افزودن بو: پریشانی‌ کمتر و توجه پیشرفته برای کودکان 6 ماهه

The effect of odor on cognitive and emotional processes has been studied in adults and children, but less so in infants. In this study twenty-seven six-month-olds were presented with a video while in either an odor (pine or baby-powder) or a no odor control condition. The video was a 92-s audiovisual presentation of a woman expressing happiness and sadness, with the order of emotion counterbalanced. Infant attention (looking time) and emotional expression (smiling, crying, mouthing) were coded. Infants looked longer in the presence of odor and expressed less crying and mouthing but more smiling behavior. Presence of odor markedly reduced infant emotional distress and increased attention, suggesting that the olfactory sensory system provides cues to infants that support mood regulation and maintain attention. These results have implications for optimizing infant environments for emotional health and cognitive development.

There is an old rhyme – “little drops of water, little grains of sand, make the mighty ocean and the pleasant land” (Carney, 1845). Analogously, “little” features of an infant's surround might “make” a more pleasant “land” or environment for an infant and thereby influence perceptual and cognitive development, possibly producing “mighty” or at least noticeable systemic benefits. Physical health, as well as important cognitive processes in adults and children, has been shown to be supported by sensory surrounds that enhance positive emotion (Ashby et al., 1999, Danner et al., 2001 and Fredrickson and Levenson, 1998). We predict that similar effects also occur during infancy, when longer term cumulative effects are probable. Even a simple process such as “looking” or attention span may be affected by positive visual, auditory and, in the present case, olfactory information in the surround. 1.1. The importance of olfaction This study focuses on olfaction for several reasons. First, it is the only sensory system directly connected to the ventral tegmental area (VTA), a dopamine producing area of the brain (Ashby et al., 1999), which is thought to be linked to mood regulation. Additionally, the importance of the olfactory system is suggested by evidence that more of the human genome is devoted to olfaction than other sensory systems (Buck & Axel, 1991) as well as by the early development of the olfactory system (Schaal, Marlier, & Soussignan, 2000). Olfaction therefore has more potential to influence early affective connections and cognitive sequelae than other sensory systems. Researchers have focused less on olfaction, however, and have attended less to its potential in cognitive developmental processes. 1.2. Emotion regulation By six months of age infants can regulate their distress, and the manner in which they do so in response to audio–visual information from the environment is well understood. Six-month-olds readily discriminate negative from positive emotional expressions and can respond with emotional displays indicating distress (Walker-Andrews, 1997). When the emotional expression of sadness is on their mothers’ face, infants demonstrate this ability even earlier, showing sadness and self-soothing when their mothers are sad (Tronick & Gianino, 1986). Although infants look away to the side or down when their mothers are angry or sad, they will continue to attend to a happy mother even when her expression is not contingent upon the infant reaction (Haviland & Lelwica, 1987). By purposefully controlling their attention, infants can regulate their own distress in this rudimentary way (see also Stearns, 1993). Parents may give support to this regulatory process, motivating attention and social interaction, by providing interested, happy faces and voices to infants, even in situations where the infant is distressed (Malatesta & Haviland, 1982). These processes are relatively well delineated but the focus has been exclusively on the roles of auditory and visual sensory systems in mood and attention regulation. The olfactory system, with its connection to the VTA, is at least as likely, if not more, to provide mood regulation early in life. The current study seeks to clarify the role of olfaction in emotion regulation as it affects attention. 1.3. Olfaction in infants Newborns can attend to and localize odors (Bingham et al., 2007 and Doucet et al., 2007). They are capable of detecting a variety of biological and artificial odors (Goubet et al., 2002) including their own mother's breast milk and amniotic fluid (Bingham et al., 2007, Doucet et al., 2007 and Varendi et al., 1998) and quickly avoid anise and other unpleasant odors (Schaal et al., 2000 and Soussignan et al., 1997). Infants not only localize the source of odors, but also will orient preferentially to familiar ones (Marlier and Schaal, 2005 and Schaal et al., 1998). 1.4. Olfaction and mood regulation Part of the significance of these early skills is related to the unique connection of the olfactory system to the VTA area, which is a main producer of dopamine and is presumed to be an important part of mood regulation, particularly positive mood regulation (Ashby et al., 1999). This relationship between olfaction and mood regulation has been demonstrated in infants during various medical procedures. Varendi et al. (1998) recorded crying in neonates during a 90-min observation period immediately after birth, while they were exposed to either their own amniotic fluid, their mother's breast odor (obtained prior to giving birth) or to a no-odor control. Babies presented with their own amniotic fluid cried less than babies in either of the other conditions. In another study, different groups of infants undergoing a routine (painful) heelstick to draw blood were exposed to an odor (vanillin, commonly rated as pleasant by adults) to which they had been familiarized, the same odor to which they had not been familiarized, or no odor. The blood draw was prescribed by the physician as part of the infants’ routine care. Infants in the first group were familiarized with vanillin overnight. A short while later, a scarf scented with vanillin was held next to the infant's nose while the blood draw was performed. Infants in the other groups were not familiarized, but a vanillin-scented or unscented scarf was held next to their noses during the blood draw. Babies presented with the familiar odor cried less during the less painful procedure (venipuncture) and recovered (return to baseline levels of crying and grimacing) more quickly after the more painful procedure (Goubet, Rattaz, Pierrat, Bullinger, & Lequien, 2003). The authors concluded that familiar odors can reduce distress when a neonate is stressed and in pain. Similar effects have also been reported for unfamiliar odors. Kawakami and colleagues exposed neonates to the artificial odors of lavender or milk or to no odor during the routine heelstick procedure (Kawakami et al., 1997). Infants in the odor groups demonstrated less salivary cortisol in response to the heelstick than did infants in the no odor control condition. The authors concluded that odor influenced cortisol response during stress. 1.5. Support against stress Following the Goubet et al. (2003) and Kawakami et al. (1997) studies showing the calming effects of odor in a stressful environment, we predict that exposure to a pleasant odor before and during a stressful event (e.g. watching sad female face and voice) also will be calming, leading to increased attention. In the case of infants the pleasant odor should result in fewer negative emotional reactions, i.e. fewer cry faces or self-comforting mouth movements (Haviland & Lelwica, 1987). Additionally, attention, i.e. looking time, to the stressful sad video should also be increased. In other words we predict that the pleasant odor increases the infants’ coping with stress, affecting both cognitive (attentive) and emotional processes. Our prediction of infants’ stress reduction during a stressful experience when exposed to pleasant familiar odors may be similar to the effect of positive emotion as described by Fredrickson and Levenson (1998). They first presented adults with either a positive audio/visual emotion stimulus (contentment and amusement) or comparable neutral or sad stimuli, after which the adults watched a fear-inducing film which increased their heart rates. Those who first saw the positive video recovered more rapidly from the cardiovascular effects of the fear induction. In other words, those individuals who first were exposed to a positive, supportive video followed by a threatening one, returned to their pre-stress levels of cardiovascular activation more quickly. In addition there are numerous studies indicating that adults’ positive mood allows them to focus on relevant negative information during a task (e.g., Aspinwall, 1998 and Trope and Neter, 1994). 1.6. Attention moderation Infants’ attention is readily affected by a variety of object characteristics which may interact. The emotional valence or familiarity of the object of attention (Kahana-Kalman and Walker-Andrews, 2001 and Montague and Walker-Andrews, 2002), the contrast of positive and negative objects presented in succession (Nelson, Morse, & Leavitt, 1979), and the specification of the object in several modalities (Caron, Caron, & MacLean, 1988) all have varying effects on the amount of attention displayed by the infant. The positive valence of an audio/visual signal increases looking time generally (hence our prediction that a pleasant olfactory signal may also increase looking time). Infants usually display more positive behaviors (smiling, approach behaviors) to happy expressions and more negative behaviors (frowning, avoidance behaviors) to angry expressions (Montague and Walker-Andrews, 2001 and Serrano et al., 1992). They also look away when their mother demonstrates negative affect and continue to attend (look forward) when she smiles (Haviland & Lelwica, 1987). Infants attend longer to positive than negative emotional expressions from an early age. The current study examines whether odor can moderate attentional processes typically engendered by the emotional valence of the audio–visual stimuli being presented. To determine whether the presence of odor affects infant attention, we put a small pad on the shirt of 6-month-olds. The pad had no odor or a small, measured quantity of manmade scent, one a “floral powdery” scent often used in baby lotions and powders and the other a fresh pine or evergreen scent often used in “fresh pine” lotions, shampoos and cleansers. The pads were attached to the infants’ shirts just before they watched a sad and then happy (or vice versa) facial and vocal expressions. With this procedure we sought to determine whether odors affect mood even in the presence of the auditory–visual stimuli that typically elicit emotional responses, both positive (to the happy video) and negative (to the sad video). We predicted that infants exposed to odor would look longer overall than those not exposed to odor and infants exposed to odor would have more positive and fewer negative emotional behaviors than infants not exposed to odor.