Time Course Differences

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Chambers (2013) found contrasting evidence supporting a negativity bias, at least for vocal affect. Additionally, Vaish et al. (2008) argue for a hard-wired negativity bias based on ontogenetic mechanisms that is present from early infancy. However, recall that this contrasts with neuroimaging studies demonstrating a higher amygdala activation for positive (versus negative) emotional faces for both children and older adults but a higher activation for negative (versus positive) emotional faces for younger adults (Mather et al., 2004; Todd et al., 2012; Todd et al., 2010), hence demonstrating a positivity bias for children and older adults but a negativity bias for younger adults. This bell-shaped development in emotional preferences directly contrasts with arguments for a hard-wired negativity bias.

Thus, whereas there is considerable evidence supporting the positivity bias in older age, there are at least some contrasting findings regarding the positivity bias in young children. Our findings that 4-5-year old children are not yet able to benefit from positive emotional faces for thematic role assignment and the processing of positively valenced OVS sentences might thus additionally be due to a weaker influence of positive emotional facial expressions on children compared to the influence on older adults.

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effects as our studies showed, i.e., a delay in the depicted action effect for children compared to younger adults when an action was (vs. was not) depicted.

Children’s eye-movements to a visual display can be mediated by the linguistic input with a very similar time course, as is the case for adults in canonical SVO sentences. Thus we do not believe that a different time course with which children link visual to linguistic input is the reason for children’s delayed visual context effects (see e.g., Mani & Huettig, 2012; Nation et al., 2003). Moreover, in a Visual-World-Paradigm study measuring children’s and adults’ eye-movements, Borovsky, Elman and Fernald (2012) suggested that children are just as quick as adults when it comes to real-time sentence comprehension of canonical sentences and the anticipation of an expected target object depicted in a visual display and mentioned in the sentence.

However, even though anticipation speed did not vary between children and adults, when controlling for age-specific vocabulary size, participants with higher vocabulary size looked earlier at the target than participants with lower vocabularies (Borovsky et al., 2012, see also Mani & Huettig, 2012). Hence, as we did not test children’s and younger adults’ vocabularies, we cannot exclude that children’s delay in target agent anticipation might be driven by the majority of them having relatively low vocabulary scores.

Another reason for the delayed action effect in children might however be the OVS sentences. As discussed in Section 2.3 4-5-year old children cannot yet make use of case marking as a cue to assign thematic roles in OVS sentences. Thus they initially interpret an OVS sentence as a canonical SVO sentence. The later use of the depicted action to assign thematic roles compared to younger adults might be due to some kind of repair effect. Children looked at the scene depicting three characters and heard what they believed was an SVO sentence starting with the subject as the agent.

They interpreted the first mentioned character as the agent (and not the patient) and might hence have expected him to perform an action. Once they heard the verb denoting the action they expected the first mentioned character, i.e., the agent in their interpretation, to be the performer of this action. However, in contrast to seeing their expected agent performing the mentioned action (which he did not do because he was in fact the patient), they searched for the action denoted by the verb and found it

“attached” to another not yet mentioned character, i.e., the real agent of the action in the OVS sentence. They hence revised their initial SVO interpretation on the basis of

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this visual cue and anticipated the target agent, thus interpreting the acting character as the true agent. Yet, this repair based on the depicted action took time and the anticipation happened later than it did for the younger adults.

Younger adults in contrast did not need a repair mechanism because they knew already when encountering the first determiner of NP1 that it was an OVS sentence.

They expected the agent to be mentioned in NP2 of the sentence and could very quickly use the depicted action to anticipate the target agent without an additional repair step.

Yet, older adults showed the same time course effects as children since they were one word region delayed for the integration of the depicted action into sentence processing. Likely, older adults have, like younger adults, no problems in comprehending OVS sentences and using case marking. Hence, they were unlikely to be delayed in visual cue use because they needed to use a repair mechanism. Still older adults seem to predict, i.e., generate expectancies about, upcoming linguistic input less well than younger adults (DeLong, Groppe, Urbach, & Kutas, 2012;

Federmeier, McLennan, Ochoa, & Kutas, 2002). However, Federmeier et al. (2002) and DeLong et al. (2012) measured linguistic prediction skills of older and younger adults using ERPs. Participants had to read (DeLong et al., 2012) or listen to (Federmeier et al., 2002) sentences ending in a more or less expected word. ERP responses (in terms of different N400 effects) showed that younger but not older adults could use the already processed linguistic input to predict what will come next in the sentence. However, our studies provided extra-linguistic visually depicted cues that facilitated language comprehension in real-time. Hence, it might be the case that older adults’ prediction / expectancy generation skills are overall worse than younger adults’, but as our results suggest they can still anticipate / generate expectancies about upcoming context given a supportive visual context. Still, they were delayed by one word region compared to younger adults.

This delay extended to the use of the indirect visual cue, i.e., the positive emotional prime face. Older adults only seemed to be able to use the indirect cue once the target agent had already been named and not to anticipate the correct role filler during the adverb region, as it was the case for the younger adults. Older adults could however integrate emotionaly valenced faces into emotionally valenced sentences in

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real-time and with the same time course as younger adults (Carminati & Knoeferle, 2013).

Yet there might be two alternative explanations for this delayed effect of the indirect emotional cue. First of all, given that older adults cannot predict upcoming input as quickly / in the same way as younger adults and given that the emotional valence of the positive prime face was mediated by the adverb, older adults might not have had a chance to use the indirect cue to anticipate the correct role filler since the target agent was mentioned directly after the adverb. Hence, we might have seen an anticipatory use of the emotional prime face if the sentence structure was different, such that the mediating emotionally valenced word was not directly followed by the to be anticipated target agent, i.e., the subject of the sentence.

Alternatively, older adults’ late use of the positive emotional prime face for real-time sentence processing might be related to the underlying mechanisms of their positivity bias. As discussed in Section 3.7.1.2, older adults’ fixation towards positive emotional faces (vs. negative faces) only started 500 ms after stimulus onset and moreover increased over time (Isaacowitz et al., 2009). Isaacowitz et al. (2009) see the reason for this in older adults cognitive control, i.e., the shift towards positive material is costly in cognitive resources and takes times. It could hence be the case that older adults could not use the positive emotional prime face for thematic role assignment as quickly as younger adults because they did not “simply” link their interpretation of the positive prime face to the positive valence of the adjective and the positive facial expression of the target character due to a congruency in positive emotional valence. Rather because their positivity bias is based on a top-down, cognitive control process (assuming this is the case, but see the discussion in Section 3.7.1.2), older adults needed more time to use the positive emotional facial expression in real-time sentence processing compared to younger adults.