Saturday, October 25, 2008

Week 6: Computational models of cognition and affect (Part 2)

Thagard, P. (2008). How molecules matter to mental computation. In P. Thagard (Ed.) Hot Thought: Mechanisms and applications of emotional cognition pp 115-131. Cambridge, MA: MIT Press.

In this chapter, Thagard argues that computational models of cognition need to consider the influence of neuromodulators at the molecular level. He argues for understanding processes in the brain as the result of both chemical and electrical activity. He goes on to point out that many of the chemical influences on synaptic activation occur as the result of activity of cells far removed from the local neural network, such as when the release of hormones influence distant synaptic firing. Much of the chapter goes into technical details of how chemicals such as hormones influence the action of neurotransmitters and synaptic activity, but the overall thesis is that if cognitive scientist are to construct accurate computational models, they must take into consideration the effects of chemical processes on the activation of these models, rather than approach them as if they were electrical computers. The effects of chemical processes, he argues, are even more important to consider in computational models of cognition as the evidence for the role of emotion in cognition mounts. Evidence already exists for the effects of hormones or other neuromodulators on emotion; therefore, these same chemical reactions ultimately affect cognition. He points out that while it may not be necessary to only consider systems at the molecular level, knowledge about molecular processes should be considered one type of map that is useful for certain levels of analyses – he presents the example that while a large map of Europe is useful for locating Switzerland as north of Italy, another type of map, more fine grained, is useful for navigating the terrain of the Swiss Alps. I would tend to agree that if a truly holistic account of cognition is to be developed, consideration of the molecular processes contributing to patterns of neural activation would only serve to enrich this development. While it might not serve cognitive science for researchers to try to attempt the formidable task of becoming expert in all levels of analysis, integrating findings from molecular and network levels of analyses would likely strengthen the understanding of cognition at both of these levels and strengthen a more holistic understanding.

Week 6: Computational models of cognition and affect (Part 1)

Wagar, B. M., & Thagard, P. (2004). Spiking Phineas Gage: A neurocomputational theory of cognitive-affective integration in decision making. Psychological Review, 111, 67-79.

In this article, Wagar & Thagard present a new computational model of cognitive-affective processing, called GAGE after the famous case of Phinneas Gage (whose personality changed dramatically after a tamping iron destroyed the left side of his brain, transforming him from a reliable, dependable and level-headed figure to an impulsive and profane individual). GAGE focus on the contribution of the ventromedial prefrontal cortex in gauging future consequences and behaving accordingly. Specifically, the VMPFC has been implicated in the ability to refrain from behavior leading to an immediate reward if that behavior has future negative consequences, or delaying immediate reward for a future, larger reward. In the GAGE model, Wagar and Thagard examine how the VMPFC and amygdala interact with the hippocampus to coordinate potential responses with bodily states associated with the current situation and contextual information about the situation. They were particularly interested in the mechanism by which context has a moderating effect on emotional reactions to stimuli.
Their model is an extension of A. Dimasio’s (1994) somatic marker hypothesis, whereby feelings or emotional states become associated with long-term outcomes of certain responses to a given situation. The VMPFC is thought to play an important role in generating somatic markers. In this hypothesis, sensory representations of a response to a current situation activate knowledge about previous emotional experiences in similar situations. These markers act as biases influencing higher cognitive processes that coordinate responses. Wagar & Thagard extend on this by suggesting four key brain structures involved in this process. First, the VMPFC responds in concert with the amygdala. However, Wagar & Thagard suggest the mechanism by which the amygdala response (or immediate emotional response) versus the VMPFC response (based on potential outcomes of responses) wins access to higher cognitive processing is through gating by the nucleus accumbens, which in turn gates information based upon contextual information received from the hippocampus. The process is hypothesized to unfold as such: 1) the VMPFC receives input from sensory cortices, representing behavioral options; 2) the VMPFC also receives input from limbic regions, providing information about internal bodily states, most notably from the amygdala; 3) the VMPFC records signals defining a given response by encoding representations of the stimuli and comparing it to the behavioral significance of somatic states that have been previously associated with the response; 4) the VMPFC generates a “memory trace” representing the action and expected consequences of that action; 5) through reciprocal connections to the amygdala, the VMPFC elicits a reenactment of bodily states associated with the specific action; 6) this covert emotional reaction is passed on to overt-decision making processes – however, the transmission of this information is gated by the NAcc, as controlled by the hippocampus, as 7) the hippocampus controls VMPFC and amygdala throughput by depolarizing the NAcc based upon context – the NAcc allows only activation signals from the VMPFC and amygdala through that are consistent with the current context allowing spike activity in the NAcc. As staed in the article, “The hippocampus influences the selection of a given response by facilitating within the NAcc only those responses that are congruent with the current context (p.70).”
This is where the article loses me a bit, because I am not entirely certain by what process the hippocampus is purported to match current contextual information with memory traces about past contexts, as generated by the VMPFC, in order to chose which potential response information to allow through. For example, given the tendency for individuals with anxiety and mood disorders, and particularly trauma, to misread the current contextual information, this would be an important part of this process to understand. Individuals who have experienced trauma, for example, show a tendency to disproportionally map past representations onto current contexts. If Wagar & Thagard are suggesting the hippocampus is matching current context to past memory traces, this would imply individuals with trauma have deficits in the ability of their hippocampus’s to accurately gauge the current context. (However, perhaps it is the result of affective influences on sensory processing, such that information about the current context is distorted, and thereby may match memory traces more closely.) In addition, while I can understand the mechanics of this proposed process, it leaves me with open questions about the hippocampus’s “motivation.”
Nevertheless, Wagar & Thagard go on to present evidence from two studies of the GAGE model. The goal of the first study was to see if GAGE could simulate the experimental results of the Iowa gambling task in Bechara et al., 1994. In this task, participants are given a choice of four decks and are asked to make series of card selections from each of the four decks. They are given $2,000 as a loan to start, and play the decks to try to capitalize on this loan. “Bad” decks give immediate rewards, but long-term net losses, whereas “good” decks give larger delayed rewards and overall net gain. The results from the initial experiment showed normal participants quickly adopted a strategy of pulling cards from the good decks, thereby demonstrating the ability to delay reward for greater ultimate gains. By contrast, participants with VMPFC lesions never learned this strategy, and continued to act upon immediate rewards without regard to future consequences. In the current study, Wagar & Thagard trained GAGE on this same task. When the VMPFC was taken out of the model, GAGE acted only upon immediate reward, whereas leaving the VMPFC in the model resulted in more selections from “good” decks and greater overall gains. In essence, without the influence of the VMPFC, the computer was acting upon emotional reactions elicited by the amygdala and reflecting the immediate situation. When the VMPFC was included, decisions were based upon potential outcomes, not immediate affective appraisals. VMPFC and amygdala responses were modulated by gating of the NAcc, which in turn was modulated by the hippocampus, in line with the proposed model above.
In a second study, the goal was to simulate the role of context in the integration of physiological affective arousal and cognition; specifically, the mechanism by which context moderates emotional reactions to stimuli. They had the machine gauge emotional reactions as positive or negative while in a positive versus a negative context. The results of this study showed that when the NAcc was presented with two possible VMPFC representations, the hippocampal-derived context drove GAGE’s behavior, such that positive contexts elicited positive responses and vice versa. The researchers go on to suggest that the NAcc stores associations between VMPFC and hippocampus to elicit representations based on the current context.
The two studies are summarized as such: Study 1 demonstrates that “the VMPFC and the amygdala interact to produce emotional signals indicating expected outcomes and that these expected outcomes compete with immediate outcomes for amygdala output…temporal coordination between the VMPFC and amygdala is a key component to eliciting emotional reactions to stimuli (p. 76).” Study 2 demonstrates that context exerts an effect on cognitive-affective integration, such that “For the signals from the VMPFC and the amygdala to access brain areas responsible for higher order reasoning, context information from the hippocampus must unlock the NAcc gate, allowing this information to pass through (p.76).” These conclusions lead to a few questions. First, does this suggest that the hippocampus overrides potential outcome decisions presented by the VMPFC? In other words, if the VMPFC is creating memory traces based on past experiences in similar situations, is it the case that the VMPFC is assuming one context that the hippocampus either rejects or confirms? Do the context appraisals formed by the hippocampus represent contextual memories or the actual current context? And how does the hippocampus form judgments about the current context, unless it is comparing it to prior encounters with the context? Isn’t contextual memory formation a key function of the hippocampus? There seems to be almost a memory loop going on here – the VMPFC is taking in sensory information and judging appropriate behavioral responses based upon the behavioral outcome of past encounters with the stimuli – which would imply some form of contextual representation. This information then is gated by the way in which the hippocampus judges the current context, and whether the information presented by the VMPFC is matching this judgment. The hippocampus encodes contextual memories about past encounters with the current context, which you would think influences the VMPFC’s initial representations. Is this process more dynamic than the GAGE model is implying?

Friday, October 24, 2008

Week 5: Language Acquisition and Processing (Part 2)

Jia, G., Aaronson, D., Wu, Y. (2002). Long-term language attainment of bilingual immigrants: Predictive variables and language group differences. Applied Psycholinguistics, 23, 599-621.

This article presents a study in which the long-term attainment of a second language, specifically factors relating to long-term L2 decline, was explored. The study sought to answer four main questions: 1) Given long-term L2 attainment decline versus long-term L1 increase, which aspects of language proficiency and to which bilingual groups can the findings be generalized; 2) what are the mechanisms leading to the switching or maintenance of dominant language between young and older arrivals; 3) what environmental or affective variables might be involved; 4) are their differences apparent in other groups previously studied, namely Chinese-English and Spanish-English, and are there additional social or cultural variables influencing differences in attainment between bilingual groups above and beyond language distance. To answer these questions, the study 1) investigated grammatical proficiency of 44 Mandarin-English speakers to investigate the relationship between long-term L1 and L2 attainment; 2) using a language background questionnaire, explored additional social, environmental, and affective variables; 3) collected normative data on L1 proficiency for Mandarin monolinguals between the ages of 9-16 to compare relative L1 proficiency between bilinguals and their monolingual counterparts; and finally, 4) gathered data on long-term L2 attainment of other groups to examine generalizability of results to other bilingual groups (specifically, Korean- Mandarin- Cantonese-English and European English bilinguals).
In the initial study, participants were presented with a listening and a reading task designed to assess judgments about grammaticality of sentences. Each task was presented in both English and Mandarin. Judgments in English included morphology (past tense, plurals, third person, present/past progressive, etc.) and syntax (articles, predicate structures, particle movement, pronominalization, etc.). Judgments in Mandarin included word order, inappropriate insertion of words, and inappropriate omission of words. Both grammatically correct and incorrect sentences were presented. Results showed younger AoA was associated with higher accuracy on the English listening and reading task and lower accuracy on the Mandarin listening task. There was also a negative correlation, such that better performance on L2 was associated with poorer performance on L1. Higher performance was also associated with self-report ratings of proficiency in both L1 and L2. This study also assessed environmental and cultural variables. Higher performance on the English listening and reading tasks was associated with younger AoA and more years of education in the U.S., but not length of time in the U.S. Better performance on the English listening task was associated with with more frequent usage at home, as well as more people speaking English at home. Better performance on the Mandarin task was associated with less frequent usage of English, and less people speaking English, at home. The variance between L1 and L2 proficiency was also associated with the level of the speaker’s mother’s proficiency in English, such that the more proficient the mother is in speaking English, the more proficient the children are. Looking at the normative data for comparable level of proficiency in Mandarin between bilinguals and Mandarin monolinguals, the bilinguals tended to arrive with less than adult proficiency in Mandarin. The authors suggest future studies should examine whether level of L1 proficiency in early learners has an effect on L2 acquisition.
Examining the generalizability of these results with other bilinguals, Asian language speakers evidenced stronger AoA effects and significantly lower accuracy on the listening and reading tasks than European language bilinguals. This finding is in line with the proposals of Hernandez and Li, wherein the lexical difference between L1 and L2 influences levels of lexical attainment, as is evident in greater AoA effects in Chinese-English bilinguals than in Spanish-English bilinguals.
In general, the results of this study show individuals who immigrate at a young age tend to switch dominant languages from L1 (Mandarin) to L2 (English), whereas older immigrants tend to maintain their dominant language. However, the maintenance of L1 as the dominant language was influenced by the extent to which English was spoken at home. This suggests it is not merely AoA effects on the ability to acquire the lexical aspects of L2 that prevents greater L2 attainment, but perhaps a combination of factors, including the extent to which the “language of life” is expressed in L2 rather than L1. Thinking back to Harris, Gleason, and Aycicegi (2006), it would be interested to see the extent to which a late learner who is immersed in the L2 language and culture, such as being married to a native speaker, would have less difficulty detecting grammatical errors than a late learner who remained in a household where L2 and accompanying cultural practices were intact. However, this again makes me think of my own step-mother, who would very likely have great difficulty detecting all the grammatical errors in a listening task. If she performed poorly on the tasks in this study, one could assume AoA effects in her ability to acquire English are present to a large extent. She is an individual who speaks L2 to her husband, her children, her step-children, her coworkers, and her friends on a daily basis – in other words, her language of life has been English for the last 25 years of her life. The only remaining contact she has with L1 is in conversations with her sisters. Despite the length of time she has been in the U.S. and living in an English speaking household, she is less than proficient in her ability to speak English, particularly in her pronunciation of English words which, according to this study, would have resulted in lower attainment by her eldest daughter, which did not prove to be the case. However, her eldest daughter was only six when she arrived, and was less than proficient in Vietnamese. Her daughter’s superior attainment of English (such that she sounds no different than a native speaker) fits with the conclusions of this study that younger immigrants tend acquire L2 to a higher proficiency and even switch dominant languages from L1 to L2, and perhaps her younger age of arrival cancels out the effects of her mother’s lower language proficiency.
In sum, this study, by focusing on differences in grammatical ability, lends support to the proposal by Hernandez and Li (2007) that perhaps AoA effects are the result of a critical period for sensorimotor processing, which in turn affects the ability to discern lexical differences between L1 and L2, and therefore affects grammatical accuracy and attainment in L2. It would be interesting to see further studies of late learners, in which differences in environmental and social factors and their relationship to overall L2 attainment are explored.

Week 5: Language Acquisition and Processing (Part 1)

Hernandez, A.E., & Li, P. (2007). Age of acquisition: It’s neural and computational mechanisms. Psychological Bulletin, 133, 638-650.

This article explores possible neural and computational underpinnings of AoA effects, and presents an argument for specific aspects of language acquisition that are more susceptible to AoA effects. Hernandez and Li first present a few of the existing theoretical accounts of AoA. Brown and Watson (1987) propose AoA effects in word learning are the result of “phonological completeness,” whereby early-learned words are stored holistically (thus more easily retrieved), while late-learned words are fragmented and need to be reconstructed. However, this theory has been disputed based on the fact that in a segmentation task reaction times were found to be faster for early-learned words than late-learned words, which the authors suggest is counter to what should be the case if the late-learned words were already fragmented. (This argument was a little difficult to follow simply because the article does not explain what a “segmentation task” actually is.) Another theory of AoA effects is the “cumulative frequency” hypothesis. This theory proposes early-learned words are more easily accessed because of the additive effects of their frequent usage over time. Late-learned words, according to this theory, would have been encountered less frequently and therefore would be less easily accessed. However, research in older adults did not find AoA effects of specific words to increase with age.
Another theory is the “semantic locus hypothesis,” which posits that early-learned words have semantic advantage over late-learned words because they are represented in the semantic network first, and affect the way later learned words are semantically processed. This would suggest a semantic “map” that is formed to early words and affects later words. Hernandez and Li point out that, if this was the case, bilingual speakers would match semantic concepts to two separate forms, that AoA would transfer from one language to the next, and that L2 lexical items should inherit L1’s lexical AoA. This does not turn out to be the case, however, as L2 lexical speed is associated with the age at which the word was learned in L2 and not the corresponding age it was learned in L1. For the semantic locus hypothesis to work, therefore, there would have to be separate semantic stores for each language. Hernandez and Li therefore suggest AoA exerts effects at the lexical level, not the semantic level. Further, evidence from computational modeling reviewed in the article suggests increased rigidity in word learning with age, which would be more suggestive of AoA effects at the lexical level, since one could assume semantic processing would be more enriched with age given the increased capacity to manipulate concepts and infer semantic meaning as one gets older.
The article goes on to present some intriguing evidence from neuroimaging studies of increased activation of Heschl’s gyrus, implicated in auditory processing, when making lexical decisions to early learned words, whereas increased inferior prefrontal cortex activation, implicated in effortful activation of semantic meaning, is evidenced for late learned words. The authors suggest this may represent a reliance on auditory processing for early learned words and a reliance on semantic processing for late learned words. If the lexical/semantic distinction in AoA is correct, this would make sense, in that early encoding of lexical information would involve increased reliance upon auditory processing to detect subtleties between phonemes and morphemes in phrase construction in order to learn lexical rules. In line with this, another study cited in the article found that participants coactivated auditory representations when making lexical decisions pertaining to early learned words, even though these words were presented visually. Hernandez and Li conclude that the neural substrates of early learned lexical information appears to represent more automatic processing, whereas late learned words require additional processing, mapping lexical information onto semantic information.
This has interesting implications for the learning of a second language. Hernandez and Li review studies that have investigated semantic and lexical processing between L1 and L2. In neuroimaging studies, tasks involving syntactic processing evidenced greater AoA effects than tasks involving semantic processing. In a study of Chinese-English bilinguals, in which individuals read sentences containing syntactic violations, differences between bilinguals and native speakers arose for both syntactic and semantic violations, but were apparent at different ages. Differences between L2 learners and native speakers in the detection of syntactical violations appeared in participants who had learned English as early as 2 years of age, whereas detection of semantic violations appeared only after age 11. In addition, late learners rated themselves as less proficient in L2. Another study found increased activation relative to early learners in areas implicated in motor planning and articulatory effort when late learners of L2 processed grammatical violations, suggesting early learners were able to process words more automatically whereas late learners required additional, more effortful processing. These differences were not found in semantic processing, and instead differences in semantic processing were only found when comparing late learners with high proficiency to late learners with low proficiency. The authors suggest, therefore, that AoA effects exist for grammatical violations, whereas proficiency is associated with semantic violations. Further, the article goes on to discuss how the magnitude of AoA effects in L2 acquisition are greatest when the differences between L1 and L2 are large. For example, AoA effects in judging grammatical errors in Spanish-English learners are smaller than AoA effects in judging grammatical errors in Chinese-English learners.
The authors suggest this difference in the magnitude AoA effects is the result of the ability to detect subtle differences in syntax between the two languages, or what would constitute a syntactic violation in L2, which require phonological and articulatory demands, which in turn require a certain level of auditory and motor processing. They argue that it is here where AoA exerts its effects – that perhaps the “window” for learning lexical aspects of a second language has more to do with sensorimotor processing. They relate this to the critical period evidenced in the development of sensorimotor processing in visual domains, and in the behavioral and neural domains of learning music (perfect pitch; synchronization of motor movements to visual presented stimuli). They posit that language, in essence, reflects a sensorimotor ability. Because areas involved in sensorimotor processing undergo rapid organization and reorganization early in life, and evidence a loss of plasticity, perhaps the difficulty a late learner of L2 has in mastering the subtleties of L2 (such as noun-verb agreement in Chinese-English speakers, or verb irregularities in Spanish-English speakers), is the result of reduced plasticity in processing and articulating these subtle differences. The study by Jia, Aronson, & Wu reviewed in the next posting lends further support to this hypothesis.
I immediately think of my own step-mother, who came to America in 1975 from her native Vietnam. After 33 years speaking English and 25 years living with an English-speaking husband in an English-speaking household, she has an excellent grasp of the semantics of English, and has even written books and poetry about her experiences using English. However, she still struggles with the grammatical subtleties of English, such as dropping the last sound of words, using correct noun-verb agreements, or using the wrong verb form in sentences. By contrast, her oldest daughter, who was 6 years old when they arrived in America, has no trace of a Vietnamese accent, and sounds no different than a native speaker of English. This account may also lend support the emotional context of learning hypothesis of Harris, Gleason, and Aycicegi (2006) reviewed in the last posting: One could argue that regardless of the ability to master the grammatical or lexical aspects of language, the ability to master the semantic aspects of a second language continues throughout life, and grasping the semantic meaning would also imply a relating of that meaning to the self through emotional processes. Therefore, one could develop a richer emotional connection to certain words from L2 learned late, and a critical window for pairing emotion and words may not necessarily exist. Instead, as Harris, Gleason & Aycicegi (2006) suggest, it may be the case that the greater emotional salience of early learned words accounts for differences found between the emotional intensity of reprimands in L1 versus L2, rather than AoA effects being at play.

Wednesday, October 22, 2008

Week 4: Special Topic: Affect and language

Harris, C.L., Gleason, J.B.,& Aycicegi, A. (2006). When is a first language more emotional? Psychophysiological evidence from bilingual speakers. In A. Pavlenko (Ed.), Bilingual minds: Emotional experience, expression, and representation. Clevedon, United Kingdom: Mulilingual Matters.

In this article, Harris and Gleason move away from computational accounts of language acquisition in bilingual speakers and consider the role of emotion. They note that, traditionally, investigations into the emotional and subjective experiential accounts of language has been shunned due to the idiosyncratic nature of emotion, which runs counter to a research agenda that seeks to identify the universality in linguistic processes. However, Harris and Gleason point out that there is significant overlap in subjective accounts of language, and that the subjective quality of specific experiences can be very similar across individuals. They point to consistent results found in recent research conducted by Dewaele (2004), in which greater emotional intensity was endorsed when speakers used taboo in their native language than in a second language. Harris and Gleason also point out that when emotion has been considered in psycholinguistics, it has been thus far limited to investigations of monolingual speakers. The article goes on to review recent studies conducted by the authors further investigating the role of emotion in bilingualism – specifically, are utterances in L1 more emotionally arousing than utterances in L2?
In a series of studies, the authors use psychophysiological measurement (SCR) in conjunction with self-report to investigate emotional responses to specific phrases. SCR was chosen as these responses are generated not only to threat but also indicate the degree of relevance a specific stimulus holds for the individual. In the first study, participants included native Turkish speakers residing in the U.S. Participants were presented with a series of phrases in both L1 (Turkish) and L2 (English) that included taboo words, reprimands, aversive words, positive words, and neutral words. Whereas emotional reaction to taboo words was high in both Turkish and English, the greatest difference in responding was found for reprimands. The authors suggest the greater emotional responsivity to reprimands in L1 may be the result of the emotional environment in which these phrases were initially learned. Research suggests conversational aspects of autobiographical memory may be encoded in a specific language, and memories of being reprimanded may therefore be encoded pairing specific words with their emotional contexts. The authors also point out that language acquisition occurs in the same years as the development of emotion regulation. Reprimands by parents may elicit highly emotionally-charged responses from the child, as maintaining attachment relationships with the parent (i.e. not jeopardizing this relationship through wrongdoing) is a paramount motivational goal. Memories of reprimands, therefore, are encoded as highly emotionally salient events. Following research on emotion and memory, it is likely that specific words are paired as emotionally relevant auditory stimuli that become associated and encoded as emotionally salient. In support of this, greater responses in this study were elicited when participants were presented with reprimands in L1 (Turkish) as auditory stimuli than as visual stimuli. As these reprimands are generally heard first before being read, and reading reprimands may not occur within as emotionally-charged a situation as hearing them, the visual stimuli of written reprimands may not have been encoded in memory with the same degree of emotionally salience.
In a second study, Spanish-English bilinguals were included and categorized according to age of acquisition: early learners (born to immigrant parents and learned English around age 5); balanced bilinguals (arrived in America around age 6 or 7); and late learners (learned English around age 12). The early learners endorsed English as their most proficient language, balanced bilinguals endorsed both, and late learners endorsed Spanish. Similar to the first study, the greatest difference in L1 relative to L2 responses was found to reprimands, but only for the late learners. Further, the emotional arousal of L2 was weaker than L1 only for those who acquired L2 past the age of 7. This suggest a decline in the emotional significance of L2 as a function of both age of acquisition and degree of proficiency in L2.
To investigate whether one language in these studies was inherently more emotional than the other, a third study investigated ratings of emotional intensity of phrases in Spanish versus English through a questionnaire study involving both American and Colombian students. This study found items rated similarly. However, another study conducted by the authors found native Turkish speakers rated Turkish phrases higher than English speakers rated the English counterparts. The authors suggest cultural differences may exist in the approach to these ratings, wherein baseline ratings are higher or lower dependent upon culture. This is an important observation, however the article does not tie this finding back to earlier investigations of American and Colombian students, so it is unclear if similar effects exist between Spanish and English speakers in these cultures.
The article goes on to explore possible reasons why a first language might be more emotionally forceful than a second language. A few psycholinguistic theories are reviewed, such as Johnson and Newport’s theory of a maturational mechanism in which genes for acquiring language are expressed more strongly in early childhood. This would suggest the affective primacy of L1 is related to a general language acquisition mechanism that is present in early in life. Birdsong came to different conclusions, pointing to motivational factors. It is interesting to note, however, that both of these lines of research are investigating grammatical knowledge, and are investigating very different L1 languages. Johnson and Newport investigated Korean- and Chinese-English speakers, whereas Birdsong investigated Spanish-English speakers. As will be explored in a review of Hernandez and Li (2007; see separate post), the differences found in between these investigations may have more to do with the lexical difference between L1 and L2 than differences in affective or semantic significance. In other words, if two languages are more grammatically similar, differences in grammatical knowledge as a function of age of acquisition might be less distinct as differences accounted for by levels of motivation or length of time speaking. In contrast, languages that are grammatically very different might evidence greater AoA effects if, as Hernandez and Li suggest, an AoA effect exists for acquisition of syntax in L2 (such that acquiring L2 syntax is easier as a function of age). This point will be explored further in a separate post.
Returning to the present article, another suggestion as to why L1 may be more emotionally salient is the fact that because early language development occurs in tandem with the development of emotion regulation, and therefore early words and phrases may have more connections with the amygdala, whereas later learned words may have more connections with cortical areas. However, recall the results of the studies above found greatest differences in emotional salience for reprimands. Perhaps the greater emotional intensity of early learned phrases have more to do with the more highly charged emotional context, whereas the same phrases learned later are less emotionally charged??
In line with this, Harris and Gleason propose a “context of learning theory” in which language has a distinctive emotional feel because it is learned and/or habitually used in a distinctive emotional context. Words and phrases become stored in memory in a context-dependent manner. They go on to present anecdotal evidence that L1 is not always the most emotional language. They point to stories of colleagues who have come to the U.S. to study and subsequently have remained in the U.S., getting married and starting families. These individuals report their second language (English) as feeling more emotional. The authors suggest that experiencing highly emotional events, such as having children in the context of L2 may result in L2 becoming more emotional. It would be interesting to test this hypothesis – using the same method in the studies above, it would be interesting to see if the presentation of specific words or phrases related to caring for children (such as “crib” “bottle” or “the baby is crying”) would be more emotional for these individuals in L1 or L2. In other words, would specific words or phrases accompanying these highly emotionally-charged experiences be encoded with more emotional significance much in the same way reprimands in childhood were found to be?
Harris and Gleason’s context of learning theory fits nicely with the Hernandez and Li article concerning age of acquisition. Harris and Gleason pose the question as to whether a maturational mechanism may be at play in the results reported above, such that first-acquired languages are always more emotional. However, they point out that the early contexts in which language is first acquired are also generally more emotional (for example, naturalistic settings tend to be more emotionally charged than classroom settings), which may play more of a causal role. In addition, if differences in the emotional force between languages are a function of maturational mechanisms, how would this account for the anecdotal evidence presented above, in which individuals who acquired a second language later in life nevertheless report L2 as feeling more emotional? An important consideration, however, is what specific factors of language are affected by age of acquisition (AoA), a point explored by Hernandez and Li (2007). AoA effects may be present only for syntax, and not for semantics, such that a “critical period” for processing syntactical information may occur early in life, whereas the processing of semantic information can occur throughout the lifespan. If this were to be the case, this would lend further support to Harris and Gleason’s argument that the greater emotional force of a first language has more to do with the emotional context in which the language was acquired and less to do with maturational mechanisms, because the syntax in the phrases presented in the studies above does not vary, only the semantic content. This would also lend support for why L2 might still be more emotional when learned late, if L2 is frequently used in highly emotional contexts. It seems more plausible that specific words and phrases become highly associated with specific emotional contexts and are encoded in memory as such. Again, to test this theory, it would be interesting to replicate the studies above using words or phrases congruent with highly charged emotional contexts experienced later in life, to see whether similar effects arise.

(n.b. - Further discussion of the Hernandez and Li article appears as a separate post.)