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Purpose The purpose of this study was to determine whether children who stutter (CWS) and typically developing children (TDC) differ from each other on composite temperament factors or on individual temperament scales. Methods Participants consisted of 116 age and gender-matched CWS and TDC (3.04–8.11). Temperament was assessed with a Dutch version of the Children's Behavior Questionnaire (CBQ-D; Van den Bergh and Ackx, 2003), a caregiver rating scale. Results Results indicated significant differences between participant groups on the composite temperament factors of Negative Affectivity, and Effortful Control. Analysis of the individual temperament scales showed that CWS, compared to the TDC, scored significantly lower on the scales of ‘Inhibitory Control’ and ‘Attentional Shifting’ and higher on the scales of ‘Anger/Frustration’, ‘Approach’ and ‘Motor Activation’. Stuttering severity and months of therapy were not associated with either of the temperament dimensions. Conclusions The present study provides data that support the hypothesis that CWS and TDC differ on both composite temperament factors and temperament scales. The findings were interpreted within existing frameworks of temperament development, as well as with regard to previous studies of temperament in CWS. Educational objectives: After reading this article, the reader will be able to: (1) describe the concept of temperament, including Rothbart's temperamental model, and its functional significance; (2) explain the CBQ-based (Children's Behavior Questionnaire) temperamental differences between CWS and CWNS; and (3) explain possible pathways for interaction between temperament and the development of stuttering.

The purpose of this study was to investigate the relationship between temperament and developmental stuttering, using the Children's Behavior Questionnaire—Dutch (CBQ-D; Van den Bergh & Ackx, 2003), a parental temperament questionnaire. Because temperament has been defined and interpreted differently in the last decades, we start the introduction by addressing the concept of temperament. This is followed by a brief review of the role of temperament in the development of behavioral disorders, followed by a review of current research on temperament and developmental stuttering. 1.1. The concept of temperament At present, most theorists agree that temperament refers to biologically based individual differences that are relatively stable over time, and appear early in the child's development (e.g., Goldsmith et al., 1987). Early approaches stressed the importance of stability of these traits (Buss and Plomin, 1984 and Costa and McCrae, 2001) and saw it as a behavioral (Thomas & Chess, 1977) or primarily emotion-oriented style (Goldsmith & Campos, 1982). More recent models acknowledge that temperament itself develops over time (Goldsmith, 1996, Plomin and Dunn, 1986 and Rothbart, 1989), incorporates motivational and self-regulatory systems (Posner & Rothbart, 1998) and is influenced by environmental interactions (Arcus, 2001, Halverson and Deal, 2001 and Saudino, 2005). Rothbart defines temperament as ‘constitutionally based individual differences in reactivity and self-regulation’ (Rothbart, Ahadi, Hershey, & Fisher, 2001). In her definition, ‘reactivity’ refers to the arousability of physiological and sensory response systems, and ‘self-regulation’ are those processes that can modulate (facilitate or inhibit) one's reactivity. ‘Constitutional’, in turn, is referring to the individual's biological basis, influenced over time by genetics, maturation, and experience. In other words, the temperament structure changes over time, from a predominantly reactivity-driven concept in infants to a structure with more emphasis on self-regulatory processes in older children (Putnam, Ellis, & Rothbart, 2001). In order to assess temperamental characteristics, Rothbart developed a number of questionnaires aimed at different age ranges. The Children's Behavior Questionnaire (CBQ; Rothbart et al., 2001) assesses temperament in early to middle childhood and consists of 15 temperament scales. Factor-analyses of these scales repeatedly have revealed 3 composite temperament factors, namely positive reactivity (i.e., the tendency to actively and energetically approach new experiences in an emotionally positive way), negative reactivity (i.e., the tendency to be sad, fearful, easily frustrated, and irritable), and effortful control (i.e., the ability to sustain attention, control one's behavior, and regulate one's emotions) (Ahadi et al., 1993, Eggers et al., 2009, Kusanagi, 1993, Rothbart et al., 2001 and Van den Bergh and Ackx, 2003). In the CBQ, Positive Reactivity (or Extraversion/Surgency) comprises the scales Impulsivity, Activity Level, High Intensity Pleasure, Motor Activation, Shyness, Approach, and Smiling/Laughter. Negative Reactivity (or Negative Affectivity) comprises the scales Anger/Frustration, Discomfort, Sadness, Fear, and Falling Reactivity/Soothability. Low Intensity Pleasure, Inhibitory Control, Perceptual Sensitivity, Attentional Focusing, Attentional Shifting, and Excitatory Control cluster under Effortful Control (Van den Bergh & Ackx, 2003; for scale definitions and questionnaire sample items see Table 1). Table 1. Scale definitions of the Children's Behavior Questionnaire-Dutch (CBQ-D) and sample items (Van den Bergh & Ackx, 2003). Scale Definition Extraversion/surgency 1. Impulsivity The speed of response initiation. Sample item: Usually rushes into an activity without thinking about it. 2. Activity level The level of gross motor activity including rate and extent of locomotion. Sample item: Moves about actively (runs, climbs, jumps) when playing in the house. 3. High intensity pleasure The amount of pleasure or enjoyment related to situations involving high stimulus intensity, rate, complexity, novelty, and incongruity. Sample item: Likes to play so wild and recklessly that s/he might get hurt. 4. Motor activation The amount of excess repetitive small-motor movement, such as finger tapping. Sample item: Fidgets during quiet activities, such as hearing a story, looking at pictures. 5. Shyness Slow or inhibited approach in situations involving novelty or uncertainty. Sample item: Sometimes prefers to watch rather than join other children playing. 6. Approach The amount of excitement and positive anticipation for expected pleasurable activities. Sample item: Becomes very excited while planning for trips. 7. Smiling/laughter The amount of positive affect in response to changes in stimulus intensity, rate, complexity, and incongruity. Sample item: Laughs a lot at jokes and silly happenings. Negative affect 8. Anger/frustration The amount of negative affect related to interruption of ongoing tasks or goal blocking. Sample item: Gets quite frustrated when prevented from doing something s/he wants to do. 9. Discomfort The amount of negative affect related to sensory qualities of stimulation, including intensity, rate or complexity of light, movement, sound or texture. Sample item: Is quite upset by a little cut or bruise. 10. Sadness The amount of negative affect and lowered mood and energy related to exposure to suffering, disappointment, and object loss. Sample item: Becomes upset when loved relatives or friends are getting ready to leave following a visit. 11. Fear The amount of negative affect, including unease, worry or nervousness related to anticipated pain or distress, and/or potentially threatening situations. Sample item: Is afraid of loud noises. 12. Falling reactivity/soothability The rate of recovery from peak distress, excitement or general arousal. Sample item: Calms down quickly following an exciting event. Effortful control 13. Low intensity pleasure The amount of pleasure or enjoyment related to situations involving low stimulus intensity, rate, complexity, novelty, and incongruity. Sample item: Enjoys “snuggling up” next to a parent. 14. Inhibitory control The capacity to plan and to suppress inappropriate approach responses under instructions or in novel or uncertain situations. Sample item: Can easily stop an activity when s/he is told “no”. 15. Perceptual sensitivity The amount of detection of slight, low intensity stimuli from the external environment. Sample item: Is quickly aware of some new items in the living room. 16. Attentional focusing The tendency to maintain attentional focus upon task-related channels. Sample item: When picking up toys or other jobs, usually keeps at the task until it's done. 17. Attentional shifting The ability to transfer attentional focus from one activity/task to another. Sample item: Can easily shift from one activity to another. 18. Excitatory control The capacity to perform an action when there is a strong tendency to avoid it. Sample item: Forces her/himself to complete projects, even when tired. Table options 1.2. Temperament as a moderator in the development of behavioral disorders Child temperament researchers recognize how both innate individual differences and the environmental context shape children's behavior. In particular, temperamental concepts are being used to explain behavioral and physiological patterns, and responses that are evoked under conditions of stress (e.g., novelty situations, interaction with unfamiliar persons, intense stimuli), and conditioned responses to certain stimuli (Gray, 1987 and Strelau, 2001). Moreover, the idea of temperament predisposing the susceptibility for or moderating the development of certain disorders (e.g., anxiety disorders) has received widespread attention in health psychology literature (e.g., Kubzansky et al., 2009, Puttonen et al., 2008, Smith and Williams, 1992 and Williams et al., 1992). Recent integration of temperamental research and childhood psychopathology (Frick, 2004, Nigg and Goldsmith, 1998 and Rettew and McKee, 2005) has created new insights in possible ways of temperament interaction. For instance, there is mounting empirical evidence that both reactive temperamental factors (Extraversion/Surgency and Negative Affectivity) as well as regulative processes (Effortful Control) play an important role in the onset, development and maintenance of disorders such as anxiety disorders (Bijttebier and Roeyers, 2009 and Lonigan and Vasey, 2009). Temperament dimensions have also been identified as important individual characteristics influencing the child's reaction to specific types of treatment (Mash, 2006) and moderating or mediating treatment outcome in various disorders such as anxiety disorders (Rapee & Jacobs, 2002) and attention deficit and hyperactivity disorder (Purper-Ouakil et al., 2010). 1.3. Temperament and developmental stuttering Recently, several researchers have considered the potential role of temperament in the onset and development of stuttering. For instance, Conture et al. (2006) have proposed the ‘Communication-Emotional model of stuttering’. In this model, distal (i.e., genetics and environment) and proximal contributors (i.e., speech-language planning and production) are linked with exacerbating factors (i.e., experience, emotional reactivity and regulation) and overt stuttering behaviors. They hypothesized that children begin to stutter as a result of deficiencies in speech-language planning and production. The presence of emotional reactivity may lead some children, after continued experience with stuttering, to react stronger to these disfluencies. Trying to cope with these disfluencies (regulation) may interact directly with linguistic planning and execution. Furthermore, Conture et al. suggested that this emotional reactivity/regulation consequently may lead to changes in disfluency types, duration, and/or physical tension. However some recent findings do not seem to support this extension of their model (Mulcahy, Hennessey, Beilby, & Byrnes, 2008). Other authors have speculated about the possible significance of temperament and/or temperament-related concepts (such as sensitivity towards stuttering, perfectionism, frustration tolerance, anxiety) for understanding the onset, development, and even treatment efficacy of stuttering (Anderson et al., 2003, Amster, 1995, Conture, 1991, Conture, 2001, Conture and Melnick, 1999, Embrechts et al., 2000, Felsenfeld et al., 2000, Gregory, 2003, Guitar, 1976, Guitar, 1998, Guitar, 2003, Karrass et al., 2006, Lewis and Goldberg, 1997 and Messenger et al., 2004; Oyler (1998) in Zebrowski and Conture, 1998 and Wakaba, 1998). Guitar (1998) for example speculates that some CWS might be born with a heightened emotional sensitivity (hypersensitivity) making them “especially reactive to their early disfluencies” (pp. 83). Temperament also may be a useful concept to understand the influence of stress and specific stressors on stuttering. It has been demonstrated that stuttering can be influenced by emotional reactions as a result of situational stress (e.g., Alm, 2004a, Blood et al., 1994, Ezrati-Vinacour and Levin, 2004, Menzies et al., 1999 and Peters and Hulstijn, 1984). Temperament differences may affect the susceptibility of individuals to learning processes and experiences. For instance, specific temperament traits, such as extraversion, make some individuals more susceptible to particular classical and operant conditioning processes (Gray, 1991), which are known to have an important role in the development of compensatory and other behaviors in stuttering (Bloodstein, 1995, Brutten and Shoemaker, 1967 and Kamhi, 2003). Previous studies, employing parental temperament questionnaires, have reported temperament differences between CWS and typically developing children (TDC) (Anderson et al., 2003, Embrechts et al., 2000, Karrass et al., 2006 and Lewis and Goldberg, 1997; Oyler (1998) in Zebrowski and Conture, 1998 and Wakaba, 1998) and provided support for the interactional patterns of temperament and stuttering described above. The results of these studies, in general, showed that CWS scored significantly lower on scales related to self-regulation (e.g., inhibitory control, adaptability), and higher on reactivity related scales (e.g., activity, impulsivity) compared to children in the control group (for a more detailed overview: see Eggers et al., 2009). In the present study, the Children's Behavior Questionnaire (CBQ; Rothbart et al., 2001) was used to study temperament dimensions of stuttering and nonstuttering children. Several approaches can be used for assessing temperament, including behavioral observations in natural (home) or in more structured semi-natural (laboratory) settings (e.g., Goldsmith & Rothbart, 1991), interviews (e.g., Garrison et al., 1990 and Thomas and Chess, 1977), temperament questionnaires (e.g., Carey and McDevitt, 1978, Duijsens et al., 1999 and Gartstein and Rothbart, 2003), or psychophysical and psychophysiological indicators (Kagan, 1998 and McManis et al., 2002), as well as a combination of two or more of these methods. Although temperament questionnaires can be susceptible to parental bias and inaccuracy (Vaughn, Taraldson, Cuchton, & Egeland, 2002), they tap into the vast knowledge of caregivers who have experienced the child's reactions in different situations and over a long period of time. Also, several studies have shown satisfactory test-retest reliability (Slabach, Morrow, & Wachs, 1991), as well as a moderate to strong degree of validity for parental reports (Rothbart & Bates, 1998). Our choice for using the CBQ was based on three elements: (a) the theoretical basis of the questionnaire (e.g., multidimensionality), (b) the availability of a reliable and valid Dutch translation (Van den Bergh & Ackx, 2003), and (c) the age range for usability of the CBQ. Moreover, one of the greatest advantages of this theory-derived instrument, compared to other questionnaires, is that it includes scales that measure traits developing past infancy, resulting in a more varied and detailed view on temperament at that age. In addition, the CBQ not only focuses on behavioral style characteristics but also includes affective qualities, such as strength and speed of responses to emotional stimulation. Prior to the current study, we investigated whether the structure of the underlying construct being measured was identical for both participant groups. Although there were some minor scale loading differences, the factor-analyses of the CBQ-data obtained from CWS, TDC, and children with vocal nodules in this preceding study (Eggers et al., 2009), revealed, a similar and highly congruent three-factor temperament structure. Given this similarity in temperament structure between the participant groups we can conclude that if group differences between CWS and TDC on the composite temperament factors (e.g., Effortful Control) or individual temperament scales (e.g., Inhibitory Control) would emerge, they reflect real differences and are not confounded by differences in underlying temperamental make-up between the two groups (Byrne, Shavelson, & Marsh, 1993). Based on our overview of the literature, we know that high levels of negative reactivity and low levels of effortful control have an impact on disorder onset (e.g., Bijttebier & Roeyers, 2009), and that temperament plays a role in stress responses, conditioning processes (e.g., Gray, 1987), and treatment outcome (e.g., Purper-Ouakil et al., 2010). With regard to stuttering, studies in CWS have revealed elevated scores on reactivity-related scales and lowered scores on self-regulatory scales (for an overview: see Eggers et al., 2009). However, while many of the findings from these previous studies in stuttering can be understood as pointing towards increased reactivity or reduced self-regulation, with the exception of a study by Embrechts et al. (2000), who used a preliminary version of the CBQ, no studies employed a questionnaire specifically conceptualized to measure the triad of positive/negative reactivity and self-regulation in a highly integrated manner. Moreover, previous researchers did not validate their results by evaluating if the structure of the underlying construct being measured was similar for all groups. Therefore, the current study builds on the results reported in our previous paper in which we showed the underlying temperamental construct was similar for both speaker groups. Specifically, in this study, we used the CBQ, a questionnaire that includes the three composite temperament factors, to investigate the following research questions: (a) do CWS, compared to TDC, have a heightened score on the composite temperament factors of Negative Affectivity and/or Extraversion/Surgency and on some of the individual reactivity-related scales; (b) do CWS, compared to TDC, have a lower score on the composite temperament factor of Effortful Control and on some of the individual scales related to self-regulation; (c) is temperament in CWS associated with length of therapy and/or stuttering severity.

The present study provides further data supporting the hypothesis that CWS and typically developing children differ in temperamental characteristics. Evidence was found for heightened reactivity (higher in Negative Affect, and in individual scales of Anger/Frustration, Motor Activation, and Approach) and limited processes of self-control (lower in Effortful Control, and in individual scales of Inhibitory Control and Attentional Shifting). While communication disorders may worsen or improve over time, temperament is supposed to be relatively stable (Rothbart, Derryberry, & Hershey, 2000). So the study of temperament may offer a way to capture pre-onset causal, trigger or contributing factors as opposed to reactive effects of the communication disorder. Trying to formulate clinical considerations is quite premature since further research, based on direct observations, behavioral experiments, psychophysical, and/or psycho physiological measures is still needed for a multidimensional and more detailed view of possible differences and relationships. However, such research may provide additional information that would allow clinicians to match treatment approach with specific temperamental patterns observed in individual CWS. It also may shed further light on issue of spontaneous recovery and treatment outcome. If the current results are confirmed in follow-up studies, they could validate the frequently described use of desensitization training for the moments of stuttering but also for specific stress inducing stimuli or environments (e.g., Gregory, 2003, Shapiro, 1999 and Van Riper, 1973) as this will reduce the reactivity of a child towards certain stimuli. It would also illustrate the importance of parental guidance (e.g., Rustin et al., 1996 and Shapiro, 1999) in young CWS, training parents to react adequately to certain behaviors and situations. Children with heightened Negative Reactivity may benefit from a less protective parenting style, allowing them to acquire essential coping strategies, while children with lowered Effortful Control may experience more difficulties with an authoritarian or permissive parenting style (Kristal, 2005 and Kochanska, 1993).