RESUMO
Many developmental studies have examined the effects of joint attention. However, it has been difficult to compare effects of initiating joint attention and responding to joint attention in infants. Here, we compared the effects of initiating joint attention and responding joint attention on object information processing, object preference, and facial preferences in infants. Thirty-seven infants (10 to 12 months of age) were shown stimuli in which a female gazed towards or away from an object. Participants were assigned to initiating joint attention condition or responding joint attention condition. Results suggest that initiating joint attention promoted object information processing, whereas responding joint attention did not. Both joint attention conditions affected the facial preference for the person who engaged joint attention. In addition, after initiating joint attention, infants chose objects gazed by other person more often than after responding joint attention. It appears that attentional behaviours that precede the perception of certain stimuli affect infants' cognitive responses to those stimuli.
Assuntos
Atenção , Cognição , Percepção Visual , Expressão Facial , Feminino , Humanos , Lactente , MasculinoRESUMO
The present study used functional near-infrared spectroscopy (fNIRS) to measure 5- to 6-month-old infants' hemodynamic response in the prefrontal cortex (PFC) to visual stimuli differing in saliency and social value. Nineteen Japanese 5- to 6-month-old infants watched video clips of Peek-a-Boo (social signal) performed by an anime character (AC) or a human, and hand movements without social signal performed by an AC. The PFC activity of infants was measured by 22-channel fNIRS, while behaviors including looking time were recorded simultaneously. NIRS data showed that infants' hemodynamic responses in the PFC generally decreased due to these stimuli, and the decrease was most prominent in the frontopolar (FP), covering medial PFC (MPFC), when infants were viewing Peek-a-Boo performed by an AC. Moreover, the decrease was more pronounced in the dorsolateral PFC (DLPFC) when infants were viewing Peek-a-Boo performed by an AC than by a human. Accordingly, behavioral data revealed significantly longer looking times when Peek-a-Boo was performed by an AC than by a human. No significant difference between Peek-a-Boo and non-Peek-a-Boo conditions was observed in either measure. These findings indicate that infants at this age may prefer stimuli with more salient features, which may be more effective in attracting their attentions. In conjunction with our previous findings on responses to self-name calling in infants of similar age, we hypothesize that the dynamic function of the MPFC and its vicinity (as part of default mode network (DMN): enhanced by self-focused stimuli, attenuated by externally focused stimuli), which is consistently observed in adults, may have already emerged in 5- to 6-month-old infants.