Study of Independent Walking in 17-month-old Twins

Updated: Aug 31, 2020

Independent walking (walking at will and without assistance) is fundamental to learning. The onset of independent walking triggers immediate, significant acceleration in language growth; a pattern that is stable and is evidenced across cultures (He, Walle, & Campos, 2015; Oudgenoeg‐Paz et al., 2012). Toddlers’ walking experience significantly predicts both receptive and expressive language growth with walking toddlers having significantly larger vocabularies than their age‐matched peers who are not yet walking (Walle & Campos, 2014; Walle & Warlaumont, 2015). Researchers have hypothesized that the connection of independent walking to increased language is a result of the new experiences that bolster toddlers’ language development (He et al., 2015; Walle & Campos, 2014; Walle & Warlaumont, 2015).

Independent walking requires an ever-improving coordination of sensory input with motor output. Overtime, sighted toddlers become increasingly more stable, able to deftly avoid collisions as they seek out objects and others.

When toddlers who are blind attempt to transition from adult assisted walking to independent walking they are challenged by their inability to visually avoid collisions.

three panels, first sighted twin reaching towards brother who is smiling, wearing his belt cane, both hands on cane, his father holds him from behind, Grace sqats next, tapping on a tank in front. pane 2, sighted twin pushes head of his brother, pane three, sighted twin moving away from crying brother.
Figure 1. Twin brothers interacting at the lab

Children with severely impaired sensory input exhibit delays in independent walking even when they possess the physical potential to walk. Delays in independent walking in learners who are visually impaired and blind (VI/B) are well documented. Researchers have found that learners aged five years and younger who are VI/B are less likely to achieve gross motor milestones on time (Bakke, Cavalcante, Oliveira, Sarinho, & Cattuzzo, 2019). Wyver and Livesey concluded that “findings are generally consistent despite the studies being conducted in a wide range of settings, in a variety of countries … there is strong evidence of an adverse impact of visual disability on motor development” (2003, p. 25).

The Pediatric Belt Cane (PBC) was developed to aid children with mobility visual impairment and blindness (MVI/B) independent walking by providing them with essential sensory input. MVI/B is defined as unable to visually avoid collisions with obstacles. The PBC is a custom-made wearable white cane invented in 2017 by collaboration of City University of New York medical device engineering and orientation and mobility professors. It provides tactile, haptic, and auditory feedback about the path ahead. Already, the PBC is being worn by almost 1000 children in 45 US states and 15 countries.

The PBC is a safe mobility tool for toddlers that consists of a rectangular frame with magnets and belt (Figure 1). Adults easily attach/detach the cane frames to the cane belt. The cane base slides along the floor, this contact provides the child with MVI/B safe mobility sensory feedback about the walking path, the cane frame protects direct bodily collisions with obstacles below the waist.

Prior blog posts have provided the results of single-subject studies of children with MVI/B aged two and older. These studies found that children with MVI/B and already ambulatory, improved in gait, posture and frequency of walking once wearing their PBCs (see blog posts by Ambrose-Zaken, 2019, 2020; Kersey, 2020; and McBride, 2020).

The purpose of this study was to examine the effects of wearing the belt cane by a toddler who was seventeen months with light perception only and not yet walking independently. His walking before and with the PBC was compared to his sighted twin brother in the same environments.


The researcher employed a single-subject repeated measures design. The twins were videoed walking independently in two locations, at two times, under different mobility conditions. The sighted twin's mobility condition was walking with normal indoor lighting. The twin who was blind with light perception walked under two mobility conditions in well-lit indoor settings; 1) walking without a PBC and 2) walking wearing a PBC. The first videos were taken in May 2019 in the Center for Discovery and Innovation lab on City College of New York (CCNY) campus and the second were taken in July 2019 at a shopping mall.


Seventeen-month-old twin boys were observed walking with their mother and father. One brother was identified as having some light perception due to optic nerve hypoplasia and bilateral retina coloboma. His family completed the intake questions. They described his motor skills as "having a hard time walking. His physical therapist indicated that he was afraid of walking". The participant’s family described his walking therapy as “keep encouraging him to walk.” Prior to entry into this study, his exposure to mobility tools consisted of a "push toy that was used at school". His family stated that when he was left to play on his own, he "just sits quietly” and indicated that they were seeking a belt cane "to allow him independence".

His sighted twin was typically developing with no disabilities. He was observed already walking independently in May. He had a wide-based gait, and did not yet run.


When the twins were walking without assistance, the number visible steps taken between pauses greater than 30 seconds or time between an adult providing walking assistance were counted as a video segment. Steps were defined as purposefully moving the foot forward or backwards. The length of video segments varied, therefore, the measure of steps per second was used. Step per second was obtained by dividing the total number of steps taken during the video segment by the total number of seconds of the video segment.

Title 17-month old twins (one blind, one sighted) steps per second two locations; Twin blind due to optic nerve hypolasia: Lab (no cane) 0.00, 0.05, 0.09, 0.00, 0.33, 0.00, 0.00, 0.00, 0.00, Lab w/belt cane 0.00, 0.00, 1.86, 0.33, 1.60, Mall w/belt cane 1.50, 1.78, 1.00, 1.78; twin fully sighted Mall (sighted) 1.5, 2.4, 2.5, Lab (sighted) 2.86, 2.00, 3.33, 2.50, 2.50, 3.00, 2.50, 2.73, 3.00, 3.00, 2.86, 3.00, 1.83, 3.00, 2.50, 3.50
Figure 2. Single subject step data


The participant who was blind was provided with a custom-fit PBC in May. While at the CCNY lab, the family was instructed in its use. The family was given the PBC usage guideline "wear the PBC most of the day, every day". Family reported that the participant who was blind with light perception was provided regular physical therapy sessions wearing his PBC, and wore his PBC during family outings to the shopping mall. They did not put his PBC on him at home.

Although the sighted participant was provided with no specialized equipment or instruction, from May through July, his independent walking practice continued unabated. He had full access to well-lit environments providing him with an abundance of safe mobility. During the May trials and the next three months, the sighted adults switched on the lights every day, all day providing him with constant access to well-lit environments. The sighted twin was allowed to complete all wake-time activities at home and elsewhere with full visual feedback of clear/blocked paths.

At the shopping mall in July, the two participants were videoed walking independently under safe mobility conditions; the sighted twin with benefit of well-lit environment, and the twin who was blind with consistent tactile path information resulting from wearing his PBC.


Figure 2 shows increased steps per second for both boys from May to July. Shortly after donning the PBC in May, the twin who was blind with light perception walked more steps per second wearing the PBC than when not wearing the PBC. The sighted brother walked more steps per second than his twin who was blind.

In July, the participant who was blind walked at a rate that was slower compared to his sighted twin brother. However, his steps per second were improved compared to when not wearing and when first wearing his PBC in May.

The sighted twin slightly increased his steps per second from May to July. In addition, his pace appeared to be more uniform when compared to his brother's pace.


The twin comparison allows us to understand the extent of the gross motor difference. At seventeen and twenty-months, the sighted twin was on target developmentally. He was walking well without adult assistance, but not yet running. His twin who was blind demonstrated delayed gross motor skills. At seventeen months, prior to donning the PBC he was exhibiting twelve-month gross motor skills, walking only with adult assistance.

When wearing his PBC, at seventeen and twenty-months the twin who was blind demonstrated improved gross motor skills. He achieved fifteen-month walking behaviors, walking alone with wide-based gait, but he was still delayed compared to his twin brother.

This study suggests that professionals and families should not wait until toddlers with MVI/B are able to walk to wear their PBCs. Toddlers who are MVI/B benefit from wearing developmentally appropriate safe mobility devices to encourage and enhance their independent walking. After minimal exposure to wearing his PBC, the twin who was blind had improved his gross motor development. This suggests that had he been provided with safe mobility also at home, like his sighted brother, his steps per second may have improved even more.


The difference in access to safe mobility is profound. The sighted toddler needed an adult to turn on the light switch to illuminate the walking path, as he cannot reach the light switch himself. Sighted toddlers are expected to rely on adults to turn the lights on for safe mobility and no one questions whether or not to provide this essential safe mobility support, turning the lights on, to them.

Blind children need adults to put on their safe mobility devices, too. For example, toddlers need adults to put them in their car seats, they need adults to hold their hands when crossing the street, and toddlers with MVI/B need adults to put their PBCs on for them.

Toddlers with MVI/B need their PBCs on as much as sighted toddlers need the lights on.

The only manner in which a blind person can obtain safe mobility is through the addition of consistent tactile path information. Fully-functioning adults who are blind can swing a hand-held cane back and forth with each step to achieve safe mobility.

Blind toddlers need safe mobility to thrive, but they are unable to use an adult cane for safe mobility, therefore they need an adult to put on their belt canes for them.

We need to provide all toddlers with MVI/B access to path information in a manner that makes sense to them. Pediatric belt canes provide consistent tactile path information about whether the path ahead is clear or blocked. That’s all and that's everything.

Twin who is blind being assisted by his dad, both hands held above his head, sighted twin walks on his own, arms down.
In May, twins walking prior to belt cane

Twin who is blind is walking wearing his cane, no adult holds or helps him, mother walks behind him. His twin brother being held back by his father.
In May, first independent steps wearing pediatric belt cane

Twin who is blind walks on his own, his physical therapist looks on.
In July, walking at the mall


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