The suggestions of causes resulting in idiopathic speech-language disorders have varied during decades and affected the terminology and diagnostic criteria. No particular characteristics are attributed to any type of developmental speech and language disorders. Speech sound errors are common in all developmental speech and language disorders. Consistent articulation errors have been thought to originate from speech motor problems, whereas the label dysphonology has been attached to variable and unstable speech sound errors with no detectable physiologic or physical association. It has been argued that motor impairment cannot explain that a child is capable of producing a specific sound in one condition, but not in another. The inconsistency of speech sound errors has been taken as a linguistic disorder and a deficiency to use the sounds as a part of the language system (Gibbon 1999).

Because of the difficulty in recognizing the pathophysiology of the speech sound errors the term articulation/phonology disorder (APD) has been used. The omissions and substitutions of speech sounds have been suggested to represent phonological, ie, linguistic, disorders, while distortions indicate articulatory problems, ie, consistent dysfunction of articulating speech organs. These errors probably origin from undifferentiated lingual gestures, and thus reflect delayed or deviant control of functionally independent regions of the tongue. The lack of differentiation of articulators has been documented by electropalatography (Gibbon 1999). The lack of differentiation of the tongue tip and blade from the movements of posterior part of the tongue, as well as the difficulty in controlling the lateral parts of the tongue in sagittal groove formation, is typical in APD. APD children also tend to lift the posterior part of the tongue, when only anterior lift is required. Undifferentiated tongue movement reflects insufficient spatial acuity of the articulators that is typical in immature articulation. However, the motor variability in producing speech sounds may also result in linguistic impairment in terms of phonological inconsistency of the speech sound system of the language (Gibbon 1999). Considering developmental speech sound errors the term speech sound disorder (SSD) is currently preferred because this fairly common developmental disorder may have antecedents in both articulatory (sensorimotor) and phonological (cognitive-linguistic) domains (Lewis et al 2006; McGrath et al 2007). It is considered to be clinically useful to subtype the children with SSD into those that present with concomitant language disorder and to those without it (Lewis et al 2006).

The phonetico-phonological symptoms of APD and SSD share common speech characteristics with developmental verbal dyspraxia (DVD), childhood apraxia of speech (CAS), or developmental apraxia of speech (DAS). DAS and CAS have been described as disorders of speech motor programming and control. In them, the behavioral characteristics are numerous, including inconsistent speech sound errors and dysprosody (Forrest 2003; Nijland et al 2003; Jacks et al 2006). The later developing consonants (eg, /l/, /r/, /s/) are typically omitted or substituted by early developing ones. The initial and final consonants are often omitted, the overall consonant accuracy is low and the production of consonant clusters and complex mono- and polysyllables is typically difficult (Jacks et al 2006). The vowels may also be distorted, but the distortion is not always eliminated by advancing age (Davis et al 2005). Children with CAS (DAS/DVD) often present with severe and long lasting unintelligibility of speech, and the treatment so far lacks generally accepted effective methods (Davis et al 1998; Jacks et al 2006).

In summary, the developmental disorders APD, SSD, DVD, CAS, and DAS share common characteristics and the terms seem to be used somewhat synonymously (cf. Gibbon 1999; Forrest 2003; Nijland et al 2003; Jacks et al 2006; McGrath et al 2007). APD, SSD, DVD, CAS, and DAS are idiopathic expressive speech disorders that may be included in developmental language impairment (DLI) or specific language impairment (SLI).

Even though there is so far no consensus on the diagnostic inclusion or exclusion criteria and definition of DVD (Forrest 2003), a consensus has been obtained about the definition of general developmental dyspraxia (Sanger et al 2006). It is typical that the child has not yet achieved the skills to perform complex motor functions (in the absence of muscular weakness, involuntary muscular movements, or deficient selective control of muscular functions or ataxic disability to activate correct motor patterns) appropriate for age (Sanger et al 2006). This definition fits also well in DVD, which may be taken as narrow band disorder among developmental dyspraxias.

Disorders of motor development associated with DLI and SLI are common, widely recognized and reported (Bishop et al 1987; Robinson 1991; Rintala et al 1998; Hill 1998; Webster et al 2006). Motor problems are found to be common also in association with reading disability, even in 60% of cases (Kaplan et al 1998; Viholainen et al 2006).

It is generally thought that the children start walking without support at the average age of 12 months. According to the WHO multicenter study (2006), 50% of the children have started to walk unassisted by the age of 12 months, about 25% by the age of 11 months, and 3%–10% by the age of 9–10 months. Very little attention, if at all, has been paid on speedy motor development in association with speech-language disorders. Even though speedy walking babies are less common in general population, they seem to be common among speech disordered children (Haapanen 2007). According to clinical observations, early walking seems to be familial also among those speech-language disordered children, particularly in children with expressive disorders that have started walking at typical age.

Haapanen (2007) has described a case series of 10 children with a particular developmental behavioral triad. They have unbalanced psychomotor development. The children have started to walk unassisted earlier than typical (at the latest by the age of 11 months), and they experience with expressive speech disorders resembling DAS and tongue movement dysfunction (lingual dysfunction with undifferentiated lingual movements resulting in dentoalveolar (ie, linguoalveolar) sound disorder. To name and describe them shortly, these children are here called SPEEDY babies (“Vauhtiveikot” in Finnish; Haapanen 2007) with SPEE referring to speech and DY to developmental dyspraxia or speech-language disorder such as developmental dysphasia, and dysfunction of the tongue.

The age of walking without support was not evenly distributed between the two diagnostic groups. Expressive SLI was significantly associated with earlier walking age according to Mann-Whitney U test (U = 126.00, p = 0.022). In the total group of 60 children, the ones with expressive speech production disorders (including children with mild ankyloglossia and impaired speech without diagnosed SLI) walked significantly earlier than the ones with speech comprehension problems (Mann-Whitney U test, U = 195.5, p = 0.013).

Counting out the children who began walking at the age of 11 or 12 months, 10/16 (63 %) children were left, who had expressive speech problems and walked without support before the age of 11 months. Also 6/16 (37%) children were left who had expressive speech impairment, and who walked at the age of 13 months or later. None of those children that had receptive or mixed SLI belonged to the earlier walking group. The difference was statistically significant (Fisher’s exact test, p = 0.035).

The milestones of gross motor development are reported in terms of starting to walk without support. Data of the age at which the first unassisted steps were made and when the occurrence of the first words and sentences occurred were obtained by the parents’ reports and the carefully made baby clinic recordings. Parental information of developmental milestones must be taken with caution. There are no clear criteria to recognize the first steps, words or sentences. However, parents typically note those milestones that are often emotionally charged so that they write them into baby books that are common in Finnish families. Parents tend to remember the developmental milestones of walking very well, even when the child is 3-years-old, and still fairly well, when the child is 5-years-old. However, recall of first words is less exact (Majnemer and Rosenblatt 1994). In these children, parents’ reports of developmental milestones were confirmed by health care registrations. Although the children were reported skilled in many rough motor functions, such as climbing, running, bicycling, and various sports, data were not collected because of the difficulties of obtaining reliable data.

A behavioral pattern of unbalanced motor and speech development is typical to the present children and similar to those described earlier by Haapanen (2007). The children presented with a triad of speedy unsupported walking ability associated with expressive speech impairment including inconsistent error characteristics typical of developmental verbal dyspraxia, as well as stable misarticulations. The consistent speech sound production errors were found to result from lingual dysfunction, in terms of the inability to lift and broaden the tip of the tongue on the upper lip or alveolar ridge and the deficiency in the control of lateral borders of the tongue. The present misarticulations resemble those due to undifferentiated lingual gestures that were described by Gibbon (1999). One of the present children could not produce low back vowels. Misarticulations of dentoalveolars and low vowels probably indicate difficulty in lowering the body and back of the tongue. Typically consistent misarticulations occurred in the late developing alveolar, nonnasal continuous consonants (/s/, /l/, /r/). They were consistently distorted, but they also underwent inconsistent dysphonological processes such as omissions, substitutions, assimilations or reversals. No labial or velopharyngeal dysfunction occurred even though labials of velar stop consonants were inconsistently correctly produced/omitted/substituted or changed by other processes typical of verbal dyspraxia. In the case of two children, the neuropsychological discrepancy criteria that is used when diagnosing SLI (eg, DSM IV, ICD 10) was not fulfilled, which is not, however, necessary in diagnosing verbal dyspraxia (cf. Forrest 2003). It may not be possible to differentiate between DVD and SSD, that may occur with or without coexisting language disorder (Lewis et al 2006).

Consistent lingual dysfunction that occurred in the present children and in those described by Haapanen (2007) has not so far been reported as typical of verbal dyspraxia. However, the lingual dysfunction found in SPEEDY babies may be similar to tongue motor difficulties, of which Kent (1992) has stated that speech motor variability resulting in phonetic variability of speech sounds can be so great that it results in an apparent variability in phonology, ie, in dysphonology. Concomitant dysarthria was not diagnosed, even though not fully excluded. Murdoch and colleagues (1995) have found that children with DVD may have weaker lingual musculature and exhibit significantly reduced tongue strength endurance than the controls. This may indicate coexisting dysarthria in DVD children.

Even though the present children experienced with only a few consistent misarticulations, their speech disorder can be regarded as moderate or severe because of particularly inconsistent sound substitutions, omissions and assimilations. The /r/, /s/, and /l/ sounds are sounds that develop late and are often misarticulated in children even at the preschool age (Luotonen 1995). The Finnish /r/ sound is generally found very difficult to produce because of anterior tongue tip vibration necessary for normative /r/. The persisting /r/ sound disorders in Finnish children have been taken as a marker of verbal dyspraxia (Qvarnström et al 1993). The difference between the present SPEEDY babies and typically developing children is, however, their dysphonology which is rare in the common population (Tomblin et al 1997).

An interesting finding is that the present SPEEDY babies, as well as those described by Haapanen (2007) seem to be physically healthy. Recurrent middle ear infections and respiratory allergies are uncommon among them. However, the children are prone to social problems, because of unclear speech. They also can be taken as troublemakers because of their motor activity that results in demands for continuous attention to their physical safety, particularly in early infancy.

Since speedy rough motor development seems to be clustered in some children with idiopathic expressive speech impairment, particularly with speech characteristics typical of developmental verbal dyspraxia and consistent lingual dysfunction, it seems justifiable to consider those behavioral phenomena occurring as a syndrome. It is obvious that early walking does not explain the speech disorder, but there may be an inherited link between those developmental characteristics. Interestingly, according to our preliminary observations, children that start walking early independently seem to be fairly common among speech disordered children, particularly among those with expressive speech-language disorders. In the present preliminary series of 60 consecutive cases, none of the children who had receptive SLI walked before the age of 11 months. On the contrary, speedy motor development seems to be more often associated with delayed achievement of expressive speech considered normal by articulation or phonolgy. An interesting question arises: does biodiversity among human beings also appear in terms of bipolarity of the achievement of behavioral developmental milestones?

Speedy walking development also seems to be common in the family members of both SPEEDY babies and of those speech-language disordered children, who have started to walk at typical age. The children that start walking at typical age, but present with expressive SLI seem to have significantly more often relatives with speedy walking than the children with receptive SLI. This has not so far evoked any attention. Instead, much attention has been paid on familial co-occurrence of speech/language and reading/writing disorders (Stormswold 1998; Barry et al 2007), which also are common in SPEEDY babies, both in the present children and in those presented by Haapanen (2007). However, speech or reading and writing disorders do not seem to be significantly associated with either of the SLI subtypes, whether expressive or receptive. It seems that dyslexia may not be as seemingly associated with early independent walking as expressive speech disorders seem to be. It is obvious that the association between the timetable of independent walking and speech and learning development warrants further studies.

Albeit developmental disorders of motor functions have been studied much (Hill 1998; Webster et al 2006), hardly any attention is paid on atypically speedy motor development in association with speech-language disorders. The speech-language disordered population is very heterogeneous. An unclear phenotypic diagnostics obscures the study populations and slow down accumulation of knowledge of this population (SLI Consortium 2004). In order to gather phenotypic and genotypic information and to design recognition and rehabilitation strategies of individuals with communication disorders, it is important to try to search for particular developmental and behavioral characteristics that seem to cluster.

To delineate and sharpen the clinical picture of SPEEDY babies, it is worth further studies to eg, examine how common speedy unassisted walking is among speech-language disordered population, how do the behavioral characteristics vary in different ages, how variable is their cognitive profile, what are their fine motor functions like. Speedy rough motor and postural control development does not guarantee skilled fine motor functions, such as eg, eye-hand motor functions (Viholainen et al 2006).