Effect Size Differences: Schematic vs. Natural Prime

Graph 10: Accuracy for the main effect of action (exp. 3). The y-axis displays the percentage of correctly answered trials averaged across participants. The percentages are shown in the center of each bar.

6.4.4.3 Effect Size Differences: Schematic vs. Natural Prime

We also compared the effect sizes for the prime and action effects in the eye-tracking data between experiments 2 and 3. These two experiments mainly differed in terms of prime presentation. Whereas participants in experiment 2 were primed with a dynamic happy looking schematic smiley (see Figure 4), participants in experiment 3 were primed with a natural dynamic happy facial expression (see Figure 5). In order to directly compare the magnitude of the effect of the schematic prime with the magnitude of the effect of the natural prime, we ran repeated measure ANOVAs on the generalized eta squared effect sizes (of the F1 and F2 analyses) separately for the prime and for the action effects of the Verb, Adverb, Verb-Adverb, NP2 and Long region together (N=10), using prime presentation (natural vs. schematic) as the fixed factor.

We used Generalized eta squared (ŋG²) over other effect size measures (e.g., partial eta squared) because it is better suited for comparisons across studies and can also be used to compare effect sizes in within-study designs. It takes inter-study variations such as differing methods and analyses into account and is well suited for experiments with subtle effects. It has to be noted however, that ŋG² cannot be interpreted in the same way as partial eta squared, meaning that the magnitude of an effect cannot be determined by looking at the value of the effect size but always should be interpreted in relation to another effect size (cf., Bakeman, 2005; Lakens, 2013).

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94 90

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depicted action no action

percent accuracy

Main Effect of Action

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As Graph 11 shows, ŋG² for the action effect is higher in experiment 2 in which the schematic prime was used compared to experiment 3 which used the natural prime. This difference is significant (F(1,9)= 15.093, p< .05) and hence indicates that participants in the schematic prime experiment used the depicted action to a greater extent than participants in the natural prime experiment. This result becomes interesting when looking at Graph 12, which shows the difference in effect size for the prime effect.

Graph 11: Mean generalized eta squared of the action effect (of the Verb, Verb-Adverb, NP2 and Long region) for the natural face (exp. 3) compared to the schematic face (exp. 2) of the real-time data. The mean effect size is displayed on the y-axis. Error bars show the standard error.

Graph 12: Mean generalized eta squared of the prime effect (of the Verb, Verb-Adverb, NP2 and Long region) for the natural face (exp. 3) compared to the schematic face (exp. 2) of the real-time data. The mean effect size is displayed on the y-axis. Error bars show the standard error.

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natural schematic mean ŋG2

Action Effect

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natural schematic mean ŋG2

Prime Effect

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Graph 12 shows that the magnitude of the prime effect is significantly greater (F(1,9)= 5.636, p< .05) in experiment 3 (natural prime face) compared to experiment 2 (schematic prime face). Hence, participants made greater use of the natural compared to the schematic prime and at the same time reduced the use of the depicted action in experiment 3 arguably because they did not have to rely on the direct cue as much as in experiment 2 given the more accessible natural facial expression (vs. the schematic prime face).

However, effect sizes for the action effect were significantly higher than the effect sizes for the prime effect in both experiments 2 and 3 (independent two-tailed t-tests:

ps < .05). Given the strong and reliable main effects of action in the Verb, Adverb, Verb-Adverb, NP2 and the Long region in both studies and the present but marginal main effects of prime in experiment 3 this is not surprising. Nevertheless, regardless of effect size magnitude difference between the factors, the word region effect sizes for the individual regions for experiments 2 and 3 do not differ significantly from each other (independent two-tailed t-test: p= .346).

6.4.5 Summary and Conclusion

To conclude, experiment 3 replicated the strong effect of depicted action in younger adults. Crucially, when the prime was a dynamic natural facial expression, younger adults could also make use of this indirect visual social cue for OVS sentence processing and thematic roles assignment. However, although the effects of the natural positive emotional prime were present and significantly stronger than the effects of the schematic smiley, they were nonetheless less prominent than the effect of the depicted action. Moreover, the interaction means lead to the assumption that the visual social indirect cue is perhaps best used in combination with the direct cue.

Even though younger adults were able to use the indirect emotional cue for on-line thematic role assignment if the cue was natural, the effects that emerged were subtle. One reason for these weak effects might be the negativity bias that younger adults portray. The matching positive valence between the prime face and the target agent’s facial expression together with the positive valence of the adverb contributed to thematic role assignment; however, young adults overall have been shown to prefer negatively valenced emotional material. Hence, testing positive social cue integration using age groups that are more biased towards positive emotions might lead to

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stronger effects of indirect cue integration and thus further facilitate the processing of structurally challenging OVS sentences.

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