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  • The findings are also consistent with the few prior studies

    2018-10-25

    The findings are also consistent with the few prior studies that have indexed social perception using the P400 component. The same ERP component that here indexes social valence has previously been documented to index social perception of various stimuli, including goal directed grasping (Bakker et al., in press), pointing (Gredebäck et al., 2010; Melinder et al., in press) and gaze direction (Senju et al., 2006). In those studies functional and goal directed actions resulted in larger amplitudes than non-goal directed and/or non-functional events. We suggest that the current results fit in with this interpretation under the assumption that 6-month-olds are more readily attuned to process positive compared to negative valenced social actions. This processes is indexed by ERP component P400. This assumption receives support from the observation that across a variety of social modalities, infants in their first 6 months devote more attention to positive stimuli, with a hsp90 inhibitor bias toward negativity developing later (Vaish et al., 2008). Furthermore, specifically in the hill climber paradigm young infants devote more visual attention to the helper than the hinderer (Hamlin et al., 2010). However, this latter study also demonstrates that 3-month-olds discriminate a hinderer from a neutral actor but not a helper from a neutral actor. Together, these findings are not yet fully interpretable. What is clear however is that the infant P400 response is general to a broad range of social stimuli including not only the discrimination of more or less functional actions but also the discrimination of valenced social actions. The P400 component not only indexes social perceptual processes that relate one person\'s actions to immediate goals (Bakker et al., in press; Gredebäck et al., 2010; Senju et al., 2006) but also to interactions between social agents. Though the current stimuli belong to a somewhat different class of social events it hsp90 inhibitor is possible that current P400 response maps the same underlying neural networks dedicated to other forms of social perception. One design difference between microfilaments study and previous studies of the infant P400 reveals a new aspect of the P400. In previous studies, condition differences were directly perceivable in the test stimuli, for example because a pointing gesture was congruent or incongruent with an object location displayed a fraction of a second previously. In this study, however, there were no differences in the directly perceivable properties of the test stimuli (the agents themselves). Rather, agents differed in behavior displayed during the training stimuli, which were presented separately. Most infants saw a full set of 40 test trials, which lasted 68s, meaning test trials were presented on average 34s after a training stimulus. Different responses to different agents based on their previous history of social interaction imply that infants encode in memory attributions of valence to specific agents (Hamlin et al., 2013a). The current results indicate that the infant P400 can index not only immediate evaluations of social stimuli but also activation of memory of properties associated with particular agents. It is difficult to connect ERP components to specific spatial locations on the cortex, in the absence of source localization. However, with respect to P400, there is a strong candidate area that has previously been associated with this neural marker. Nelson et al. (2006) argue that the infant P400 is functionally similar to the adult N170 component (see also Csibra et al., 2008; de Haan et al., 2003; Nelson et al., 2006). In turn, the adult N170 component has been connected with the STS using both source localization of ERP data (Itier and Taylor, 2004) and joint recordings of ERP and fMRI (Dalrymple et al., 2011). One possibility, that requires further study before firm conclusions can be made, is that the P400 component demonstrated for pro- and antisocial agents in 6-month-olds originates from processes similar to those underlying other forms of social perception, namely STS activity (Gredebäck et al., 2010).