N400-like semantic incongruity effect in 19-month-olds: Processing known words in picture contexts Manuela Friedrich and Angela D. Friederici J. of cognitive neuroscience, 2004, 16:8, Sylvia Yuan October 13, 2005 Psych 593SG

Goal To investigate whether adult-like mechanisms of semantic integration, as indexed by N400, are present in 19-month-olds

N400 An index of semantic processing in adults (e.g., Kutas & Hillyard, 1980)

N400 semantic incongruity effect Semantically incongruous stimuli elicit greater N400 amplitudes than semantically congruous stimuli This reflects a greater effort at semantic integration for unexpected than expected stimuli Semantic priming prior to stimulus presentation can facilitate processes of semantic integration  a reduced N400

Adult-like N400 in children Picture-matching –7- to 10-year-olds, greater negative component at latency 400ms to non-matching pictures in picture pairs (Friedman et al., 1992) Processing visually presented words and pictures –10- and 11-year-olds, antN400 to word stimuli, dual anterior negativities (N350 & N430) to picture stimuli (Coch et al., 2002) Processing sentences with semantic anomalies –Visually stimuli: 7- to 12-year-olds (Holcomb et al., 1992) N400 decreased in both amplitude and latency with age –Auditory stimuli: 6- to 13-year-olds (Hahne et al., 2004) N400 slightly delayed for 6- to 8-year-olds

What about younger children? (Molfese, Morse & Peters, 1990) 14-month-olds Trained on two novel words (“gibu” & “bidu”) for two objects ERP responses on “mismatch” names: –An early negativity at 60ms –A positivity at 560ms No N400-like incongruity effect

Why the focus on N400 in young children? To learn about the neural mechanisms of early word learning To evaluate the potential of using N400 to investigate other aspects of children’s cognitive development Concepts, semantic memory

The present study Goal: to investigate whether an N400-like response can be observed in 19-month-olds to words presented in contexts Task: picture-word-matching –Congruous condition: picture-word match –Incongruous condition: picture-word mismatch ERP recording Comparisons of spatio-temporal distributions –Adults vs. children (19-month-olds) –Among children: high vs. low comprehenders

Stimuli Pictures –Colored illustrations of single objects 44 words –Basic-level words (mean item difficulty =78%) –Slowly spoken (mean word length: 1083 ms) –Each presented twice Congruous context – with a matching picture Incongruous context – with a non-matching picture

Procedure Participants were seated in front of a computer screen Session lasted 12 minutes

Trial structure 0 ms1000 ms2000 ms3000 ms4000 ms Picture onset Indef. article Target word “A…” “ball” (congruous) “duck” (incongruous)

Participants 20 adults (mean age 23.7 years) month-old German-monolingual children –25 additional children were tested but excluded for crying/excessive movement (13) and too many artifacts/too much non-looking (12) On average, children were looking to the monitor about 85% of the session Children were split into two groups by the median comprehended words (37): low vs. high comprehenders –To assess whether ERP effects are related to children’s comprehension of the presented words in the experiment

ERP recording Reference electrodes: left and right mastoids Trial exclusion: –Trials with a SD exceeding 40 μV (for adults) and 100 μV (children) in a 200ms time window were rejected –Mean number of trials accepted: 32 (out of 44)

Adults’ ERPs Figure 1

Adults’ spatial distribution of ERPs Figure 3

Spatial distribution of adults’ difference wave Figure 4 A prominent effect at central-parietal midline sites

Adults’ condition main effects Table 1

Summary of adult ERPs An early effect of condition at temporal sites ms: Congruous words more (-) than Incong. words  Word-processing is affected by picture contexts early on A broadly distributed long-lasting semantic incongruity effect ms: Incong. words more (-) than Congruous words Most prominent at centro-parietal sites Stronger & more extended in the right hemisphere Anterior regions are also involved  This spatial distribution matches that of the typical N400 effect in semantic priming paradigms

Children’s ERPs Figure 2

Children’s spatial distribution of ERPs Figure 3

Spatial distribution of children’s difference wave Figure 4 Negativity effect mostly in the left parietal & frontal areas

Children’s condition main effects Table 2

Summary of child ERPs An early effect of condition at lateral front sites 150 – 400ms: Congruous words more (-) than Incong. words  Word-processing is affected by picture contexts early on A broadly distributed long-lasting semantic incongruity effect ms: Incong. words more (-) than Congruous words At centro-parietal & frontal sites Possibly more contribution from the left hemisphere  The spatio-temporal distribution of the semantic incongruity in 19-month-olds differs from that in adults.

Comprehension groups Median for comprehended words: 37 (out of 44) Children were divided into two groups by the median: –High-comp. (N=27): group median 42, range –Low-comp. (N=28): group median 33, range 6-37

Results: high- vs. low-comprehenders Early context effect did not change between groups For the later negative incongruity effect, there were group differences: –High comprehenders: Earlier (starting 300ms) & in right hemisphere More negative to incongruous words

ERPs of high & low comprehenders Figure 5

Main condition effects High comprehendersAdults Table 3 Table 1

Spatial distribution of ERPs Figure 6 More negativity in R hemisphere for high-comprehenders

Summary of high- vs. low-comp. groups Low-comprehension group –a small semantic incongruity effect in the left hemisphere that occurs much later (from 700ms) High-comprehension group: –Much like adults: a large semantic incongruity effect starting early ( ms) stronger effect in right hemisphere –Unlike adults: frontal areas are more involved

Discussion Auditory-evoked response Adults: N1-P2 complex (adults) Children: early positive-negative waveform Early context effect: greater negativity for congruous words Earlier for adults ( ms vs ms) Not about better known vs. less known words (cf. Mills et al., 1993) Possibly reflects top-down priming that facilitates early phonological-lexical processing –Known primed vs. unknown primed words

Later incongruity effect (greater negativity for incong. words) First N400-like semantic incongruity effect in children under 2 years Stronger involvement of frontal areas in children may reflect: –enhanced image-specific semantic processing, and/or –increased processing load

Negative response in children to congruous words as well –stronger in low-comprehenders –may reflect child’s effort in accessing meaning of words Effect stronger in high- than in low- comprehenders  Effect reflects different semantic processing w/ cong. & incong. words, representing a child N400! Later incongruity effect (cont’d)

Comprehension group differences No difference in the early context effect –This suggests both groups were creating appropriate lexical expectations from picture –Differences between groups may lie in whether phono-lexical representations of presented words primed semantic representations (to be integrated) Hemispheric differences in the incongruity effect –These may reflect processing differences as a function of the child’s general language abilities (e.g., Mills et al., 1993)

High-comprehenders as fast as adults in incongruity effect –Possibly due to child-friendly stimuli or high- comprehenders’ knowing all (or most) word stimuli –Latency difference in low-comprehenders may reflect difficulties in perceptual & semantic processing Comprehension group differences (cont’d)

Conclusion 19-month-olds show a child N400 in response to hearing words that do not match pictured objects The strong involvement of anterior regions in children for the incongruity effect may reflect image-specific semantic processing. Adult mechanisms of semantic integration of words are present early on. Children’s comprehension abilities are reflected in strength, latency & hemispheric differences of the incongruity effect.

N400 in even younger children! 14-month-olds (N=30) Picture-word matching task, with words that one-year- olds already know Results: Early context effect –200 to 400ms –Congruous words more negative –Lateral front regions  Lexical expectations from pictures! N400-like Incongruity effect –400 to 1000ms, incong. words more negative –Mostly over central and parietal regions, some frontal  Semantic integration & influence of priming! (Friedrich & Friederici, 2005)

Questions Is it really easier to go from pictures to lexical- phonological representations of words, than from representations of words to semantic representations? What ERP components are observed for mismatch of grammatical gender of words to pictures? If the incongruous word and its preceding article were additionally of mismatching gender (to the picture), would one expect to see stronger and/or faster N400 semantic incongruity effect?