movement activities. Small relationships between GI and visual spatial skills (r=.259, p < .001), auditory processing (r=.221, p < .001), and tactile processing (r=.286, p<.001) were found supporting an overall relationship of gravitational insecurity symptoms to other sensory processing challenges.

May-Benson, Faria & Teasdale (2015) also examined GI in 1392 typically functioning adults using the Adult/Adolescent Sensory History (ASH), a self-report sensory questionnaire. Eight items on the ASH identified behaviors characteristic of GI. These included “dislikes elevators or escalators”, “seems fearful of heights”, “hesitates or avoids climbing ladders”, “avoids fast carnival rides that spin”, “avoids roller coasters”, “dislikes flying in airplanes”, “fearful of catching balls” and “has difficulty traveling through a tunnel without discomfort.” x. May-Benson, et al. found 19% of typically functioning adults reported symptoms of mild to definite GI suggesting that some fear of movement is present in the general adult population. They also found that, in adults, women have more severe GI than men. GI symptoms were also slightly more common in individuals over the age of 65 years. Consistent with findings in children, GI problems were found to be associated with motor planning (r=.33), anxiety (r=.31), movement processing (r=.63) and visual-spatial skills (r=.37) as well as having a negative impact on driving (r=.50). Thus, recent studies have supported and identified characteristics of GI in both children and adults. In addition, these studies have supported the relationship of GI to praxis, vestibular sensory processing and visual-perceptual skills.

Advances in Assessment of GI

Two studies have recently advanced assessment of GI by examining the use of two measures in the assessment of adults. The first study (Ruzzano & May-Benson, 2017) examined the relationship of the GI subscore of the ASH with the GI Assessment -Revised (an objective administered assessment developed for children) with 52 typically functioning adults and 12 otherwise typically functioning adults with suspected GI. A moderate negative correlation was found between the GI-AssessmentRevised total score and the ASH-GI score (r = -.39, p < .01). Spearman correlations found a strong moderate relationship between the Emotional/Avoidance Response subscore of the GI AssessmentRevised and the ASH-GI score (r = -.39, p < .01) and a small nonsignificant relationship with the Postural Response subscore of the GI Assessment-Revised (r = -.22, p > .05). This supported a relationship between self-report of behaviors characteristic of GI and direct assessment of the condition in adults.

(May-Benson, Ruzzano & Teasdale, 2020) further examined the performance of typical and fearful adults on the GI Assessment-Revised. An age and gender matched group of 12 typical and 12 fearful adults was examined. One-tailed paired t-tests of the matched group found the fearful group had significantly lower scores on the total score of the GI Assessment-Revised (t(11) =-2.27, p = .022) and the Emotional/ Avoidance Response subscore (t(11) = -2.93, p = .070). The Postural Responses subscore approached significance. Of the eight items on the GI Assessment-Revised, related-samples Wilcoxon Signed Rank tests found the fearful group had significantly lower scores on the Tiltboard Tip, Supine on BallActive, and Supine on Ball-Passive suggesting these items may be the most discriminatory items for use with adults. As previously reported with children, typical non-fearful adults had near perfect scores. 

As with children, this measure significantly discriminated even mild fear of movement in otherwise typical adults suggesting this measure is appropriate to use with adults as well as children.

Advances in Neurophysiological Understanding of GI

More recently Potegal (2015) and Potegal & May-Benson (218) proposed additional vestibular connections to GI and specifically suggested a specific neurological condition known as a leaky vestibular velocity storage as a potential primary cause of GI. This hypothesis was recently empirically examined in a group of 17 pairs of typically functioning adults matched by age and gender to adults with self-reported hesitancy and fear responses to balance and movement challenges characteristic of GI (Potegal, May-Benson, Oxborough, Hall & McKnight, 2020). Balance symptoms related to GI as well as balance confidence and fearfulness, sensory hypersensitivities, spatial orientation skills and anxiety were examined through self-report measures, posturography testing, and vestibular-ocular responses to rotation.

Posturography testing involved standing balance under visual and proprioceptive conditions and vestibulo-ocular nystagmus was examined under sinusoidal and unidirectional rotations. Results during posturography testing found that, when relying only on vestibular inputs, adults with GI symptoms responded to the movement challenge with excessive compensatory hip movements suggesting inefficient vestibular processing and postural responses.

Most interestingly, rotation testing found that adults with GI symptoms had vestibular-ocular responses to rotation that were characterized by less low frequency gain and modestly but significantly shortened velocity storage time constants. These findings supported the proposed deficits in vestibular velocity storage (VVS) in adults who demonstrate behaviors characteristic of GI. The VVS hypothesis opens the possibility that at least some symptoms of GI may be caused by deficits in this brainstem circuit that amplifies the weak vestibular signals generated by small/slow head movements.

In addition to differences between the typical and GI symptom groups, findings found significant correlations between a self-report measure of Gi symptoms and severity of postural and VVS responses as well as a measure of problematic spatial orientation. This study used basic neuroscience tests to support the presence of vestibular and postural challenges in individuals demonstrating behaviors characteristic of GI as well as supporting the relationship of GI to spatial orientation skills.

Implications for OT Practice

Among sensory integration disorders, gravitational insecurity is particularly important to identify and treat because of its relationship to fear responses and high anxiety. To date there is little peer-reviewed information on this condition to guide evidence-based practice. Grey literature is present in many forms. Recent research supports the characteristics of GI and has increased our understanding of the prevalence of this condition in both children and adults.

Literature supports the use of the standardized GI Assessment – Revised with both children and adults to identify GI. Use of specific items on some sensory histories for children and adults may also be helpful in identifying this problem. Most exciting, recent neurophysiological testing supports the presence of vestibular dysfunction as a foundation for GI. Empirical research is needed on intervention strategies for GI to provide evidence for best practice for clinicians. Lastly, the known relationship between GI and anxiety in both children and adults needs to be further examined.