The emergence of a syndrome-specific personality profile in young children with Down syndrome
For decades, researchers and practitioners have attempted to find evidence for a personality stereotype in individuals with Down syndrome that includes a pleasant, affectionate, and passive behaviour style. However, a more nuanced exploration of personality-motivation in Down syndrome reveals complexity beyond this pleasant stereotype, including reports of a less persistent motivational orientation and an over-reliance on social behaviours during cognitively-challenging tasks. It is hypothesised that the personality-motivation profile observed in individuals with Down syndrome emerges as a result of the cross-domain relations between more primary (cognitive, social-emotional) aspects of the Down syndrome behavioural phenotype. Young children with Down syndrome show a general profile of delays in the development of instrumental thinking coupled with emerging relative strengths in social-emotional functioning. If it is true that a less persistent motivational orientation emerges as a secondary phenotypic result of more primary strengths in social functioning and deficits in instrumental (means-end) thinking, it may be possible to alter the developmental trajectory of this personality-motivation profile with targeted and time-sensitive intervention. Implications for intervention planning are discussed.
Fidler, D. (2006) The emergence of a syndrome-specific personality profile in young children with Down syndrome. Down Syndrome Research and Practice, 10(2), 53-60. doi:10.3104/reprints.305
Many areas of the Down syndrome behavioural phenotype have been well researched, with strengths and weaknesses identified in information processing, social functioning, motor development, and language (Byrne, Buckley, MacDonald & Bird, 1995; Fidler, Hepburn, Mankin & Rogers, 2005; Gibbs & Thorpe, 1983; Hesketh & Chapman, 1998; Jarrold & Baddeley, 1997; Jarrold, Baddeley & Hewes, 1999; Jobling, 1998; Klein & Mervis, 1999; Laws, 1998; Miller & Leddy, 1999; Mon-Williams et al., 2001; Rodgers, 1987; Rosner, Hodapp, Fidler, Dykens & Sagun, 2004; Sigman & Ruskin, 1999; Wishart & Johnston, 1990; Wang & Bellugi, 1994). Another area of potential importance in the Down syndrome behavioural phenotype relates to the personality-motivational style.
For decades, researchers and practitioners have attempted to describe commonalities in personality style among individuals with Down syndrome, with some arguing for a stereotype involving a pleasant, affectionate, and passive personality style (Gibbs & Thorpe, 1983; Rodgers, 1987). This stereotype has been supported by studies of parent perception of children with Down syndrome, where in one study, over 50% of 11 year old children with Down syndrome were described as "affectionate", "lovable," "nice," and "getting on well with other people," (Carr, 1995). A large percentage of the children in this study were also described as "cheerful", "generous", and "fun" (Carr, 1995). There are also reports of increased positive mood and predictability in behaviour in individuals with Down syndrome, supporting the more positive pleasant aspects of the personality stereotype, as well as reports of lower activity levels, less persistence, and more distractibility than other children, supporting the more passive aspects of the stereotype (Gunn & Cuskelly, 1991).
However, a more nuanced exploration of personality-motivation in Down syndrome reveals great complexity in personality development and motivational style over time. In addition to these positive perceptions of personality in individuals with Down syndrome, other research reports have described individuals with Down syndrome as showing a specific motivational orientation involving lower levels of task persistence and higher levels of off-task social behaviours (Kasari & Freeman, 2001; Landry & Chapieski, 1990; Pitcairn & Wishart, 1994; Ruskin, Kasari, Mundy & Sigman, 1994; Vlachou & Farrell, 2000). This lowered persistence is sometimes complemented by a stubborn or strong willed personality streak, also described in studies of temperament in Down syndrome (Carr, 1995; Gibson, 1978).
Though they have not received the same amount of attention from researchers as more positive personality dimensions, poor persistence and a stubborn temperament may have far-reaching implications for developmental outcomes in Down syndrome. Some researchers suggest that these characteristics contribute to some of the inconsistency in developmental performances observed in young children with Down syndrome. Several studies have reported that young children with Down syndrome ages 6 months to 4 years show significant regressions on the same testing battery across sessions (Wishart & Duffy, 1990; Morss, 1983), and it has been noted that many of these regressions result from children's refusal to engage in tasks (Pitcairn & Wishart, 1994; Wishart & Duffy, 1990).
In fact, this phenomenon has been quantified by researchers interested in exploring motivational performance in children with Down syndrome. Jennifer Wishart and her colleagues have observed that, when faced with cognitive challenges in laboratory settings, children with Down syndrome often avoid tasks with both positive and negative behaviours more frequently than other children (Wishart, 1996). In young children, these behaviours can include refusing to look at a task, struggling out of a chair, or sudden crying behaviour (Wishart & Bower, 1984). Older children have been shown to engage the experimenter with off-task social behaviour that distracts them from the task at hand (Pitcairn & Wishart, 1994). These social behaviours might include directing the experimenter's attention to something else and/or using 'party trick' behaviours (clapping hands, directing the experimenter's attention away from the task). Wishart (1996) describes these "cognitive avoidant" or "quitting out" behaviours as a unique feature in the performance of children with Down syndrome on developmental assessments.
Beyond the implications for assessment in research settings, it may be that this weak motivational orientation impacts other areas of functioning in Down syndrome, including performance in educational and intervention settings. Wishart (1996) argues that, "[f]rom a very early age, it would appear that the Down syndrome children are avoiding opportunities for learning new skills, making poor use of skills that are acquired, and failing to consolidate skills into their repertoires" (Wishart, 1996). If this is true, then understanding personality-motivational orientation in individuals with Down syndrome may offer researchers a unique opportunity to improve the effectiveness of intervention and educational programming in individuals with Down syndrome. This may hold for educational programming in school settings for children and adolescents who have already developed this profile, and it may especially be relevant in early intervention settings, where it may be possible to try to prevent this profile from ever emerging. In order to plan effective intervention, it may be important to understand how this personality profile comes to be.
Exploring the origins of the personality-motivation profile in Down syndrome
How does this personality profile involving positive mood and sociability coupled with lowered persistence and 'quitting out' behaviours emerge and develop over time? Unlike other aspects of the Down syndrome behavioural phenotype, which may have their origins in the intersection between genetics and brain development (for example, stronger visual processing and weaker verbal processing; Frangou et al., 1997; Jarrold, Baddeley & Hewes, 1999; Klein & Mervis, 1999; Laws, 1998; Pinter et al., 2001; Pueschel, Gallagher, Zartler & Pezzullo , 1987 ; Wang & Bellugi, 1994), it may be that this personality profile emerges as a 'secondary phenotypic' outcome. That is, the personality-motivation profile observed in individuals with Down syndrome may emerge as a result of the cross-domain relations between more primary (cognitive, social-emotional) aspects of the Down syndrome behavioural phenotype.
In the following sections, we will explore the intersection between early strengths in social functioning and deficits in cognition and means-end thinking, and how together they may contribute to the emergence of a personality profile that involves an over-reliance on an endearing social style at the expense of a more persistent motivational orientation. We first explore two 'primary phenotypic' behavioural outcomes associated with early development in Down syndrome: the early cognitive phenotype and the early social-emotional phenotype. We will then explore the cross-domain relations between social and cognitive functioning that may predispose children with Down syndrome to adopt the specific personality-motivation style often observed in this population.
Primary phenotypic outcomes: Cognition
In typically developing infants, one of the most important early cognitive achievements is the development of means-end, or instrumental thinking (Bjorklund, 2000; Piaget, 1952). Means-end thinking begins to develop during the first 2 to 8 months of life. In its earliest forms, means-end thinking generally involves linking a chain of behaviours together as a means to reach an end-state, for example pulling on a string to obtain a toy that is attached to the string. For example, typically developing 2- to 8- month old infants show contingency learning skills that involve learning to move certain body parts (such as pulling their arm) as a means to achieving reinforcement outcomes (picture displays and music; Lewis, Alessandri & Sullivan, 1990). At approximately 8 months, infants discover how manual skills may be used to achieve new goals. New behaviours, such as reaching and grasping, open up a whole set of different goals, and these new strategies are used as a means to achieve desired end states.
However, the existing literature on the development of means-end thinking in infants and toddlers with Down syndrome suggests that this is an area of major challenge. In a study of contingency learning (an early version of cause and effect/means-end thinking), three-month-old infants with Down syndrome showed equivalent performances to typical infants on contingent learning tasks that involved reinforcement for their own leg kicking, including equivalent initial learning, learning speed, and retention (Ohr & Fagen, 1991). However, the same research team (Ohr & Fagen, 1994) reported that by 9 months, the same cohort of infants with Down syndrome demonstrated significantly impaired contingency learning relative to typically developing infants. The authors of this series of studies suggested that there is a decline in contingency learning and conditionability in infants with Down syndrome over the first year of life. If means-end thinking relies in part on contingency learning, this could be early evidence of atypical development of means-end thinking that is specific to the population of infants with Down syndrome.
Further evidence for atypical development of instrumental thinking can be found in a study of sensorimotor stage transitioning in infants with Down syndrome (Uzgiris & Hunt, 1979). Dunst (1988) found that infants with Down syndrome take longer to move from means-end stage V (e.g. pulling a string to obtain a toy) to means-end stage VI (e.g. showing intention while putting a necklace in a cup) than typically developing infants. But this slower stage transitioning was not evident in other areas, such as object permanence, gestural imitation, and causality. Delays in the emergence of more advanced means-end thinking in infancy may be evidence of specific impairments in aspects of problem solving skills in Down syndrome.
Means-end thinking has also been found to be unrelated to other domains of sensorimotor development, including object permanence, vocal imitation, gestural imitation, operational causality, spatial relationships, and object schemes in infants with Down syndrome (Dunst & Rheingrover, 1982). This is evidence of a lack of stage congruence between means-end performance and performances in these other aspects of sensorimotor functioning. Others report no associations between means-end performances at 5 months and later at 13, 15, 18, and 24 months in infants with Down syndrome (Cicchetti & Mans-Wagener, 1987). In contrast, strong associations are observed in other sensorimotor areas, such as vocal imitation, object permanence, and spatial relations. These findings suggest that while many other areas of sensorimotor functioning develop in concert with one another in Down syndrome, means-end thinking follows an atypical and slower developmental trajectory.
Beyond infancy, there is also indirect evidence that young children with Down syndrome show continued delays in the means-end (instrumental) component of problem solving. Ruskin et al., (1994) reported that toddlers with Down syndrome in their study showed significantly shorter chains of continuous goal-directed mastery behaviours with a cause and effect toy (e.g. fitting blocks through corresponding holes) than MA-matched typically developing children. This suggests that toddlers with Down syndrome continue to have difficulty putting together chains of behaviour as a means to reaching a particular end. Similarly, our team (Fidler, Hepburn, Mankin & Rogers, 2005) found that toddlers with Down syndrome showed less optimal strategies on an object retrieval problem solving task (i.e., obtaining a desired item from under a plastic box) than MA-matched typically developing toddlers and toddlers with other developmental disabilities.
Thus, deficits in the building blocks of instrumental or strategic thinking have been observed from the earliest stages of the development of means-end thinking, and in many different types of laboratory settings. But the impact of these findings may go beyond observing performances on instrumental tasks in laboratory settings. Young children with Down syndrome show lower levels of causality pleasure, showing fewer positive facial displays during goal-directed mastery behaviours than the comparison group of typically developing children (Ruskin et al., 1994). This suggests that children with Down syndrome not only show deficits in instrumental thinking, but they also do not show usual amount of enjoyment and pleasure when engaging in tasks that involve means-end or strategic thinking. This may have important implications for developing a motivational orientation that involves engaging with new and challenging tasks.
Primary phenotypic outcomes: Social functioning
Delays in the development of instrumental thinking in young children with Down syndrome are complemented by an emerging relative strength in social-emotional functioning. By the time they reach the age of three, many children with Down syndrome already show quantifiable strengths in social functioning as measured by the Vineland Adaptive Behaviour Scales (Fidler, Hepburn & Rogers, 2006). Our team has also reported that early orienting and engagement behaviours in young children with Down syndrome may be a specific area of developmental competence that grows at a faster pace than others areas of development (e.g., emotion regulation, motor functioning). While some studies report no significant temperament differences between infants with Down syndrome and typical infants (Ohr & Fagen, 1994; Vaughn, Conteras & Seifer, 1994), other studies report that young children with Down syndrome are of more positive mood, more rhythmic, and less intense than CA-matched children (Gunn & Berry, 1985).
There is also evidence of emerging areas of competence within some aspects of social functioning in infancy in Down syndrome. Early looking behaviour (Crown et al., 1992; Gunn et al., 1982), vocalising (Legerstee, Bowman & Fels, 1992), and facial imitation in infancy (Heiman & Ullstadius, 1999) have been identified as evidence of social relatedness in the first year of life. Though the onset of looking behaviour (at parent) is delayed during the first few months of development, by the middle of the first year, infants with Down syndrome may show increased looking behaviour toward their parent relative to other infants (Crown et al., 1992; Gunn et al., 1982). Three issues are notable in these behavioural findings. First, these behaviours may be evidence of the competent achievement of primary intersubjective milestones in infancy, wherein infants with Down syndrome develop behaviours that are evidence of core social relatedness; but these strengths may not translate into competence in all areas of subsequent social development. Second, looking behaviour for social purposes does not seem to translate into looking behaviour for instrumental purposes, as young children with Down syndrome show lesser amounts of social referencing than other children at similar developmental levels (Kasari et al., 1995; Walden et al., 1991). Third, while many young children with Down syndrome show these early behaviours, there is a subgroup of children who do not, and these children may present with comorbid psychiatric diagnoses, such as autism.
Some aspects of social behaviour in toddlers and preschoolers with Down syndrome also seem to develop with competence. Young children with Down syndrome show appropriate levels of joint attention for their developmental level (Mundy et al., 1988; Sigman & Ruskin, 1999), more play acts than other children at similar developmental levels (Sigman & Ruskin, 1999), and they attend to the emotional signals (Sigman & Ruskin, 1999) and initiations of others (Bressanutti, Sachs & Mahoney, 1992). In terms of attachment, there is some disagreement regarding whether children with Down syndrome show higher levels of insecure attachment (Berry, Gunn & Andrews, 1980; Vaughn et al., 1994), though questions have been raised regarding the appropriateness of the Strange Situation paradigm for children with developmental delays.
In addition to the development of core relatedness behaviours in young children with Down syndrome, there may be some uniqueness to the development of emotional displays as well. By the time they reach middle childhood, children with Down syndrome show more frequent smiling behaviour than other children with developmental disabilities (Fidler, Barrett & Most, 2005). Infants with Down syndrome were originally thought to show more muted emotional signalling relative to other infants (Berger & Cunningham, 1986; Buckhalt, Rutherford & Goldberg, 1978; Cicchetti & Sroufe, 1978). However, more frequent muted signals seem to happen in the context of appropriate levels of high intensity smiles (Kasari et al., 1990; Knieps et al., 1994). This suggests that there may be increased positive emotional signalling during the earliest years of development in young children with Down syndrome as well.
Finally, our team has also recently reported emerging competence in social functioning in the form of faster developmental rates in certain areas. In one study where infants with Down syndrome were assessed with the Bayley Scales of Infant Development at 12 and then 30 months, children with Down syndrome made greater gains in the Orientation/Engagement domains than they did in other domains including cognition and motor functioning (Fidler, Most, Booth-LaForce & Kelly, 2005). In addition, growth in the Orientation/Engagement domain of the Bayley was significantly more rapid in the Down syndrome group than in an MA-matched group of children with idiopathic developmental delays. At Time 1, children in both groups showed mean percentile scores in the 37 th percentile. However, by Time 2, the Down syndrome group showed mean percentile scores in the 58 th percentile (SD = 13.32), while mean comparison group scores showed an average in the 42 nd percentile (SD = 18.85). This is an average gain of 20 percentile points in the Down syndrome group. In comparison, the gains made by the comparison group children were more modest - a mean change of roughly 5 percentile points, which is approximately 15 percentile points or 75% less than the mean gain made by the Down syndrome group.
In addition, within-individual comparisons in this study suggested that greater gains were observed in Orientation/Engagement scores in comparison with other aspects of social-emotional functioning, such as performance in the Emotion Regulation of the Bayley. This suggests that the early strengths in social-emotional functioning are not domain general, but may be specific to the development of some aspects of primary intersubjectivity. Taken together, the results from this recent study contribute to larger body of literature supporting the notion that early orienting and engagement behaviours in young children with Down syndrome may be a specific area of developmental competence that grows at a faster pace than others areas of development.
Thus, young children with Down syndrome seem to show a general profile of delays in the development of instrumental thinking, coupled with emerging relative strengths in social-emotional functioning. In the next section, we explore an example of the manifestation of the difference in social versus instrumental competence in young children with Down syndrome: a split between requesting and joint attention behaviours in toddlers with Down syndrome.
Social/instrumental split in the emergence of intentional communication in Down syndrome
As early cognitive and social skills are emerging, they intersect with the development of nonverbal communication skills. When typically developing infants reach the ages of 9-13 months, they begin to use intentional communication in the form of joint attention and requesting. However, an important difference is observed in the nature of intentional communication in children with Down syndrome versus typically developing children or even other children with developmental disabilities. This difference relates to the emergence of nonverbal communication for social purposes and the emergence of nonverbal communication for instrumental purposes (as a means to an end).
Several studies have shown that early nonverbal social communication (e.g. joint attention) behaviours emerge as a relative strength in young children with Down syndrome, while early nonverbal instrumental communication (e.g. requesting) behaviours emerge as an area of relative weakness (Fidler, Philofsky, Hepburn & Rogers, in press; Mundy, Sigman, Kasari & Yirmiya, 1988; Mundy, Kasari, Sigman & Ruskin, 1995; Wetherby, Yonclas & Bryan, 1989). For example, our team showed significantly fewer overall instrumental requests and low-level instrumental requests than a group of MA-matched typically developing infants and toddlers on the Early Social Communication Scales (Fidler, Philofsky, Hepburn & Rogers, in press). A split between instrumental gesturing (gesturing as a means to an end) and social gesturing (gesturing for the sake of social sharing) was evidenced in the dissociation between nonverbal requesting and joint attention skills in the Down syndrome group.
However, is interesting to note that this requesting deficit seemed to be specific to instrumental requesting situations in our study (Fidler, Philofsky, Hepburn & Rogers, in press). In fact, young children with Down syndrome in our study showed marginally more requests during social routines. This suggests that the deficit in requesting in Down syndrome did not result from difficulties with performing specific acts associated with requesting (eye contact or reaching), but may have to do with using those behaviours as a means to an end, and to regulate another's behaviour for instrumental purposes. In addition, our study reported an association between instrumental requesting behaviour and problem solving performances in young children with Down syndrome. This suggests that the deficit in requesting behaviour previously reported in toddlers with Down syndrome may be a function of poor means end functioning, and not deficits in communication.
Thus, there is strong evidence that the earliest years of life for many individuals with Down syndrome involve an emerging strength in social functioning (including strengths in the emergence of nonverbal social communication), and deficits in the development of means-end or strategic thinking (including deficits in the emergence of nonverbal instrumental communication). It is hypothesised here that the cross-domain relations between these two developing areas of functioning contribute to the emergence of a specific personality-motivation orientation, including poorer persistence and an over-reliance on social strategies.
Poorer persistence could be the indirect result of emerging difficulties with instrumental and strategic thinking during infancy in Down syndrome. Toddlers and preschoolers with Down syndrome who quit out of tasks or abandon challenging situations may be doing so because they simply are not able to generate new, more viable strategies to complete the task. That is, they have difficulty coming up with different options that serve as a means to the end of completing the task. Thus, a more passive and less persistence personality-motivation style could be directly linked to emerging primary deficits in instrumental reasoning, and more generally, in cognition.
Furthermore, in those instances when children with Down syndrome are not able to generate new strategies that can serve as a means to an end, it may be that what comes most naturally to them is to recruit their strengths in social skills. As a result, they may develop a style that involves responding to challenging situations with charming or socially engaging behaviours that, ultimately, take them (and their social partner) off task. Or, they may rely on another social strategy, such as recruiting help from a social partner in order to help them complete a task, which has also been demonstrated in several laboratory studies (Fidler, Hepburn, Mankin & Rogers, 2005; Kasari & Freeman, 2001). In either case, the coupling of poor strategic thinking and strengths in social relatedness is hypothesised to lead to the less persistent and overly social personality-motivational orientation observed in this population. Even in the cases when social strategies are not selected, rather than generating a new strategy for resolving a problem at hand, stubborn behaviour suggests that children with Down syndrome get stuck on one particular strategy or approach and can not get 'unstuck' from it.
If it is true that a less persistent motivational orientation emerges as a secondary phenotypic result of more primary strengths in social functioning and deficits in instrumental (means-end) thinking, it may be possible to alter the developmental trajectory of this personality-motivation profile with targeted and time-sensitive intervention. For example, it may be possible to focus on strengthening early means-end or strategic thinking in very young children with Down syndrome in order to prevent the deceleration of these skills that leads to a split in social and instrumental functioning by the time that intentional communication emerges. Addressing the development of instrumental thinking at this early stage may help to promote a more adaptive personality-motivation style in later early childhood and beyond.
There are several ways to potentially approach this type of intervention. For example, it may be possible to strengthen means-end thinking by targeting early instrumental requesting behaviour when a toddler with Down syndrome reaches the mental age of 9-13 months. This approach may be particularly preferable in that it is mediated by social signalling, thus making it a more learnable entry point than targeting cause and effect thinking through toys or other non-social stimuli. It may also be possible to shape different instrumental requesting signals to encourage flexibility and generalisability across various situations. Though targeting requesting in young children with Down syndrome remains only a hypothetical entry point, there is evidence mounting at this point to suggest that at the very least, this may be a potentially effective entry-point for intervention.
Another important area for intervention may relate to the strengthening of behaviour chaining in young children with Down syndrome. There is evidence that young children with Down syndrome do not effectively chain sequences of goal-directed behaviours during play and non-social instrumental tasks (Ruskin et al., 1994). It may be that strategising difficulties are compounded by the cognitive load involved in chaining together a sequence of behaviours. Often, more difficult real life problem solving tasks involve more than one behaviour in a sequence in order to solve the problem effectively (e.g., find keys, select appropriate key, unlock door). Ideas for intervention to strengthen these skills are likely to be useful, constructing easy-to-solve problem solving tasks that require more than one step and encouraging practice in assisted settings.
In exploring the origins of the personality-motivation orientation in individuals with Down syndrome, it may be possible to preserve the more positive aspects of the profile (social motivation), while targeting the maladaptive aspects of the profile (quitting out behaviour). Though the suggested techniques remain unproven by empirical studies at this time, continued research in this area may yield more definitive support for these suggestions. Even given this caveat, it is likely that promoting more optimal motivational development in individuals with Down syndrome with targeted and time-sensitive techniques will be effective, and may impact development beyond simply improving adaptation. Helping young children with Down syndrome to recognise their own ability to generate effective strategies may lead to improved instrumental functioning, and may serve to improve academic performance, independence skills, and outcomes in adulthood.
Deborah J. Fidler, Ph.D. • 102 Gifford Building, 502 West Lake Street, Colorado State University, Fort Collins, CO, 80523. • Deborah.Fidler@colostate.edu.
- Berger, J. & Cunningham, C.C. (1986). Aspects of early social smiling by infants with Down's syndrome. Child: Care, Health and Development, 12 , 13-24.
- Berry, P., Gunn, P. & Andrews, R. (1980). Behaviour of Down syndrome infants in a strange situation. American Journal of Mental Deficiency, 85 , 213-218.
- Bjorklund, D.F. (2000). Children's Thinking: Developmental Function and Individual Differences. Belmont, CA: Wadsworth.
- Bressanutti, L., Sachs, J. & Mahoney, G. (1992). Predictors of young children's compliance to maternal behaviour requests. International Journal of Cognitive Education and Mediated Learning, 2 , 198-209.
- Buckhalt, J.A., Rutherford, R.B. & Goldberg, K.E. (1978). Verbal and nonverbal interaction of mothers with their Down's syndrome and nonretarded infants. American Journal on Mental Deficiency, 82 , 337-343.
- Byrne, A., Buckley, S., MacDonald, J. & Bird, G. (1995). Investigating the literacy, language, and memory skills of children with Down's syndrome. Down's Syndrome: Research and Practice, 3 , 53-58. [Open Access Full Text]
- Carr, J. (1995). Down's Syndrome: Children Growing Up. Cambridge: Cambridge University Press.
- Cicchetti, D. & Mans-Wagener, L. (1987). Sequences, stages, and structures in the organization of cognitive development in infants with Down syndrome. In I.C. Uzgiris & J.M. Hunt, (Eds.), Infant Performance and Experience: New Findings with the Ordinal Scales, (pp. 281-310) . Urbana-Champaign IL: University of Illinois Press.
- Cicchetti, D. & Sroufe, L.A. (1978). An organizational view of affect: Illustration from the study of Down's syndrome infants. In M. Lewis & L.A. Rosenbaum, (Eds.), The Development of Affect. New York: Plenum Press.
- Crown, C.L., Feldstein, S., Jasnow, M.D. & Beebe, B. (1992). Down's syndrome and infant gaze: gaze behavior of Down's syndrome and nondelayed infants in interactions with their mothers. European Journal of Child and Adolescent Psychiatry: Acta Paedopsychiatrica, 55, 51-55.
- Dunst, C. (1988). Stage transitioning in the sensorimotor development in Down's syndrome infants. Journal of Mental Deficiency Research, 32, 405-410.
- Fidler, D.J., Barrett, K.C. & Most, D.E. (in press). Age-related differences in smiling and personality in Down syndrome. Journal of Developmental and Physical Disabilities.
- Fidler, D.J., Hepburn, S., Mankin, G. & Rogers, S. (2005). Praxis skills in young children with Down syndrome, other developmental disabilities, and typically developing children. American Journal of Occupational Therapy, 59 , 129-138 .
- Fidler, D.J., Hepburn, S. & Rogers, S. (2006). Early learning and adaptive behaviour in toddlers with Down syndrome: Evidence for an emerging behavioural phenotype? Down Syndrome: Research and Practice, 9(3), 37-44. [Read Online]
- Fidler, D.J., Most, D.E., Booth-LaForce, C. & Kelly, J. (2005). Emerging social strengths in young children with Down syndrome at 12 and 30 months. Manuscript under review.
- Fidler, D.J., Philofsky, A., Hepburn, S.L. & Rogers, S.J. (in press). Nonverbal requesting and problem solving in young children with Down syndrome. American Journal on Mental Retardation.
- Frangou, S., Aylward, E., Warren, A., Sharma, T., Barta, P. & Pearlson, G. (1997). Small planum temporale volume in Down's syndrome: A volumetric MRI study. American Journal of Psychiatry, 154, 1424-1429.
- Gibbs, M.V. & Thorpe, J.G. (1983). Personality stereotype of noninstitutionalized Down Syndrome children. American Journal of Mental Deficiency, 87 , 601-605.
- Gibson, D. (1978). Down's Syndrome: The Psychology of Mongolism. Cambridge: Cambridge University Press.
- Gunn, P., Berry, P. & Andrews, R.J. (1982). Looking behaviour of Down syndrome infants. American Journal of Mental Deficiency, 87, 344-347.
- Gunn, P. & Cuskelly, M. (1991). Down syndrome temperament: the stereotype at middle childhood and adolescence. International Journal of Disability, Development, and Education, 38 , 59-70.
- Hesketh, L.J. & Chapman, R.S. (1998). Verb use by individuals with Down syndrome. American Journal on Mental Retardation, 103 , 288-304.
- Heiman, M. & Ullstadius, E. (1999). Neonatal imitation and imitation among children with autism and Down's syndrome. In J. Nadel & G. Butterworth, (Eds.), Imitation in Infancy, (pp. 235-253). Cambridge: Cambridge University Press.
- Jarrold, C., & Baddeley, A.D. (1997). Short-term memory for verbal and visuospatial information in Down's syndrome. Cognitive Neuropsychiatry, 2 , 101-122.
- Jarrold, C., Baddeley, A. D. & Hewes, A. K. (1999). Genetically dissociated components of working memory: Evidence from Down's and Williams syndrome. Neuropsychologia, 37 , 637-651.
- Jobling, A. (1998). Motor development in school-aged children with Down syndrome: A longitudinal perspective. International Journal of Disability, Development and Education, 45 , 283-293.
- Kasari, C. & Freeman, S.F.N. (2001). Task-related social behaviour in children with Down syndrome. American Journal on Mental Retardation, 106 , 253-264.
- Kasari, C., Freeman, S., Mundy, P. & Sigman, M.D. (1995). Attention regulation by children with Down syndrome: Coordinated joint attention and social referencing looks. American Journal on Mental Retardation, 100, 128-136.
- Kasari, C., Mundy, P., Yirmiya, N. & Sigman, M. (1990). Affect and attention in children with Down syndrome. American Journal on Mental Retardation, 95, 55-67.
- Klein, B.P. & Mervis, C.B. (1999). Contrasting patterns of cognitive abilities of 9- and 10- year-olds with Williams syndrome or Down syndrome. Developmental Neuropsychology, 16 , 177-196.
- Knieps, L.J., Walden, T.A., & Baxter, A. (1994). Affective expressions of toddlers with and without Down syndrome in a social referencing context. American Journal on Mental Retardation, 99, 301-312.
- Landry, S.H. & Chapieski, M.L. (1990). Joint attention and infant toy exploration: Effects of Down syndrome and prematurity. Child Development, 60 , 103-118.
- Laws, G. (1998). The use of nonword repetition as a test of phonological memory in children with Down syndrome. Journal of Child Psychology and Psychiatry and Allied Disciplines, 39 , 1119-1130.
- Legerstee, M., Bowman, T.G. & Fels, S. (1992). People and objects affect the quality of vocalizations in infants with Down syndrome. Early Development and Parenting, 1 , 149-156.
- Lewis, M., Alessandri, S.M. & Sullivan, M.W. (1990). Violation of expectancy, loss of control, and anger expression in young infants. Developmental Psychology, 63 , 630-638.
- Miller, J. F. & Leddy, M. (1999). Verbal fluency, speech intelligibility, and communicative effectiveness. In J.F Miller, M. Leddy & L.A. Leavitt (Eds.), Improving the Communication of People with Down Syndrome, (pp. 81-91). Baltimore, MD: Paul H. Brookes Publishing.
- Mon-Williams, M., Tresilian, J.R., Bell, V.E., Coppard, V.L., Jobling, A. & Carson, R.G. (2001). The preparation of reach to grasp movements in adults with Down syndrome. Human Movement Science, 20 , 587-602.
- Morss, J.R. (1983). Cognitive development in the Down's syndrome infant: Slow or different? British Journal of Educational Psychology, 53, 40-47.
- Mundy, P., Sigman, M., Kasari, C. & Yirmiya, N. (1988). Nonverbal communication skills in Down syndrome children. Child Development, 59 , 235-249.
- Mundy, P., Kasari, C., Sigman, M., & Ruskin, E. (1995). Nonverbal communication and early language acquisition in children with Down syndrome and normally developing children. Journal of Speech and Hearing Research, 38, 157-167.
- Ohr, P.S. & Fagen, J.W. (1991). Conditioning and long term-memory in three month old infants with Down syndrome. American Journal on Mental Retardation, 96 , 151-162.
- Ohr, P.S. & Fagen, J.W. (1994). Contingency learning in 9-month-old infants with Down syndrome. American Journal on Mental Retardation, 99 , 74-84.
- Piaget, J. (1952). The Origins of Intelligence in Children. New York: Norton.
- Pinter, J.D., Eliez, S., Schmitt, J.E., Capone, G.T. & Reiss, A.L. (2001). Neuroanatomy of Down's syndrome: A high-resolution MRI study. American Journal of Psychiatry, 158, 1659-1665.
- Pitcairn, T.K. & Wishart, J.G. (1994). Reactions of young children with Down's syndrome to an impossible task. British Journal of Developmental Psychology, 12 , 485-489.
- Pueschel, S.R., Gallagher, P.L., Zartler, A.S. & Pezzullo, J.C. (1987). Cognitive and learning profiles in children with Down syndrome. Research in Developmental Disabilities, 8 , 21-37.
- Rodgers, C. (1987). Maternal support for the Down's syndrome stereotype: The effect of direct experience of the condition. Journal of Mental Deficiency Research, 31 , 217-278.
- Rosner, B.A., Hodapp, R.M., Fidler, D.J., Sagun, J. & Dykens, E.M. (2004). Social competence in persons with Prader-Willi, Williams, and Down syndromes. Journal of Applied Research in Intellectual Disabilities, 17 , 209-217.
- Ruskin, E.M., Kasari, C., Mundy, P. & Sigman, M. (1994). Attention to people and toys during social and object mastery in children with Down syndrome. American Journal on Mental Retardation, 99 , 103-111.
- Sigman, M. & Ruskin, E. (1999). Continuity and change in the social competence of children with autism, Down syndrome, and developmental delays. Monographs of the Society for Research in Child Development, 64 , v-114.
- Uzgiris, I.C. & Hunt, J. M.V. (1975). Assessment in infancy: Ordinal scales of Psychological Development. Illinois: University of Illinois Press.
- Vaughn, B.E., Contreras, J. & Seifer, R. (1994). Short-term longitudinal study of maternal ratings of temperament in samples of children with Down syndrome and children who are developing normally. American Journal on Mental Retardation, 98 , 607-618.
- Vaughn, B.E., Goldberg, S., Atkinson, L., Marcovitch, S., MacGregor, D. & Seifer, R. (1994). Quality of toddler-mother attachment in children with Down syndrome: Limits to interpretation of strange situation behaviour. Child Development, 65 , 95-108.
- Vlachou, M., & Farrell, P. (2000). Object mastery motivation in pre-school children with and without disabilities. Educational Psychology, 20 , 167-176.
- Walden, T., Knieps, L. & Baxter, A. (1991). Contingent provision of social referential info by parents of children with and without developmental delays. American Journal on Mental Retardation, 96 , 177-187.
- Wang, P.P. & Bellugi, U. (1994). Evidence from two genetic syndromes for a dissociation between verbal and visuo-spatial short-term memory. Journal of Clinical and Experimental Neuropsychology, 16 , 317-322.
- Wetherby, A.M., Yonclas, D.G. & Bryan, A.A. (1989). Communicative profiles of preschool children with handicaps: Implications for early identification. Journal of Speech and Hearing Disorders, 54 , 148-158.
- Wishart, J.G. (1996). Avoidant learning styles and cognitive development in young children. In B. Stratford & P. Gunn, (Eds.). New Approaches to Down Syndrome, (pp.157-172). London: Cassell.
- Wishart, J.G. & Bower, T.G.R. (1984). Spatial relations and the object concept: a normative study. In L.P. Lipsitt & C.K. Rovee-Collier (Eds.). Advances in Infancy Research (vol 3) , (pp. 57-123). Norwood: Ablex.
- Wishart, J.G. & Duffy, L. (1990). Instability of performance on cognitive tests in infants and young children with Down's syndrome. British Journal of Educational Psychology, 60 , 10-22.
- Wishart, J.G., & Johnston, F. H. (1990). The effects of experience on attribution of a stereotyped personality to children with Down's syndrome. Journal of Mental Deficiency Research, 34 , 409-420.