Reference to the review in the introductory chapter will illustrate that several aspects of maternal speech to DS children have been found to be different from that directed towards "normal"
children. As discussed, these results are to some exctent
contentious, not the least because it is unknown vhether they are a positive and accurate adaptation to the child's own language level (that is, vhether they are child elicited), or vhether they are peculiar to the speech of mothers of DS childen, regardless of the actual behaviour exdiibited by the children (that is, whether they are mother elicited).
Thus the categories for analyses selected here were drawn from the findings in the literature on maternal speech to DS children.
elicited, then they would not be manifest in the experimental situation wherein a (supposed) DS child wcxild be exhibiting pxerfectly normal behaviour. Conversely, if any such differences are mother-elicited, then, it was hypothesised, they would manifest themselves even when confronted by "normal" behaviour, as shown by the DS-labelled child. However, it is also possible that an interaction between 2 such effects would occur; that is, that mothers would initially manifest certain such differences (for whatever reasons - be this through their experiences with their cwn DS child or through certain preconceptions they hold, or both) but that such behaviours only endure when maintained by the child's, own behaviour. Thus when confronted by "normal" behaviour, any effects should gradually decline. It was therefore decided to ccnpare not only mothers * behaviours to the DS-labelled twin versus the normal-labelled twin, but also, wnthin each of these categories, to ccnpare results over the first 3 minutes of interaction as against the second 7 minute pxeriod of interaction. This was done within the following categories;
(a) Amount of Vocalization
It has been noted by several researchers (e.g. Buckhalt et al, 1978; Buium et al, 1974; Petersen and Sherrod, 1982) that mothers of DS children talk more to their children than do mothers of
nonhandicapped mothers to theirs. The amount of productive
vocalisation shown by the mothers to the twins was thus measured by recording the amount of time each mother spent vocalising, and this was expressed as a percentage of either the early (3 minute) period or the later (7 minute) period.
Several studies have also found mothers of DS children to be more directive (e.g. Buium et al, 1974; Petersen and Sherrod, 1982; Wolf, 1975; Stoneman et al, 1983, etc.). Within this experiment, this was firstly investigated by observing the number of (i) positive ccnroands, and (ii) negative conmands/prohibitions used by subjects to the twins. These were counted within the early and late periods of the interaction sequences, and the number of ccnmands were expressed as a proportion of the total amount of vocalisation within each period (as measured in category (a), above).
(c) Offering Toys
Again with reference to the findings on maternal directiveness when in interaction with their DS child, and also with reference to studies indicating mothers' reluctance to allow handicapped children to initiate toy play (e.g. Brooks-Gunn and Lewis, 1982) the number of times each mother offered toys to the children, regardless of the child's response, was calculated as an index of the exctent to which they directed play sequences. The number of toy-offers was again counted in both early and late periods within each interaction sequence.
(d) Imitation
It has been observed (e.g. Petersen and Sherrod, 1982) that mothers of DS children seek more imitation from their preschooler children than do "normal" controls. Thus the nunber of times mothers sought imitation from the twins was counted, again within the early and later pxeriods of the interactions. Imitation is defined here as mothers requesting a child to repxeat a word/words.
Greater syntactic ccnplexity has also been noted in the speech of mothers to "normal" children than to DS children. In particular,
it has been observed (e.g. Buium et al, 1974) that mothers of DS children have a less ccqplex interrogative form than do "normal"
controls, in that they use fewer "Wh-" type questions. To
investigate this, mothers' use of (i) sinple interrogatives (i.e. those requiring only a yes/no answer as an appropriate response), and (ii) ccnplex interrogatives (i.e. "VJh-" questions requiring more ccnplex responses) were counted to both twins and within the early and late periods of each interaction, and this was then expressed as a proportion of the total amount of vocalisation for each period (as measured in category (a) above).
(f) Unresponsiveness
Literature on maternal communication to DS children also indicates that mothers are less responsive to their handicapped children’s initiations of interactions (e.g. Eheart, 1982; C.E. Cunningham et al, 1981) and also that they are involved in less semantically-related child dependent speech than their "normal" peers (Petersen and Sherrod, 1982). Thus, the nunber of times the twins either initiated, or attenpted to initiate a new conversation was noted, and the number of these that mothers ignored was likewise noted. These latter figures were then expressed as a proportion of the nunber of child initiations, or attenpted initiations within each period of the interaction sequences.
One 10-minute videotape was randomly selected of one of the mothers with one of the twin sisters. This was divided into 10 x 1 minute sections, using an electronic "bleeper". An independent observer analysed each one minute section, using the above behaviour categories, and inter-dbserver correlations were calculated between the independent observer's analysis and those of the Experimenter. Inter-dbserver reliability coefficients were found to range from r = 0.80 to r ~ 1.00, with a mean of 0,85. (These inter-observer reliability coefficients were not calculated for the categories of negative commands and imitation as these occurred so infrequently).
3.3.2 Results
Of the above categories, 2 proved to be inappropriate for analysis. . The first of these was category (bii) - negative coitmands. No subjects used any negative cctrmands or prohibitions whatsoever. The second of these 2 categories was category (d) - imitation. The amount of imitation sought was negligible, and thus did not lend itself to analysis. The data from the remaining 6 categories is presented in Tables 3.1 and 3.2 and in the Appendix, Tables A.3 and A.4 (see also Fig. 3.1, Graphs a-f). These remaining 6 categories were analysed using a repeated measures analysis of variance (labels x categories x periods). As categories of positive commands, siitple interrogatives and conplex interrogatives are all expressed as proportions of the total amounts of vocalisation, they are not independent of this latter category and were thus examined in one ANOVA, with the remaining categories of vocalisaticxi, offering toys and responsiveness, being analysed in another ANDVA.
This ANOVA (see Table 3.1) found firstly a statistically
significant nrnin effect for Categories. However, as the 3
categories here are independent and measured in different units, such a result is meaningless on all but a statistical level. Of more interest, the labels x categories interaction was found to be highly significant (F = 8,8852, with 20 d.f., 0.001 < p < 0.002). No other significant main effects or interactions were found in this ANOVA.
Post hoc analyses were then conducted to more fully examine the labels x categories interaction (See Fig 3.1); Tukey's
HSD test yielded a value of q of 7.90 at the 5% level and 10.73 at the 1% level. Multiple conparisons between the 2 labels, for each category thus reveal that the labelling factor only has an effect at the level of the Unresponsiveness category (p < 0.01); there was no effect for the Vocalisation or Offering Toys categories.
However, whilst the use of analyses of variance reduces the chance of making a Type 1 error, as associated with the multiple use of single corparison tests, such as repeated t-tests, given that this specific ANOVA embodied categories of very different scales, it was hypothesised that a Type 2 error could have occurred due to the very low numbers of the Offering Toys category spuriously affecting the mean square error term and thus producing an inappropriately
conservative test. T-tests for correlated sanples were thus
conducted on the data for the 3 categories vhen it was confirmed that an insignificant difference did indeed exist-between mothers' offering of toys to the 2 chldren (t = 0.93 with 10 d.f., p > 0.05) but amounts of maternal vocalisation were found to be significantly
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