ludtke 2008

8/14/2019 ludtke 2008

1/16

Event-related Potential Correlates of Negation in aSentencePicture Verification Paradigm

Jana Ludtke1, Claudia K. Friedrich2,3, Monica De Filippis1,

and Barbara Kaup1

Abstract

& In a sentencepicture verification paradigm, participants were presented in a rapid-serial-visual-presentation paradigm

with affirmative or negative sentences (e.g., In the front of the

tower there was a/no ghost) followed by a matching or mis-

matching picture. Response latencies and event-related poten-

tials (ERPs) were measured during reading and verification. Anenhanced negative shift in the ERPs for the subject noun (i.e.,

ghost) in negative, compared to affirmative sentences, wasfound during reading. We relate this ERP deflection to en-

hanced processing demands required by the negative particleno. Although this effect suggests a direct impact of negation on

language processing, results for picture processing reveal that

negation is not immediately integrated into sentence meaning.When the delay of picture presentation was short (250 msec),

verification latencies and ERPs evoked by the picture showed apriming effect independent of whether the sentence contained

a negation. Unprimed pictures (foreground object not men-

tioned in the sentence) led to longer latencies and higher N400

amplitudes than primed pictures (foreground object men-

tioned in the sentence). Main effects of negation showed uponly in a late positive-going ERP effect. In contrast, when the

delay was long (1500 msec), we observed main effects of truthvalue and negation in addition to the priming effect already in

the N400 time window, that is, negation is fully integrated intosentence meaning only at a later point in the comprehension

process. When negation has not yet been integrated, verifi-

cation decisions appear to be modulated by additional time-consuming reanalysis processes. &

INTRODUCTION

Albert Einstein once said I have no special talents.

Usually, a short sentence such as this is not particularlyhard to understand, even though it contains a negation.

Negation is a linguistic operator that takes a whole prop-osition into its scope (in the example above, the prop-osition that the speaker has special talents). It therebyconstitutes a means to communicating that the state ofaffairs denoted by this proposition (called the negatedstate of affairs) does not hold for the situation underconsideration. Depending on the linguistic and situa-tional context, and/or the world knowledge of thelistener, an actual state of affairs may be inferred (in

the example above, e.g., the fact that the speaker ishighly talented in several respects; cf. Kaup, Zwaan, &Ludtke, 2007). Research has shown longer processingtimes and higher error rates for negative compared toaffirmative sentences (for overviews, see Kaup, Zwaan,et al., 2007; Ludtke & Kaup, 2006; Carpenter & Just,1975; Clark, 1974). Similarly, higher cortical activationduring the comprehension of negative compared to af-firmative sentences has been observed using brain im-

aging (Carpenter, Just, Keller, Eddy, & Thulborn, 1999).However, exactly what kind of additional processing is

required by negative sentences is still a matter of debate.Comprehension of negated sentences is differently

modeled by propositional theories and simulation ac-counts of cognitive processing. According to proposi-

tional theories, the higher processing demand comesabout because a negative tag has to be incorporated intothe meaning representation of the sentence, resultingin an additional level of propositional encapsulation(Carpenter & Just, 1975; Clark & Chase, 1972). Accord-ing to the two-step simulation hypothesis of negationprocessing (e.g., Kaup, Ludtke, & Zwaan, 2006; Kaup &Zwaan, 2003), the higher processing demand ref lectsthat the comprehender is creating two simulations when

processing a negative sentence: a simulation of the ne-gated state of affairs and a simulation of the actual stateof affairs. This hypothesis is based on the view that com-

prehension is tantamount to mentally simulating thestates of affairs described in the linguistic input (Fischer& Zwaan, in press; Glenberg & Kaschak, 2002; Barsalou,1999; Glenberg, 1997). When processing a sentencesuch as The door is not closed, the comprehenderpresumably simulates a closed as well as an open door.Negation is implicitly encoded in the deviation betweenboth simulations.

1Berlin University of Technology, Germany, 2University of Ham-burg, Germany, 3University of Konstanz, Germany

D 2008 Mass achusetts Ins titute of Technology Journal of Cognitive Neuroscience 20:8, pp. 116

8/14/2019 ludtke 2008

2/16

With regard to temporal characteristics of the com-prehension process, propositional theories are relativelymute. It is not stated explicitly whether the compre-hender in a first step represents the encapsulated prop-

osition and then applies the negation operator to it, or whether the complex negated proposition is createdright away. In contrast, the two-step simulation hypoth-

esis explicitly assumes that the comprehender firstsimulates the negated state of affairs and only at a laterpoint in the comprehension process turns attention ontothe simulation of the actual state of affairs. Negation pre-sumably is being integrated into the meaning represen-tation, once the comprehender is turning attention away

from the simulation of the negated state of affairs andonto the simulation of the actual state of affairs. Thus,according to the two-step simulation hypothesis, nega-tion is incorporated into the meaning representation ata rather late stage in the comprehension process.

Indeed, the results of a number of behavioral studiesindicate that negation is not incorporated into the rep-

resentation of the sentence meaning right away, but onlyat a rather late stage in the comprehension process. For

instance, the processing of a picture of an open door isfacilitated relative to a picture of a closed door only afterabout 1000 msec after reading the sentence The door is

not closed. This indicates that it takes comprehendersabout 1000 msec to integrate the negation into therepresentation of the sentence meaning, orin termsof the two-step simulation hypothesisto shift attentionaway from the negated and onto the actual state ofaffairs (Kaup et al., 2006; see also Kaup, Yaxley, Madden,Zwaan, & Ludtke, 2007; Kaup, Zwaan, et al., 2007;Hasson & Glucksberg, 2006; Kaup, Ludtke, & Zwaan,

2005; Giora, Balaban, Fein, & Alkabets, 2004).Interestingly, a number of event-related potential

(ERP) studies employing a sentence verification para-digm also indicate that negation is initially not integratedinto the representation of the sentence meaning. Inthese studies, participants read and verified true or falseaffirmative and negative sentences [e.g., (1)(4)], andERPs were recorded for the sentence-final words (Hald,Kutas, Urbach, & Pahrhizkari, 2004; Kounios & Holcomb,1992; Katayama, Miyata, & Yagi, 1987; Fischler, Bloom,Childers, Roucos, & Perry, 1983).

1 A robin is a bird:True Aff

2 A robin is not a bird:False Neg

3 A robin is a tree:False Aff

4 A robin is not a tree:True Neg

In all studies, for the affirmative as well as for the negativeconditions, the amplitude of the N400, a negative-going waveform peaking at 400 msec, was smaller when thefinal word of the sentence had a semantic relation to theword in grammatical subject position [(1) and (2)] than

when this was not the case [(3) and (4); Fischler et al.,1983; see also Kounios & Holcomb, 1992; Katayama et al.,1987]. The same effect was found when subject and final word had a relation according to general world knowl-

edge [as in (5); Hald et al., 2004].

5 Hawai is = is not tropical = cold:

From language-related ERP research, the N400 ampli-tude is known to be larger to words that are semanti-cally unrelated (vs. related) with preceding words (e.g.,Bentin, McCarthy, & Wood, 1985), with sentence con-texts (e.g., Kutas & Hillyard, 1980), with global discoursecontexts (e.g., Nieuwland & Van Berkum, 2006), or when there is no (vs. is) relationship between wordson the basis of general world knowledge (Hagoort, Hald,Bastiaansen, & Petersson, 2004). Enhanced N400 ampli-

tudes in the ERP are usually interpreted as reflecting ahampered semantic integration process during language

comprehension (for a review, see Kutas & Federmeier,2000). This seems to suggest that the N400 effectobserved in the studies reported above reflects a se-mantic integration mechanism that does not take nega-tion into account. In other words, N400 amplitudes forthe sentence-final word are enhanced in conditions inwhich this word is not primed (vs. primed) by the wordin the grammatical subject position, independent of

negation. From the perspective of the two-step simula-tion hypothesis, this priming effect is not surprising, butpresumably reflects that comprehenders at the time ofmeasurement are still engaged in the first simulationprocess, which is the same for affirmative (e.g., Hawai

is cold) and negative sentences (e.g., Hawai is notcold). Because comprehenders have not yet integratedthe negation into the meaning representation, negationdoes not influence the N400 amplitudes.

Regarding the proposed later integration of negation,former ERP studies are not conclusive. Despite the factthat negation did not have any direct influences on the

N400 amplitudes, participants verification accuracies inthese studies were clearly above chance. This tells usthat comprehenders did take the negation into account when verifying the sentences. Given the assumed lagwith which negation is being integrated into the mean-ing representation of the sentence, it seems plausiblethat negation modulates sentence processing and veri-fication relatively late in this paradigm, possibly not untilshortly before response preparation. In line with this

assumption, Fischler et al. (1983) reported a virtuallygreater positivity in the ERPs elicited by the sentence-final words in negative sentences compared to affirma-tive ones about 8001120 msec after word onset, whichfailed to reach significance. Also in the other sentenceverification studies with English materials, no direct ERPeffects of negation were being reported (Hald et al.,2004; Kounios & Holcomb, 1992), and the results of a

2 Journal of Cognitive Neuroscience Volume 20, Number 8

8/14/2019 ludtke 2008

3/16

Japanese study by Katayama et al. (1987) are difficult tointerpret. Word order in Japanese is subjectobjectverb(e.g., Robin bird is/is not [literal translation]1). Thus,it was the final verb phrase that decided whether the

sentence was affirmative or negative. Higher amplitudesof the P3 component to affirmative than to negative verbphrases were observed. However, this may reflect higher

frequency of usage of the affirmative verb phrase ratherthan semantic differences between affirmative and neg-ative sentences.

Taken together, former ERP studies with negated sen-tences basically revealed N400 priming effects. There wereno conclusive neuronal indications that negation is incor-

porated into sentence meaning. The fact that in previousERP studies the sentence-final word determined whetherthe sentence is true or false makes the interpretationextra difficult because sentence verification processes andsentence wrap-up effects (cf. Hagoort, 2003; Osterhout,1997) cannot be disentangled.

Aims of the Current Study

The present study was set out to characterize neuronalprocessing of negation using a sentencepicture verifi-

cation paradigm. Participants read sentences such as Infront of the X there is a/no Y and afterward viewed apicture that either depicted a Y in front of the X or an-other object in front of the X (for details, see Table 1). Incontrast to the ERP studies reported above, verificationis temporally distinct from comprehension in the pres-ent paradigm. Participants first read the sentence thatin itself is neither true nor false. Only when they later

view the picture can they start the verification process.This allowed us to manipulate the amount of time that

participants have available for comprehending prior to

verification. Accordingly, to obtain more informationregarding the time course of negation processing, wepresented the picture with two delays, either 250 or1500 msec after sentence reading.

In line with previous ERP research showing that pic-tures as well as words can elicit N400 components (Ganis,Kutas, & Serano, 1996; Nigam, Hoffman, & Simons, 1992),

we expect to observe N400 effects in the ERPs elicited bythe picture. Similar to previous ERP studies, we shouldobserve a negation-by-truth value interaction: N400 am-plitudes should be relatively low in conditions in whichthe picture is primed by the sentence. This should be thecase for the true affirmative and the false negative con-

dition (cf. Table 1). In contrast, N400 amplitudes shouldbe relatively high in conditions in which the picture is notprimed by the sentence. This is the case in the falseaffirmative and the true negative condition (cf. Table 1). Itshould be noted that this potential priming effect mayhave at least two sources. First, amplitudes may be rel-atively low in the primed conditions simply because the

depicted foreground object was mentioned in the sen-tence. Second, amplitudes may be low in these conditionsbecause, according to the two-step simulation hypothesis,

the comprehender has simulated the depicted state ofaffairs when processing the sentence: For affirmative sen-

tences, the depicted state of affairs in these conditionscorresponds to the described state of affairs. In the neg-ative conditions, it corresponds to the negated state ofaffairs, which presumably is being simulated first duringsentence processing (see above). In principle, thesepriming effects should be observed at both delay con-ditions because (a) mentioning should facilitate pictureprocessing even after a certain delay, and ( b) because

the comprehender in both delay conditions has simu-lated the depicted state of affairs in the primed but not

in the unprimed conditions. However, priming effects

Table 1. Sample Materials

Sentence Picture Relation Simulations Condition Primi

In front of the tower there is a ghost. Mentioned True affirmative Yes

In front of the tower there is a ghost. Not mentioned False affirmative No

In front of the tower there is no ghost. Not mentioned True negative No

In front of the tower there is no ghost. Mentioned False negative Yes

Ludtke et al. 3

8/14/2019 ludtke 2008

4/16

may be slightly attenuated in the long delay condition be-cause (a) the effect of a surface-level variable such asmentioning may decline over time, and (b) the simulationthat corresponds to the depicted state of affairs may no

longer be in the comprehenders focus of attention, ashe or she may have already shifted toward the simulationof the actual state of affairs (e.g., a tower with nothing in

front).2

More important to the goals of our study, we expectto find a main effect of negation in the ERPs elicited bythe picture. Considering that integration of negationtakes a substantial amount of time (see above), we pre-dict that negation will affect the ERPs differently for

the two delay conditions. In the short-delay condition,we expect that comprehenders have not yet integratedthe negation into the representation of the sentencemeaning before picture presentation. Accordingly, in or-der to solve the verification task, comprehenders mustmake up for the integration when the picture comes up.This can be expected to be rather time consuming. ERP

effects of negation are therefore probably associatedwith the planning of the appropriate response to the ver-

ification task. In order to track those response prepara-tion effects, special attention will be paid to late timewindows in the ERPs elicited by the picture. In contrast,

in the long-delay condition, comprehenders had enoughtime (1500 msec) to incorporate the negation into themeaning representation, before being presented withthe picture. Accordingly, they have available a morecomplex representation in the negative than in the af-firmative versions when the picture comes up. This com-plexity difference should be reflected in the ERPs elicitedby the picture, but this time in relatively early time win-

dows. Thus, in the long-delay condition, we predict thatnegation effects will occur in earlier time windows than in

the short-delay condition.Parallel to the ERPs evoked by the picture, we will also

collect response times in the verification task. Responsetime patterns should resemble the ERP effects. There-fore, we expect to find faster response times in theprimed than in the unprimed conditions at both delays, with the possibility that the resulting negation-by-truthvalue interaction effects being smaller in the long than inthe short-delay condition. Similarly, for the main effect

of negation, we expect to find effects in both delayconditions but for different reasons as described above.In the short delay condition, verification times fornegative conditions should be prolonged compared toaffirmative conditions because of the time-consumingretroactive integration process. In the long delay con-dition, the successful integration of negation beforepicture presentation leads to a more complex represen-tation compared to affirmative versions, which may also

be reflected in extended response times. However, it ispossible that the main effect of negation in the longdelay may well be smaller than the one in the shortdelay.

As a third goal of the present study, we will investigateeffects of negation immediately after the negation markeris being encountered during sentence comprehension.Our sentencepicture verification paradigm will allow us

to observe effects of negation in the electroencephalo-gram (EEG) during sentence comprehension, indepen-dent of any priming or verification processes. In contrast

to the reported ERP studies, the sentences we used are,by themselves, neither true nor false (see above). Affir-mative and negative versions of a sentence only differ with respect to whether the penultimate word of thesentence is an ein (a) or a kein (no). Hence,the strength of the semantic association between subject

and object is identical between conditions. This allowsus to explore the neurocognitive processing of the finalword of the sentence as a function of negation. As of yetthere are, to the best of our knowledge, no studies thatanalyzed ERPs evoked by affirmed or negated nounswithin sentence comprehension independent of primingand potential verification processes. Thus, no clearcut

predictions can be made regarding the differences inthe ERPs evoked by affirmed or negated subject nouns.However, it should be noted that potential negation ef-

fects that show up immediately after processing of thenegation marker would not be inconsistent with our hy-

pothesis of a delayed integration of negation into themeaning representation of the sentence. According tothe two-step simulation hypothesis, the reader first sim-ulates the negated state of affairs, but in doing so, heor she of course has to keep in mind that the sentencewas negative and that the simulated state of affairs doesnot correspond to the actual state of affairs. Thus, at the very least, negative sentences should lead to an addi-

tional memory load once the negation marker has beenencountered in the sentence.

To summarize, in this study we are interested in ERPcorrelates of negation, both during, as well as after sen-tence reading. During sentence reading, we are inter-ested in the effects of negation on the processing of thenoun that follows the negation marker in the sentence.After sentence reading, we are interested in the process-es by which negation is being integrated into the sen-tence meaning. Thus, the main focus of the presentstudy is not on syntactic but on semantic effects of

negation.

METHODS

Participants

Participants were 17 undergraduate students from the Uni-versity of Konstanz (9 women, 8 men), all native speakersof German with no discernible uncorrected deficits in hear-

ing or vision. They were paid for their participation. Onlyright-handed subjects were included, as ascertained bythe Edinburg Handedness Questionnaire (Oldfield, 1971).No participant had a neurological history. The data for


8/14/2019 ludtke 2008

5/16

one student were excluded because of technical problemsduring the experimental session.

Stimuli

Eighty experimental sentences were constructed. These were of the form Vor/Auf dem X ist ein/kein Y (In

front of/On top of the X there is a/no Y), with the sur-face structures of the two versions of a sentence onlydiffering with respect to the penultimate word that eitheraffirmed or negated the noun in the subject position(i.e., Y) [e.g., Vor dem Turm ist ein Geist (In front ofthe tower there is a ghost)/Vor dem Turm ist kein

Geist (In front of the tower there is no ghost)]. Forthe 80 experimental sentences, 11 different monosyllabicbackground objects (i.e., X ) were used [e.g., Turm(tower) or Tisch (table)]. Every background ob-ject was used seven or eight times. For the 80 experi-mental sentences, 80 different disyllabic subject nounswere used. Only nouns with masculine or neuter gender

were used so that the article was ein (a) or kein(no) for all sentences.

In addition, 80 black-and-white pictures (black graphicson a white screen) were constructed, each of which de-picted the situation described in the affirmative version

of one of the experimental sentences. All pictures weresuch that the two objects could be easily identified, andeach was scaled to a size of 200 by 150 pixels. Eachexperimental sentence was paired with two pictures,one depicting the situation described in the affirmative version (e.g., a picture of a ghost in front of a towerfor In front of the tower there is a/no ghost), and theother depicting a different object in front of the same

background object (e.g., a picture of a lion in front of atower). The combination of one sentence and two pic-

tures yielded four conditions for each item: true affirma-tive, false affirmative, true negative, and false negative, with the predicted priming being present in the trueaffirmative and the false negative condition but not inthe false affirmative or the true negative condition. Thecorrect responses in the verification task depended onthe version: True versions required a true response;false versions a false response. For 40 of the items, thedelay between sentence and picture was 250 msec, for

the remaining 40 items it was 1500 msec. Word lengthand frequency were balanced for the two delay conditionsusing an on-line dictionary of German (www.wortschatz.uni-leipzig.de).

Each participant saw all four versions of each of the80 items, resulting in 320 trials. Of these, 160 containedaffirmative and 160 negative sentences. Eighty of each ofthese were followed by a matching picture and 80 by amismatching picture (with 40 in the short- and 40 in the

long-delay condition). The 320 trials were divided intosix blocks including 56 (Blocks 1, 2, 4, and 5) or 48 items(Blocks 3 and 6). Each block included maximally oneversion of an experimental sentence, but a picture could

be presented twice in a block. For one half of the trialsin each block, the delay was short and for the otherhalf long. Each block included an equivalent number ofitems in the four conditions. The 11 background objects

were divided over all six blocks. Short breaks were be-tween the blocks.

This produced a 2 (delay: short vs. long) 2 (nega-

tion: affirmative vs. negative) 2 (truth value: true vs.false) design, with repeated measurement on negationand truth value. Delay was manipulated within partic-ipants but between items. It should be noted that withthis statistical design, the predicted priming effects arepresent in case a negation-by-truth-value interaction is

being observed whereby the true affirmative and the falsenegative conditions should be associated with lower N400amplitudes and response times than the false affirmativeand true negative conditions.

Procedure

Participants sat in a sound-attenuated booth. The mate-rials were displayed using the software Presentation(Neurobehavioral Systems, www.neurobs.com). Each

trial began with a blank monitor for 2000 msec followedby a fixation point for 500 msec. Then the sentence was

presented word-by-word in the center of the screen,with each word being presented for 300 msec followedby a blank screen for 300 msec. After the final wordof the sentence, a fixation cross appeared for 250 or1500 msec depending on the trials particular delay con-dition. Finally, the picture was presented for 250 msec.Participants indicated as quickly and accurately as pos-sible whether the picture was true of the sentence just

read. Half the participants made true responses withtheir left thumb and false responses with their right

thumb. For the remaining participants, response hands were reversed. Participants were not given feedbackon their responses. After the picture disappeared, par-ticipants had a maximum of 4000 msec to react. If noresponse took place, the next trial started. Each test ses-sion started with a practice block of 24 trials, in whichparticipants received feedback on their responses.

ERPs were recorded continuously from Ag/AgCl elec-trodes held in place on the scalp with an elastic cap

(Electro-Cap, Germany). Scalp locations included 62 stan-dard locations according to the 1010 system (Chatrian,Lettich, & Nelson, 1988). Two additional electrodes were placed below both eyes. All electrodes were on-line referenced to Cz. Average reference was used foranalysis of ERP data. All electrode impedances were lessthan 5 k. EEG was recorded with a sampling rate of250 Hz.

Data Analyses

Response latencies and ERPs were calculated for correctresponses. Latencies and error rates of experimental

Ludtke et al. 5

8/14/2019 ludtke 2008

6/16

trials were submitted to two 2 (delay) 2 (negation) 2 (truth value) analyses of variance (ANOVAs), withrepeated measurement on all variables in the by-partic-ipants analyses but on only the latter two in the by-items

analyses. One of these ANOVAs was based on participant variability (F1 ), the other on item variability (F2 ). Indetermining outliers, we employed a two-step proce-

dure: First, the reaction times of each participant wereconverted to zscores. Then reaction times with a zscoredeviating more than 2 standard deviations from themean z score of the respective item in the respectivecondition were discarded. This eliminated less than 3.8%of the data.

For the ERPs we used multiple source eye correction(MSEC; Berg & Scherg, 1994). Prior to the experiment,80 calibration eye movements (vertical and horizontal)and 20 eye blinks were recorded from each participant.Using BESA (Brain Electrical Source Analysis; MegisSoftware GmbH), eye movements and blinks were aver-aged and subjected to a principal components analysis

(PCA). Then characteristic scalp topographies for arti-facts were separated from the continuous EEG.

The ERPs elicited during sentence reading by the pen-ultimate word and the sentence subject word wereanalyzed in a combined time window. For this EEG anal-

ysis, trials were averaged off-line with an epoch of200 msec before the onset of ein/kein (a/no)up to 2000 msec thereafter. To explore spatio-temporaldynamics of negation processing within the sentences,50-msec time-step analyses were performed with twotypes of ANOVAs, one including the factors negation(ein + subject noun vs. kein + subject noun) andregion (anterior vs. posterior electrode positions), the

other including the factors negation and hemisphere(left vs. right electrode positions). Electrode positions

were summarized in regions of interest (ROIs), the ante-rior and the posterior ROI both included homologueelectrode positions from both hemispheres and midlineelectrodes, together 22 electrode positions for each ROI(anterior: FP1, FP2, AF7, AF3, AF4, AF8, F5, F1, F2, F6,FT7, FC1, FC5, FC3, FC2, FC4, FC6, FT8, Fpz, AFz, Fz,FCz; posterior: TP7, CP5, CP3, CP1, CP2, CP4, CP6, TP8,P7, P1, P3, P4, P2, P8, PO9, PO1, PO2, PO10, O1, O2, Pz,

Oz). The left and right ROI both included 23 electrodeposition (without midline electrode positions) (left: FP1,AF7, AF3, F5, F1, FT7, FC1, FC5, FC3, T7, C3, C5, TP7,CP5, CP3, CP1, P7, P1, P3, PO9, PO1, TP9, O1; right: FP2

AF4, AF8, F2, F6, C4, T8, C6, FC2, FC4, FC6, FT8, CP2,CP4, CP6, TP8, P4, P2, P8, PO2, PO10, FT10, O2). Weonly report effects that reach significance in three con-

secutive time windows.For the analysis of the ERPs elicited by the picture,

trials were averaged off-line with an epoch length of1000 msec, including a prestimulus baseline from 200to 0 msec with respect to the picture onset. To clarifytemporal resolution of ERP effects in picture processing,

50-msec time-step ANOVAs were performed with therepeated measures factors delay (short vs. long), nega-tion (affirmative vs. negative), truth value (true vs. false),and region (anterior electrode leads vs. posterior elec-trode leads). For the ERPs evoked by the picture, therewere virtually no asymmetric effects. So we defined onlyan anterior and a posterior ROI as reported above. Four-

way ANOVAs with the repeated measures factors delay,negation, truth value, and region were applied to ERPanalysis. Time windows were determined with respect to

results of 50-msec analyses, as well as with respect toprevious works on language comprehension. Previously,

contextual integration of visually presented imageshas been shown to elicit N400 effects. In accordancewith other studies employing picture and word material(e.g., Federmeier & Kutas, 2001; Kutas & Federmeier,2000), a time window of 250550 msec was chosenfor the analysis of N400 effects. In some of the studiesthat presented visual images, an earlier negativity, theN300 with a somewhat more frontal distribution, has

been reported to overlap with the N400 (McPherson &Holcomb, 1999). To accomplish for possibly indepen-

dent effects of picture processing in the N400 time win-dow, we separated the analysis of the N400 into an earlytime window including a frontal N300 effect (250 msec400 msec) and a later time window including a frontalnegative shift in two conditions (short delay, true af-firmative and false negative, 400550 msec). For ERPanalysis of the post N400 time slot, a time window of 550to 1000 msec poststimulus onset was included in the

Table 2. Mean Latencies/Standard Deviations of Correct Responses (msec), and Error Percentages (in parentheses) in theSentencePicture Verification Task

Delay

Short Long

Truth Value Truth Value

True False True False

Affirmative 676/128 (1.42) 817/237 (4.88) 660/163 (3.44) 761/253 (5.17)

Negative 961/234 (10.37) 877/212 (7.05) 812/229 (6.03) 766/219 (5.34)


8/14/2019 ludtke 2008

7/16

analyses. For illustration purposes only, ERPs were low-pass filtered at 20 Hz.

RESULTS

Behavioral Data

Response Times in the Verification Task

The mean latencies, standard deviations, and the per-

centages of errors are displayed in Table 2. There was amain effect of negation [F1(1, 15) = 35.0, p < .001, F2(1,78) = 198.1, p < .001], a main effect of truth value [F1(1,15) = 4.6, p = .05, F2(1, 78) = 9.0, p < .01], and a maineffect of delay [F1(1, 15) = 52.3, p < .001, F2(1, 78) =50.9, p < .001]. As expected, there was also a Negation-by-Truth value interaction [F1(1, 15) = 22.8, p < .001,

F2(1, 78) = 80.9, p < .001] and a Negation-by-Delay in-teraction [F1(1, 15) = 27.1, p < .001, F2(1, 78) = 35.9,

p < .001], but no Delay-by-Truth value interaction (bothF < 1). The interaction of delay, truth value, and nega-

tion was also significant [F1(1, 15) = 10.3, p < .01, F2(1,78) = 4.1, p < .05].

Analyzing the data separately for the two delay con-ditions produced for the short delay a significant maineffect of negation [F1(1, 15) = 60.2, p < .001, F2(1, 39) =223.9, p < .001]. The main effect of truth value was onlysignificant in the by-item analysis [F1(1, 15) = 3.8,

p < .17, F2(1, 39) = 5.2, p < .05]. The Negation-by-Truth value interaction was significant in both analyses[F1(1, 15) = 25.6, p < .001, F2(1, 39) = 54.9, p < .001].

For the long delay there was also a significant main ef-fect of negation [F1(1, 15) = 10.8, p < .01, F2(1, 39) =29.7, p < .001] and a marginally significant main effect

of truth value [F1(1, 15) = 3.3, p < .10, F2(1, 39) =4.4, p < .05]. The Negation-by-Truth value interactionwas also highly significant in this delay condition [F1(15,1) = 16.3, p = .001, F2(39, 1) = 31.8, p < .001]. Separateanalyses for the affirmative and negative sentences inthe two delay conditions revealed for both delay con-

ditions, as expected, that responses for affirmative sen-tences were shorter in the true than in the falsecondition [for both delay conditions: F1(1, 15) > 12,

p < .01, F2(1, 39) > 44, p < .001], whereas those fornegated sentences were shorter in the false than inthe true condition [short delay: F1(1, 15) = 15.1,

p < .01, F2(1, 39) = 15.6, p < .001; long delay: F1(1,15) = 6.4, p < .05, F2(1, 39) = 2.3, p < .15]. Thus, aspredicted, responses were shorter in those conditions in which the picture was presumably primed by the sen-

tence, be it because the depicted foreground object wasmentioned in the sentence, or because the compre-hender had simulated the depicted state of affairs whenthe picture came up.

What does the three-way interaction of delay, nega-tion, and truth value reflect? Two possible explanationsarise from additional planned comparisons: First, for thefalse affirmative, the true negative, and the false negative

versions, response times in the short-delay conditionswere shorter than those in the long-delay conditions [forall comparisons: F1(1, 15) > 22.6, p < .001, t2(1, 78) >2.5, p < .02]. In contrast, for the true affirmative, there

was no difference between the delay conditions [F1(1,15) = 1.5, p > .23, t2(1.78) = 1.2, p > .20]. Second,in both delay conditions, response times were shorter

for affirmative than for negative versions [for all compar-isons: F1(1, 15) > 3.9, p < .07, F2(1, 39) > 19.8, p < .001],except for the false versions in the long-delay condition.Here, negative and affirmative conditions did not differ(both Fs < 1).

Error Percentages in the Verification Task

In the overall 2 2 2 ANOVA, there was a main effectof negation [F1(1, 15) = 12.07, p < .01, F2(1, 78) = 22.2,

p < .001] but no main effects of delay or truth value[delay: F1(1, 15) = 1.5, p > .22, F2(1, 78) = 1.1, p > .28;

truth value: bothF

< 1]. The Negation-by-Truth valueinteraction and the Negation-by-Delay interaction weresignificant [both F1(1, 15) > 10.0, p < .01, both F2(1,78) > 6.7, p < .01], but not the Delay-by-Truth valueinteraction (both F < 1). The three-way interaction wasonly marginally significant in the by-participant analy-sis [F1(1, 15) = 4.1, p < .07, F2(1, 78) = 1.6, p > .20].The separate analyses for the two delay conditions pro-duced a significant main effect of negation [F1(1, 15) =

16.6, p < .01, F2(1, 39) = 26.9, p < .001] and a sig-nificant Negation-by-Truth value interaction [F1(1, 15) =21.5, p < .001, F2(1, 39) = 9.0, p < .01] only for theshort-delay condition. No significant effects appeared in

the long-delay condition [all F1(1.15) < 2.0, p > .19,F2(1, 39) < 1.9, p > .18].

In summary, the behavioral data show the expectedNegation-by-Truth value interaction in both delay con-ditions, for latencies as well as error rates. The expected

main effect of negation was also observed, but in theerror rates it was only significant for the short delay. Astronger impact of negation for the short than for thelong delay is also indicated by the significant Negation-by-Delay interaction in the latency and error analyses. Af-firmative versions always lead to shorter response timesand lower error percentages than negative versions. How-ever, these differences were greater in the short-delay

compared to long-delay conditions.

ERPs Evoked during Sentence Reading

The first and only point at which affirmative and negativesentences differed was the presentation of the affirma-tive ein (a) and the negative kein (no). Thesubject noun followed 600 msec after the onset of ein/kein. Figure 1 shows the grand-average ERPs startingfrom ein/kein up to a second after the presentationof the subject noun for selected electrodes.

Ludtke et al. 7

8/14/2019 ludtke 2008

8/16

The presentation of ein/kein is associated with anN1P2 complex followed by a negativity and by a poste-rior positive shift that is more pronounced for negativethan for affirmative sentences starting at the P2 compo-nent. The 50-msec time-step ANOVAs with the factorsnegation and position revealed an onset of this effectat 50 msec after onset of ein/kein. The enhanced

positive shift for kein extended over the following six50 msec time windows. Accordingly, all six time windowsranging from 50 to 350 msec after onset of ein/kein

revealed a main effect of negation [for all F(1, 15) > 4.8,p < .05]. There were no interactions of negation andposition or negation and hemisphere except for the time

window ranging from 200 to 250 msec after onset ofein/kein [F(1, 15) = 5.73, p < .01]. This time win-dow only revealed an effect of the presentation of ein/kein for anterior [F(1, 15) = 8.77, p > .01] but not forposterior sites (F = 2.0).

ERPs for subject nouns during sentence reading are

also associated with an N1P2 complex followed by a widely distributed negative shift (see Figure 1). Heresubject nouns following kein elicited more negativeamplitudes than those following ein. In order to testa possible lateralization of this effect, we calculated50-msec time-step ANOVAs with the factors negationand hemisphere as described in the Methods section.This analysis revealed an onset of this negative effect at850 msec after onset of ein/kein, which is 250 msecafter the onset of the subject noun presentation. Further

examination of the negative shift using 50-msec time-step ANOVAs confirmed enhanced negativity for negatednouns in all time windows up to 2000 msec after the on-set of ein/kein, which is 1400 msec after the onsetof the subject noun presentation. Consequently, a maineffect of negation was observed in a time window rang-ing from 850 to 2000 msec after onset of ein/kein[for all F(1, 15) > 5.4, p < .05]. There were no interac-

tions of the factor negation with the factors region and/or hemisphere.

ERPs Evoked by the Picture

Figure 2 illustrates the ERPs evoked by picture presenta-tion. For better clarity, the ERPs for the four versions are

shown separately for the two delay conditions (short:Figure 2A; long: Figure 2B). Generally, all waveforms arecharacterized by an N1P2 complex followed by a broad

negativity starting about 200 msec after picture onset. Itappears as a frontal negative effect. A peak at 300 mseccan be separated from a parietal negativity with a peak at

400 msec. We will refer to the former effect as N300 andto the latter as N400. Amplitudes of both ERP deflectionsare, by virtue, equally sensitive to the experimental ma-nipulation. The N300 over frontal electrodes is followedby a negative shift between 400 and 550 msec for trueaffirmative and false negative conditions. An early time

window of the broad negativity including the N300 andthe beginning N400 effect (250400 msec) and a late time window including the negative shift and the precedingN400 (400550 msec) were analyzed to account for thenegative-going ERP effects up to 550 msec. The separa-tion of three different components in two consecutivetime windows is solved with respect to the specific topog-raphy of the frontal N300 and the negative shift on theone hand and the posterior N400 on the other hand. TheN400 was followed by a positive-going ERP component

for parietal electrode positions. A time window rangingfrom 550 to 1000 msec was applied to the analysis of thislate positivity.

N300/beginning N400 (250400 msec). The N300 andbeginning N400 ERPs for the four experimental condi-tions can be separated into two groups (cf. Figure 3A),the priming group [true affirmative (TA) and false nega-

Figure 1. Grand mean

averages related to ein/

kein (a/no) and the

following subject noun onset

for selected electrode leads.


8/14/2019 ludtke 2008

9/16

Figure 2. Grand mean

averages related to picture

onset. (A) ERPs elicited in

the short-delay conditions for

selected anterior and posterior

electrode leads. (B) ERPs

elicited in the long-delay

conditions for the same

electrode leads. Time windows

applied to analyze ERP effects

are marked.

Ludtke et al. 9

8/14/2019 ludtke 2008

10/16

tive (FN) conditions] and the nonpriming group [falseaffirmative (FA) and true negative (TN) conditions].However, as the interaction of Negation-by-Truth-value-by-Region-by-Delay proved to be significant [F(1, 15) =

4.5, p < .05], the two delay conditions were analyzedseparately.

SHORT DELAY. For the short-delay condition, the group-ing of primed and nonprimed conditions was confirmedby a significant Negation-by-Truth value interaction [F(1,15) = 28.6, p < .001] in the early time window of thebroad negativity (250400 msec).There were no maineffects of negation (F< 1) or truth value [F(1, 15) = 1.5,

p > .22] in this time window. Further analyses of the

negation and truth value effects for the different con-ditions revealed prominent effects of negation for true[F(1, 15) = 11.6, p < .01] and false conditions [F(1,15) = 20.3, p < .001] as well as effects of truth value foraffirmative [F(1, 15) = 50.3, p < .001] and negative [F(1,15) = 11.2, p < .01] conditions. For affirmative sentences,mean ERP amplitudes elicited by false versions were morenegative compared to ERP amplitudes elicited by true

versions. By contrast, for negative sentences, ERP ampli-tudes for the true versions were higher than ERP am-plitudes for the false versions. Thus, in accordance withformer studies (Hald et al., 2004; Kounios & Holcomb,

1992; Katayama et al., 1987; Fischler et al., 1983), and inaccordance with our predictions, primed conditions (TA,FN) were associated with smaller N400 amplitudes thannonprimed conditions (FA, TN). When contrasting primedconditions (TA, FN) or nonprimed conditions (FA, TN),no significant ERP effect was found for this time window(all: F < 1).

LONG DELAY. For the long-delay condition, the powerfulpriming effect on ERPs is also prominent as revealed

by a significant Negation-by-Truth value interaction [F(1,15) = 17.2, p < .001], but here it is supplemented by aneffect of negation as confirmed by a Negation-by-Regioninteraction [F(1, 15) = 9.4, p < .01]. Follow-up compar-isons revealed effects of truth value for negative [F(1,15) = 15.1, p < .001] and affirmative conditions [F(1,15) = 5.2, p < .05] as well as an effect of negation fortrue conditions [F(1, 15) = 11.0, p < .01]. For false

Figure 3. Difference waves

and scalp topographies.

(A) The negation by truth

value interaction. Effects were

found for the N400 component

in both delay conditions,

and for the negative shift in

the short-delay conditions.

(B) Main effects of negation,

which were found for the late

positivity in the short-delay

conditions and for the N400

in the long-delay conditions.

(C) Main effects of truth value,

which were only found in the

N400 for long-delay conditions.

FPO


8/14/2019 ludtke 2008

11/16

conditions, only a marginal effect of negation was ob-served [F(1, 15) = 3.2, p = .09]. In addition, a maineffect of negation was observed for anterior [F(1, 15) =6.0, p < .05] as well as posterior regions [F(1, 15) =

13.5, p < .01].

Late N400 time window/negative shift (400550 msec).

A Negation-by-Truth-value-by-Region-by-Delay interaction[F(1, 15) = 5.6, p < .01] points to differences in the de-

lay conditions regarding effects on amplitudes elicited be-tween 400 and 550 msec.

SHORT DELAY. In the short-delay condition, an interactionof negation, truth value, and region was significant [F(1,15) = 10.9, p < .01]. For both regions, the Truth-value-by-Negation interaction was significant [posterior sites:

F(1, 15) = 5.91, p < .01; anterior sites: F(1, 15) = 9.50,p < .01]. At posterior sites, the conditions with priming

(TA and FN) differed from those without priming (FAand TN) by a reduced negativity as in the early N400

time window [for all F(1, 15) > 11.6, p < .05]. Incontrast, at anterior sites, the conditions with priming(TA and FN) led to enhanced negativity compared tothose without priming (FA and TN). For affirmative sen-tences, true versions resulted in a larger amplitude thanfalse versions [F(1, 15) = 5.2, p < .05], but for nega-tive sentences, false versions resulted in a larger ampli-

tude than true versions [F(1, 15) = 9.8, p < .01]. TheNegation-by-Truth value interaction separates ERPs foranterior and posterior electrodes in the late N400 time

window. Only the posterior deflection is equivalent tothe classical N400 effect observed in previous ERP stud-ies, whereas the anterior sites show a reversed pattern.

LONG DELAY. For long-delay conditions, no Negation-by-Truth value interaction was found [Negation Truthvalue: F(1, 15) < 1; Negation Truth value Region:F(1, 15) = 1]. The separation of primed and nonprimedconditions that shaped the early N400 window for both

delay conditions as well as the later time window for theshort delay can no longer be detected for the long-delayconditions. Instead, Negation-by-Region [F(1, 15) = 7.2,

p < .05] and Truth-value-by-region [F(1, 15) = 16.5, p

Documents

ludtke 2008