The author coded infants’ responses in each of the five test objects from the videotapes, A colleague who was taught to use the scoring system coded 30% of the data (3 children per condition) independently for the purpose of assessing inter-rater reliability. As in Experiment 1, reliability was obtained in three aspects: (1) the children’s first actions, or (2) first and second actions combined coded in each of the six scoring categories, or (3)
the target acts produced in the 20-second response period. Percentage agreement between the author and the colleague for infants’ responses falling into the pre-defined scoring categories as the first action was 92%, with a kappa of 0.86, similar to 90% and a kappa of 0.83 for their first and second actions combined. Percentage agreement for infants’ overall production of the target acts in the 20-second response period was quite high, 97% with a kappa of 0.93.
3.3. R esults
As in Experiment 1, the number of acts falling into each of the scoring categories was transformed into a proportion because three participants in the present study did not have a complete record of five response periods. One child in the Full-
Demonstration group walked away when the object set of box and stick was placed in front of her, apparently because she was scared of the beeping noise made by the experimenter. Two other missed data points were caused by a camcorder fault during the experiment: on one child’s response to the object set of loop and prong in the Emulation-Learning group and on one child’s response to that of beads and cylinder in the Full-Demonstration group. The means of the proportion of infants’ first acts and first and second acts combined coded in each of the scoring categories are presented in Table 3.2. As in Experiment 1, the four conditions were compared with regard to the proportion of infants' responses falling within the following categories, including Target Act (first act, and first and second acts combined, and in the 20- second response period). Failed Act (first act, and first and second acts combined). Spatial Contiguity (first act, and first and second acts combined), and Unfinished Target Act (first act, and first and second acts combined). These data were entered into one-way analyses of variance assessing the effect of condition. Following a one way ANOVA, pairwise comparisons were performed by the use of a Tukey HSD test. The subsidiary analyses included: (1) the latency to produce the target acts, (2) the proportion of infants’ first acts falling into the category of Other Act, (3) the parts of the objects that infants first touched, and (4) the number of infants using a finger to activate the beeper in the object set of box and stick.
3.3.1. M ain analyses
Target acts produced at first action
There was a significant difference in the proportion of target acts produced at the first action as a function of condition, F (3, 36) = 8.20, p< 0.001. Follow-up Tukey HSD tests showed that the infants produced significantly more target acts as their first acts in the Full -Demon strati on condition than they did in the Failed- Attempt, Spatial-Contiguity, and Emulation-Learning conditions, p < 0.003,
Table 3.2. Means of the proportion of 17-month-old children’s first actions and combination of first and second actions falling into each of the scoring
Condition Action Full- Demonstration Mean (SD) Failed- Attempt Mean (SD) Spatial- Closeness Mean (SD) Emulation- Learning Mean (SD) TA-1*‘ .62 (.27) .24 (.25) .28 (.22) .16 (.13) FA-1" .02 (.06) .06 (.10) .04 (.08) .04 (.08) SC-1" .04 (.08) .04 (.08) .08 (.14) .05 (.10) OA-1" .27 (.21) .60 (.25) .54 (.28) .70 (.19) NO-1" .00 (.00) .00 (.00) .00 (.00) .00 (.00) TA (UN)-l" .06 (.10) .06 (.10) .06 (.14) .02 (.06) TA(F)-1" .00 (.00) .00 (.00) .00 (.00) .04 (.08) Total 1.01 1.00 1.0 1.01 TA-1"-h2“‘^ .70 (.19) .38 (.29) .34 (.25) .34 (.25) FA-1"-f2“‘* .04 (.08) .10 (.14) .06 (.10) .08 (.14) SC-l"-h2““ .08 (.14) .06 (.10) .14 (.14) .05 (.10) 0A-1"-h2"‘’ .63 (.16) .80 (.25) .74 (.35) .80 (.16) N0-l"+2"‘^ .11 (.17) .04 (.08) .00 (.00) .16 (.25) TA (UN)-l" 2""^ .lO (.ll) .10 (.14) .08 (.17) .04 (.08) TA (F)-l"+2”‘* .00 (.00) .02 (.06) .04 (.08) .09 (.11) REPEAT .35 (.20) .50 (.22) .60 (.21) .46 (.26) Total 2.01 2.00 2.0 2.02 TA-20 sec .70 (.19) .44 (.32) .48 (.30) .39 (.22)
Note 1. TA-l" = target act produced at first action; FA-1*‘ = failed act produced at first action; SC-F‘ = spatial contiguity produced at first action; 0A-1*‘ = other acts produced at first action; NO-1" = no act produced at first action; TA (UN)-l" = unfinished target act produced at first action; TA (F)-l" = using finger to activate the beeper in the object set of box and stick at first action.
Note 2. TA-l"+2"‘* = target act produced at first and second actions combined; FA-l"-i-2"‘* = failed act produced at first and second actions combined; SC-l"+2”‘* = spatial contiguity produced at first and second actions combined; 0A-l"+2"‘‘ = other act produced at first and second actions combined; NO-
= no act produced at first and second actions combined; TA (UN)-l"+2”‘* = unfinished target act produced at first and second actions combined; TA (F)-1"-h2“‘^ = using finger to activate the beeper in the object set of box and stick at first and second actions combined; Repeat = repeated response. Note 3. TA-20 sec = target act produced within 20 seconds of the scoring period.
p < 0.009, and p < 0.001, respectively (see Figure 3.1). No group differences were found among the latter three conditions.
Target acts produced at first and second acts combined
There was a significant difference in the proportion of target acts produced at the first and second acts combined as a function of condition, F (3, 36) = 4.80, p< 0.007. Similar to the previous analysis, follow-up Tukey HSD tests revealed that the infants in the Full-Demonstration condition produced more target acts as the first and second acts combined than the infants in any of the Failed-Attempt, Spatial-
Contiguity, and Emulation-Learning conditions, p < 0.04, p < 0.02, and p < 0.02, respectively (see Figure 3.2). None of the latter three groups differed from one another significantly.
Target acts produced in 20-second response period
The effect of condition on the proportion of target acts produced in 20 seconds of the response period only reached a marginally significant level, F (3, 36) = 2.64, p = 0.069. Follow-up Tukey HSD tests showed that the infants in the Full-
Demonstration condition produced more target acts in the 20-second response period than the infants in the Emulation-Learning condition. However, the statistical
significance was marginal, p = 0.059 (see Figure 3.3). There were no other apparent group differences.
Failed acts
As can be seen in Table 3.2, the infants in the Failed-Attempt condition
reproduced few of the demonstrated failed attempts which had been observed: 6% as compared with 24% of the target acts produced as their first acts; and 10% as
compared with 38% of the target acts produced as their first and second acts combined. There was no significant difference in the proportion of demonstrated failed acts reproduced at either the first act or the first and second acts combined as a function of condition, F (3, 36) = 0.39, p > 0.7, and F (3, 36) = 0.48, p > 0.7,
I
u
Experimental condition
Note. FD = Full-Demonstration; FA = Failed-Attempt; SC = Spatial-Contiguity; EL = Emulation-Learning.
Figure 3.1. Means and 95% Cl of the proportion of 17-month-old children’s first actions coded in the category of Target Act (TA-1®*) as a function of condition.
u
Experimental condition
Note. FD = Full-Demonstration; FA = Failed-Attempt; SC = Spatial-Contiguity; EL = Emulation-Leaming.
Figure 3.2. Means and 95% Cl of the proportion of 17-month-old children’s first and second actions combined coded in the category of Target Act (TA-
1
Experimental condition
Note. FD = Full-Demonstration; FA = Failed-Attempt; SC = Spatial-Contiguity; EL = Emulation-Leaming.
Figure 3.3. Means and 95% Cl of the proportion of 17-month-old children’s actions produced during the 20-second response period coded in the category of Target Act (TA-20 sec) as a function of condition.
Spatial-Contiguity control acts
Similar to what they did in the Failed-Attempt condition, the infants in the Spatial-Contiguity condition reproduced relatively few of the acts actually demonstrated: 8% as compared with 28% of the target acts produced as their first acts; and 14% as compared with 34% of the target acts produced as their first and second acts combined. There was no significant difference in the proportion of spatial-contiguity control acts reproduced at either the first act or the first and second acts combined as a function of condition, F (3, 36) = 0.35, p > 0.7, and F (3, 36) = 1.24, p > 0.3, respectively.