Abstract ADHD is a psychiatric disorder characterised by persistent and develop-mentally inappropriate levels of inattention, impulsivity and hyperactivity. It is knownthat children with ADHD tend to produce incoherent discourses, e.g. by narratingevents out of sequence. Here the aetiology of ADHD becomes of interest. One prom-inent theory is that ADHD is an executive function disorder, showing deficiencies ofplanning. Given the close link between planning, verb tense and discourse coherencepostulated in van Lambalgen and Hamm (The proper treatment of events, 2004), wepredicted specific deviations in the verb tenses produced by children with ADHD.Here we report on an experiment corroborating these predictions.
In a pioneering study, Trabasso and Stein (1994) have argued that discourse produc-tion, for instance in a narrative task, requires a form of planning. In van Lambalgen andHamm (2004), van Lambalgen and Hamm have shown how some of the mechanismswith which discourse coherence can be achieved—tense, aspect, adverbials—can also
This article is based on the theoretical analysis of executive function given by Stenning and vanLambalgen (2007). The analysis of the narratives of the children with ADHD is due to the second andthird authors. The application to tense processing owes much to conversations with Giosue Baggio.
M. van Lambalgen (B) · C. van KruistumInstitute for Logic, Language and Computation, University of Amsterdem, Nieuwe Doelenstraat 15,1012CP Amsterdam, The Netherlandse-mail: [email protected]
E. PariggerAmsterdam Centre for Language and Communication,University of Amsterdam, Spuistraat 210, 1012VT Amsterdam,The Netherlands
123
468 Michiel van Lambalgen et al.
be viewed as instances of planning. It is therefore interesting to pursue the hypothesisthat developmental orders in which planning is known to be compromised lead todeviant forms of discourse production. For this purpose it turns out to be useful toconsider planning in the wider context of executive function and its disorders.
‘Executive function’ is an umbrella term for processes responsible for higher-levelaction monitoring and control that are necessary for maintaining a goal, and achievingit in possibly adverse circumstances. Several psychiatric disorders are accompaniedby what seems to be executive dysfunction, and in fact executive failures have beenhypothesised to cause these disorders. For instance, in ADHD one can observe diffi-culties with response inhibition, vigilance, working memory and planning (for a recentoverview see Willcutt et al. (2005)), and it is tempting to suppose that these problemsare the cause of the behavioural problems associated with ADHD. The problem withsuch hypotheses is that executive function is not a very well-defined concept (andneither is ADHD, for that matter). The concept of executive function originated fromneuropsychological study of patients with impairments in this area, and the field stillsuffers from lack of a comprehensive positive characterisation of just what executivefunction is. There is also no unanimity on how to partition executive function intomeaningful sub-components. This is unfortunate if one’s aim is to try to view dif-ferent psychiatric disorders as caused by failures in different sets of components ofexecutive function, thus moving beyond the general statement that executive functionis compromised in psychiatric disorders.
In Stenning and van Lambalgen (2007) it is argued that logical modelling is usefulin providing executive function with conceptual coherence. It is also shown that log-ical modelling leads to testable predictions in the behavioural domain. The exampleconsidered there is autism; the prediction is that autists behave very differently fromnormals in the so-called ‘suppression task’, a reasoning task which requires the abilityto withdraw an earlier conclusion in the light of new information. In the meantimethis prediction has been verified (Pijnacker et al. 2007).
In the present paper we apply the approach to ADHD, viewed tentatively as exec-utive dysfunction. We take our cue from data showing that narratives of children withADHD exhibit (i) retelling of story events out of sequence, and (ii) ambiguous ana-phoric references to events (Purvis and Tannock 1997). This indicates that in thesechildren temporal semantics is compromised. In van Lambalgen and Hamm (2004) itwas shown that temporal semantics can be viewed as mediated by the human planningsystem, hence by executive function, and from this we derive predictions concerningthe use of tense, aspect and temporal adverbials in narratives produced by childrenwith ADHD. The predictions have been tested by the second author and the resultsare reported here.
1 A Logical Description of Executive Function
Taking executive function to be composed of planning, initiation, inhibition, mon-itoring, co-ordination and control of action sequences, leading toward a goal heldin working memory, Stenning and van Lambalgen (2007) claimed that the oper-ation of executive function can be described as a form of conditional reasoning,
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 469
and aberrations thereof. The authors identified closed world reasoning as a centralcomponent—corresponding to inhibition—of the logical description of executivefunction, and showed, both theoretically and experimentally, that executive dysfunc-tion can be viewed as a failure in closed world reasoning. It may seem paradoxical thata largely automatic process such as executive function is associated with reasoning,which seems to involve conscious deliberation. But it is the association of reasoningwith conscious deliberation that is wrong: whether or not reasoning needs conscious-ness depends very much on the computational complexity of the type of reasoningthat the reasoner engages in. Classical reasoning is notoriously complex, but closedworld reasoning is not.
For our present purposes—relating planning to temporal semantics and deviant useof tense—we need not go deeply into closed world reasoning, but we must say some-thing about the formal analogues of planning and working memory, and the role ofgoals therein.
Planning consists in the construction of a sequence of actions which will achieve agiven goal, taking into account properties of the world and the agent, and also eventsthat might occur in the world. The relevant properties include stable causal relation-ships obtaining in the world, which can be formulated as suitable conditionals. Toexpress these relationships in a fully precise manner one needs a formalism such asthe event calculus (see for instance van Lambalgen and Hamm (2004), but for purposesof exposition we use propositional logic here. When we come to deviations of verbtenses in ADHD we will use a richer formalism.
From a logical perspective, planning can be viewed as an instance of logic pro-gramming.1 A logic program is a finite database of conditionals of the form ϕ → q,where q is atomic. A goal is a finite list of literals,2 written ?L1, . . . , Ln . In the contextof planning, the goal represents a description of the desired state. The purpose of thecomputation is to determine what conditions must be met to satisfy the goal, usingonly the conditionals in the database. A computation starting from a query ?A with adatabase containing the conditionals B1, . . . , Bn → A and C1, . . . , Cm → Bi can bepictured as a tree as in Fig. 1. If the computation ends with the empty goal, this meansthat the original goal can be satisfied. If the computation terminates, but the last goal isnon-empty, this means that the database must be updated with literals in the last goalin order to make the original goal satisfiable. In the case of planning these updateswill consist of reports that the actions leading toward the goal have been executed.3
We view the maintenance of the goal stack—the currently active goal together withthe goals from which it was derived—as as a function of working memory. Planningitself involves more, in particular search for relevant conditionals in declarative mem-ory, and unification of the currently active goal with the consequent of the conditionalselected.
1 The classical reference is Kowalski (1979); a modern exposition can be found in Doets (1994).2 A literal is either an atom or the negation of an atom.3 The above description of a computation in logic programming uses goals as integrity constraints, asdeveloped by Kowalski (1995). The application of integrity constraints to verb tenses used in the nextsection is developed in van Lambalgen and Hamm (2004), Chap. 8.
123
470 Michiel van Lambalgen et al.
Fig. 1 An example of a computation
2 Verb Tenses from Planning
We now connect the preceding abstract considerations to the domain we are interestedin, verb tenses. In the book The proper treatment of events (van Lambalgen and Hamm2004) the main function of tense and aspect is considered to be the construction ofevent structures from discourses. This construction is viewed as a planning problem:the same mechanism which in planning constructs a sequence of actions is responsiblefor the construction of event structures from discourses. In this set-up, verb tenses arerepresented as goals in the same sense as goals are used in planning.
More precisely, the task of the speaker is to formulate a goal (by means of a sen-tence in natural language) which allows the hearer to update his or her event structure(‘discourse model’) with the new event expressed by the sentence. The event struc-ture comprises a (partial) order of the events in terms of relations such as ‘precedes’and ‘overlaps’, and rudimentary indications of the durations of, and spacing betweenevents. Ideally, such a goal has two components:
(1) location of the event in past, present or future(2) meshing the event with events introduced previously
Thus, the computational function of verb tenses is much more than locating an eventwith respect to now; the real computational burden is borne by the incorporation of theevent in the discourse. For our purposes, the interesting question is how this burdenis divided over speaker and hearer. A ‘pragmatically sensitive’ or ‘emphatic’ speakerwill formulate the goal in such a way that the computational burden on the heareris minimal. By contrast, a speaker with no concern for the hearer, may leave out thecontextual information that would facilitate the hearer’s computations.
An example will make this clearer. Suppose a speaker wants to convey the messagethat John pushed Max, and that as a consequence Max fell. One way to do this is viathe mini-discourse
Max fell. John pushed him.
Note that here the order of the sentences is the reverse of the order of events. The goalsconveyed by this discourse are
(1) ‘update discourse with past event e1 = fell(m) and fit e1 incontext’
(2) ‘update discourse with past event e2 = push(j,m) and fit e2in context’
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 471
The first part of these goals can be executed immediately; one does not have toconsider a reduction to other goals. It is the fitting into the context that is compu-tationally costly; why this is so can be seen if the condition ‘fit e2 in context’is spelled out. For a start, the general form of the condition must be something like
(1) fit e2 in context {e, e′, e′′, . . .}, where {e, e′, e′′, . . .} is a set ofvariables for events.
These variables have to be unified with the events activated in the given context, whichwill come with an event ordering expressible in terms of < (‘precedes’).4 The instruc-tion ‘fit’ then asks for an extension of this ordering with e2. In the case at hand, thegeneral condition reduces to ‘fit e2 in context {e1}’, and the instruction ‘fit’can be viewed as asking which if any of the queries ?e1 < e2 and ?e2 < e1 can be madeto succeed. It is hypothesised here that it is the planning system which determines theevent structure from the discourse. In order to do so, the planning system recruitscausal knowledge as well as the principle that causes precede effects. Applied to thecase at hand, the planning system scans declarative memory for causal connectionsbetween e1 and e2 and finds (roughly) ‘e2 is a cause of e1’. This fixes the temporalorder of e1 and e2, with e2 preceding e1.5
Viewed in this manner, the computation for the hearer involves
(1) keeping the context active in working memory, that is, events and their order(2) search and unification prompted by the ‘fitting’ condition(3) execute in parallel the backtracking derivations that determine the place of the
new event with respect to the old event order(4) this step in itself involves a search for applicable causal information, and unifica-
tion
This computation is more complex than the simple location of the event in past, present,or future, which can be read off immediately from the verb tense.
If the preceding is a good, albeit high-level, description of the computations involvedin producing and comprehending verb tenses, we can identify factors which affect thecomputational load for speaker and/or hearer.
(i) The speaker must produce a goal that is satisfiable, so that the hearer can start asuccessful computation from the given goal. An example6 where this is not thecase is(2) Hij viel bovenop het gewei. Het hert is kwaad en liep naar de afgrond.
He fell onto the antlers. The deer is angry and walked to the ravine. [9yrs,ADHD]
4 The event order need not be total; indeed it may be the function of the sentence under consideration tofill in missing bits.5 Inferring this event order is a defeasible process; if the discourse had continued beyond ‘him’, as in
Max fell. John pushed him, or rather what was left of him, over the edge.
the order of e1 and e2 is now different, since it conjures up a scenario like the following: John does some-thing particularly nasty and bloody to Max which makes him fall, near the edge of precipice; he then shovesthe body over the edge of the precipice: thus e1 precedes e2.6 Taken from the experiment reported in Sect. 4. The utterances are labelled with the age of the child andthe group to which it belongs, ADHD or C(ontrol)G(roup).
123
472 Michiel van Lambalgen et al.
The past tensed ‘walked’ is incongruous after the present tensed ‘is’. The past tensetakes its reference point (which must lie in the past) from the context, but the firstconjunct has identified that reference point with the utterance time.7 Note that thetransition from ‘fell’ in the first sentence to ‘is’ in the second can still be interpreted(with some effort) as a transition to the narrative present, which formally means makingthe ‘now’ representing utterance time a variable that can be unified with the precedingreference point. No such reinterpretation is possible however for the transition from‘is’ to ‘walked’ within the second sentence.
It is then an interesting question what is entailed by the requirement that the speakerformulates a satisfiable goal. One may at first be tempted to think this is a matterof morpho-syntax only, not semantics. But a uniform morpho-syntactic consistencyrequirement like ‘use the same tense through the whole discourse’ quickly falls foulof more creative language use such as the narrative present. This means that the con-sistency requirement must be of a semantic nature, so that the speaker must in essenceperform the same computation as the hearer in order to see whether the goal he is in theprocess of formulating is satisfiable. As a consequence, the speaker can ease his owncomputational burden by omitting the satisfiability check, or by leaving out tense inindicative sentences at all, so that, if the model of (Van Lambalgen and Hamm 2004)is correct, there is no goal whose satisfiability is to be checked in the first place. As weshall see in greater detail later, some children with ADHD indeed adopt this strategy,by producing utterances without any verb8, or by resorting to direct speech.9
(ii) The speaker eases the computational burden of the hearer if the goal (i.e. thesentence produced) contains sufficiently many context setting elements. Forupon hearing a particular tense form, say a past tense, the hearer activates agoal of the form (1), and he has to unify the variables in the goal with con-textual material. If these are provided by the speaker, this eliminates a searchstep. Context-setting can be achieved by temporal adverbials, or by connectingclauses such as ‘when’, ‘and then’, ‘because’ or ‘but’. The following examplesillustrate the contrast.
(3) a. Max fell. John pushed him.b. Max fell because John pushed him.
A defining condition for ‘e1 because e2’ is that e2 precedes e1, so that the computationof the event order in the second sentence is trivial as compared to that for the firstsentence.
7 Thus there is no unification which makes this goal satisfiable. This impossibility of unification leavesinteresting traces in the EEG. See Baggio (to appear) for discussion.8 E.g.,
9 That is, by reporting what they imagine the protagonists to have said. Direct speech can take the form ofindicatives, of questions or of imperatives. The tenses of the verbs in direct speech, even in indicatives, donot contribute to the construction of the discourse model, so do not need a consistency check.
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 473
(iii) The choice of tense also influences the complexity of production andcomprehension of the goal. In a narrative task, a speaker not usingdirect speech has a choice between past tense and present tense, wherethe latter must be understood as narrative present. In the present tense,utterance time, reference time and event time coincide. Therefore in thereal use of the present tense no context-setting elements are necessary. Thisis different if the interpretation is that of a narrative present. Here are twoexamples from Google:
(4) a. So, on Tuesday I arrive at work and my laptop fails to start up. Itpowers on and then shuts down 2–3 seconds later.
b. I caught a train early from Frankfurt to get to Kassel in timefor a press conference on Tuesday. I arrive well on time. Every-thing is much slower here, I am glad, I need to pace myself alittle.
In (4-a), the adverbial ‘on Tuesday’ must refer to a past Tuesday, and still the mainclause uses the present tense. In (4-b) the context is set by an event which is explicitlyin the past, but nonetheless the remaining sentences of this discourse are in the pres-ent tense. This means that the ‘now’ of the present tense in its narrative use actuallybecomes a variable that must be unified with already established reference points; it isno longer a constant with fixed reference. If the goal provided by the speaker does notinclude reference points to which ‘now’ can be anchored, the computational burden onthe hearer is increased. Thus, a sequence of clauses in present tense without temporaladverbials or other context-setting elements may need considerable computation onthe part of the hearer to determine the ‘spacing’ of events.
3 ADHD, Executive Function and the Art of Telling a Story
ADHD is characterised by persistent and developmentally inappropriate levels ofinattention, impulsivity and hyperactivity, and about 2% of children (mainly boys)are severely affected; 3–6% suffer from less severe symptoms.10 It has been hypoth-esised to be an executive function disorder, and indeed children with ADHD scoresignificantly lower on a number of standard tests measuring components of execu-tive function, such as planning, inhibition, and self-monitoring. The precise patternof executive deficits in ADHD is not yet known, and it is not yet determined whetherthere is a single executive deficit that explains most of the symptoms. Below wewill investigate consequences of the hypothesis that goal maintenance is affected inADHD, evidence for which can be found in Shue and Douglas (1992), Penningtonand Ozonoff (1996). We will be particularly interested in the effect of deficient goalmaintenance on language processing, and we therefore briefly introduce some of therelevant neuropsychological data.
10 These are figures for the Netherlands, supplied by the Gezondheidsraad.
123
474 Michiel van Lambalgen et al.
3.1 Executive Deficits in ADHD
Shue and Douglas (1992) have shown that children with ADHD score significantlyworse than neurotypical subjects on a family of tasks which involve synthesis andexecution of a plan achieving a given goal. The paradigm case is the ‘Go/NoGo’ taskwhose basic structure is as follows: on one type of stimulus the subject has to pressa key (this is the ‘go’ stimulus), on another type of stimulus the subject must not doanything (the ‘no go’ stimulus). Stimuli are presented in random order. In the ver-sion of Shue and Douglas (1992), the ‘go’ stimulus is a card showing an apple, andthe ‘no go’ stimulus a card showing an ice cream;11 the response is pressing a key.Viewed as a (rather minimal) planning problem the computation goes like this. Thegoal is ‘do(x) now’, with x a variable to be instantiated. There are two rules, whichcan be formalised as ‘if apple, do(go)’ and ‘if ice cream, do(no go)’. This meansthere are two possible unifications for the variable x in the given goal, the actionsgo and no go, which reduce the goal to satisfying one of the preconditions, appleor ice cream. The (unique) successful unification then determines the action to beperformed.
The plan P synthesised by this computation is of the form IF C1 THEN A1 & IF C2THEN ¬A1 Of course if all goes well, after a few trials performance is determined bythe automatically executed plan P (which proceeds forwards from stimulus to action),and not by the explicit computation of this plan (which proceeds backwards fromgoal to stimulus). But performance on this task in children with ADHD is signifi-cantly impaired in that many ‘no go’ trials lead to a ‘go’ response, and this suggeststhat the initial computation (unification and reduction of the goal ‘do(x) now’) is notexecuted correctly.12 If the ‘go’ response is conceived as an unconditional response,that is, if the goal is simplified to ‘do(go)’, it does not require any computation. Wethus view the performance of children with ADHD on these tasks as evidence for thedifficulty of keeping a complex goal active in working memory, and the tendency tosimplify that goal as a consequence. It is this interpretation13 that we shall apply tothe analysis of discourse production, in particular verb tenses, below. The link from‘Go/NoGo’ tasks to verb tenses is provided by the analysis of verb tenses in termsof complex goals maintained in working memory, as explained in Sect. 2. Indeed, theapparently problematic ingredients in the ‘Go/NoGo’ task: maintaining the goal, uni-fication and then reduction of the goal, are very prominent in the computation of verbtenses.
11 There are 20 cards for each of the ‘go’ and ‘no go’ stimuli, so it is not a matter of building up a responsebias.12 Unfortunately, it is not reported in Shue and Douglas (1992) whether there are symmetrical errors withthe ‘go’ trials.13 We are aware that the results on the Go/NoGo task are often interpreted as evidence of a failure inresponse inhibition. However, such a gloss on the results makes it difficult to understand why autists,known to have difficulty with ‘inhibiting the prepotent response’ (Russell 2002), do well on this particularGo/NoGo task (Ozonoff et al. 1994). This interpretational difficulty shows, if nothing else, how importantit is to come up with precise formal analyses of the tasks involved.
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 475
Fig. 2 Pictures 1–3 from “Frog, where are you?”
3.2 Discourse Production in ADHD
Language ability also seems to be affected in ADHD, in particular with regard tosemantics and pragmatics. This has been investigated using story telling tasks, in twoforms. In Purvis and Tannock (1997) a folk tale ‘The father, his son and their donkey’was read to the children, who then had to repeat the story. In Blankenstijn and Scheper(2003) the ‘Frog story’ paradigm was used, in which children were asked to narratea sequence of 24 scenes in a picture storybook called Frog, where are you? (Mayer1969), where a boy attempts to find his pet frog that has escaped from its jar. This isa classic experimental paradigm for investigating the acquisition of temporal notionsin children. See Berman and Slobin (1994) for methods, results, and last but not least,the frog pictures themselves; the opening scenes are given in Fig. 2. The drawingsdepict various failed search attempts, until the boy finds his frog by accident. Thepurpose of the experiment is to investigate what linguistic devices, in particular tem-poral expressions, children use to narrate the story, as a function of age and mentalcondition.
The narrative tasks in Purvis and Tannock (1997) and Russell (2002) both seemto involve executive function, in particular planning and goal maintenance. One gen-eral connection between narration and planning has been illuminated in Trabasso andStein (1994), whose title says it all: “Using goal-plan knowledge to merge the past
123
476 Michiel van Lambalgen et al.
with the present and future in narrating events on line”. The main idea is that theevents depicted in the book are naturally structured in time as a sequence of actionsaimed toward achieving a goal, and hence the narration is like the unfolding of a plan.Executive difficulties are therefore likely to result in deviant narration patterns, andindeed several such have been observed. For instance Purvis and Tannock (Purvis andTannock, 1997, pp. 136) observed a tendency to retell story events out of sequence;this reflects a breakdown in overall goal–plan organisation. Another phenomenon thatthese authors noticed, ambiguous anaphoric references to events, will be of specialinterest of us, since it reflects a more local breakdown of planning, a failure to achievediscourse cohesion. In particular we will see that children with ADHD have variousdifficulties with using verb tenses, thus causing breakdown of discourse cohesion.
3.3 Deviant verb Tenses and ADHD
We are now in a position to formulate hypotheses on the the production and compre-hension of verb tenses in narrative tasks by children with ADHD.
For production one would generally expect decreased coherence of the narrativeproduced. That is, a speaker with ADHD will attempt to simplify the goal conveyedby his utterance even if that means increasing the processing load of the hearer. Basedon a coarser form of the analysis given in Sect. 2, Stenning and van Lambalgen (2007)gave the following list of phenomena they expected to see.
3.3.1 Anchoring
To simplify a goal, the child with ADHD may be tempted to omit temporal anchorswhere they are obligatory, as in the simple past tense (Steedman, 1997, pp. 906). Outof the blue a sentence like (5-a) is infelicitous, but with a temporal adverbial or asubordinate clause, felicity is restored, as in (5-b).
(5) a. �It rained.b. Yesterday/When I stepped outside, it rained.
Now suppose the speaker is a child with ADHD. Producing a sentence like (5-b)requires the explicit integration of context and main event.14 If in the mind of the childwith ADHD the goal corresponding to the past tense is simplified by dropping themeshing part, this should show as an increased production of ‘bare’ past tenses as in(5-a).
3.3.2 Perfect Tenses
A more subtle deviation is predicted to occur with the production of perfect tenses.Generally, the goal corresponding to a perfect tense has the following structure
(1) locate the event in the past of the reference time
14 See for example (van Lambalgen and Hamm, 2004, pp. 112–114) for a discussion of when clauses whichestablishes this point.
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 477
(2) the reference time is situated in the state resulting from the event(3) for the past perfect, the reference time must be determined by context
Unlike the case of the past tense, here the first instruction cannot be executed withoutthe unification demanded by the third instruction. This is definitely a problem in thecase of the past perfect, since there the reference time is earlier than the utterancetime. The problem also occurs for the present perfect when it is used in the contextof the narrative present, since the story—‘now’ is different from the utterance time.Furthermore, the use of a perfect tense in an utterance constrains the use of a simpletense in the next utterance, since the event must be located at the reference time givenby the perfect. The use of the perfects requires some foresight and planning as well asintegration with preceding material.
Here is an example of what can go wrong. A scene in the beginning of the ‘Frogstory’ (Fig. 2) could be described thus
(6) Toen ging het jongetje slapen. En toen wou de kikker eruit. Want hij had er geendop op gedaan.Then the boy went to sleep. And then the frog wanted to get out. Because hehadn’t put a cap on [the jar]. [8yrs, CG]
but also as
(7) Een jongetje had een kikker gevangen of, ja. En hij heeft d’r in een potje gedaan.En toen ’s avonds liep de kikker eruit. En toen was het dag. En toen werd hetkind wakker.A boy had caught a frog, or something like that, yes. And he has put her in a jar.And then at night the frog walked out. And then daytime came. And the childwoke up. [9yrs, ADHD]
The use of the past perfect in (6) is fine: the state resulting from not putting a cap onthe jar is thereby shown to hold at the time of the frog’s escape. The use of the presentperfect in the second sentence of (7) is infelicitous in combination with the simplepast tense of the third sentence. The dominant tense of this passage is the past tense,and the use of the present perfect leads to inconsistency.
We expected significantly fewer correct uses of the perfect tenses in children withADHD. The present population (cf. Sect. 4) with children aged 7–9, is not ideal fortesting this prediction however, since also normal nine-year olds use the perfects muchless than adults.
3.3.3 General form of the Predictions
The most general prediction that follows from the analysis given in Sect. 2is:
(8) A speaker with ADHD simplifies the goals corresponding to tenses at theexpense of the hearer.
We list here a number of ways in which these goals can be simplified. An extreme formof simplification is not to use tensed verbs at all. As explained in footnote 9, anotherform of simplification is to use direct speech, with or without tensed verbs. Togetherwith the complexity-reducing strategies given in Sects. 3.3.1 and 3.3.2, this gives us
123
478 Michiel van Lambalgen et al.
at least four strategies. The theory identifies other strategies as well: one would forinstance expect fewer utterances in which several events are connected. The prediction(8) should then lead to the following observable consequence
(9) Children with ADHD use a complexity-reducing strategy significantly moreoften than control children.
4 A Narrative Study
4.1 Subjects
In the choice of subjects, age is the determining factor. Deviations are more likely toshow at an age where the expression of temporality is still in development. Fortunately,we have the results of Berman and Slobin (1994) to build upon. They found that chil-dren as young as 3–4 years of age are able to produce pieces of discourse which areboth intelligible and relevant to the task at hand (Berman and Slobin, 1994, pp. 42).However,
[t]he ability to produce extended narratives which are well-formed in terms ofhierarchical thematic structuring and global organisation emerges relatively late,well beyond the period when children produce sentences which are syntacticallyimpeccable (Berman and Slobin 1994, pp. 42–43).
As against this early emergence of structural proficiency, there are some formsin each language which do not occur at all in the texts of the younger children,being confined to occasional appearances among the 9-year-olds, or to strictlyadult usage (Berman and Slobin 1994, pp. 599).
At 3, 4 or 5 years of age, children still have a long way to go, even though their textsshow clear signs of temporal organisation (Berman and Slobin, 1994, pp. 55). Thepast perfect (‘had read’, ‘had given’) is an example Berman and Slobin give of a formthat is acquired relatively late (Berman and Slobin, 1994, pp. 599). In addition, onlyin the narrations of the 9-year-olds explicit reference is made to causal and not merelytemporally sequential connections between series of events (Berman and Slobin, 1994,pp. 70), and even then this happens only occasionally. Their narratives still are far frommature, but a significant development seems to take place across the 5–9 age range.For practical reasons we had to restrict ourselves to the age range 7–9. This meansthat there is much room for improvement of the present study by extending the agerange on both sides. As will be seen below, some of the phenomena we are interestedin are only present in rudimentary form in normal 9 year olds.
The group of children with ADHD comprised 26 subjects, the control group 34subjects.15 The children with ADHD all fell in the so-called ‘combined type’ cate-gory, meaning they have both attention and hyperactivity problems. The breakdownaccording to age group is given in Table 1. An awkward feature of our ADHD popula-tion is the presence of comorbidity: 22 out of 26 children have other disorders as well.
15 The transcripts come from three sources: Roelofs (1998), van der Meulen (2003) en Aarssen (1996).
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 479
Table 1 Number of subjects indifferent age groups
Age (years) Control group (Boys) ADHD group (Boys)
Usually, the child shows one other disorder in addition to the primary one (38.5%),but there one can also find two (11.5%), three (26.9%) or even more non-primarydisorders. Examples of such disorders are behavioural disorders (16.6% of all comor-bid disorders), anxiety disorders (39.6%) and not being toilet trained (25%). Thesefigures unfortunately make it unlikely that all children in the ADHD group have thesame executive function profile.
Almost all ADHD children used medication (92.3%), mostly Ritalin. However, thechildren discontinued their use of Ritalin prior to the day of testing, and due to itsshort decay time the medication could not influence performance.
4.2 Materials
The children narrated the storybook Frog, where are you? (Mayer 1969), consistingof 24 pictures. They were allowed to go through the book first. They then narratedthe story to go with the pictures while leafing through the book again. The researchercould not see the pictures and emphasised: I dont know the story, it is your story.ÓNote that in the study of Berman and Slobin, the story was always told to a listenerwho already knew the story and was able to see the pictures. They therefore consideredit likely that this situation heightened the tendency of young children to engage in agood deal of pointing Ð both in gesture and in the use of deictic expressions (Bermanand Slobin, 1994, pp. 24). When they devised a new procedure aimed at overcomingthe problem of shared knowledge and perception, they found a considerable reduc-tion in deixis, both to protagonists (‘this one) and to pictured locations and situation(‘here) (Berman and Slobin, 1994, pp. 25). The experimental set-up may therefore beassumed to make the tendency for children to rely on deixis less likely.
The children’s narratives were recorded with video and audio and then transcribedand coded for relevant features. In the interest of space we omit details of the tran-scription process, but these details are available from the authors upon request.
4.3 Results
In the justification of their methodological set-up, Berman and Slobin admitted thatquantitative analyses proved inadequate in the context of the functionally orientedthrust of their study:
[…] when we started to evaluate use of tense and aspect in our transcripts,it became evident that the quantitative distribution of these forms needed tobe evaluated in terms of how they function within a given text, in relation to
123
480 Michiel van Lambalgen et al.
such factors as overall-tense selected for a particular narrative, and where tenseand/or aspectual markings were changed across that text (Berman and Slobin,1994, pp. 24).
In other words, ideally each form is to be analysed within the discourse context. Thedownside to such a qualitative method is that the numbers (of both subjects and forms)often become too small to perform statistical tests. When groups are further dividedaccording to dominant tense used or using a particular form at all, the numbers becomeeven smaller. For instance, above (in Sect. 3.3.2) we have explained why it makes senseto look at the present perfect (e.g. ‘have looked’) and past perfect (e.g. ‘had looked’).However, the perfect forms make up only 5.1% of the total number of tenses used byboth the ADHD and the control group. When we further divide the perfect accordingto the function the form fulfils within discourse, the numbers become smaller andsmaller.
Nevertheless, the main hypothesis, (9) above, is corroborated: in their narratives,children with ADHD use a complexity-reducing strategy significantly more often thancontrols (p < 0.000). We will give the data in Sect. 4.3.6, but in order to understandthe figures given there, it is useful to first study the specific strategies in detail.
4.3.1 Direct Speech
Children with ADHD do indeed tend to use more quotes in their narratives. Here aretwo ways of narrating the same scene: the boy climbs into a tree and looks into a hole,whereupon an owl appears in the hole.
(10) a. En die jongen ging zoeken in de boom. En toen zag die een uil. En toenvalt ’ie van de boom.And that boy started looking in the tree. And then he saw an owl. And thenhe falls from the tree. [8yrs, CG]16
b. “Oh nee, ik val!” “Hellup!” “Ga weg, stomme uil, ga weg!”“Oh no, I’m falling!” “Help!” “Go away, stupid owl, go away!” [9yrs,ADHD]
We have seen in Sect. 2 that there are definite computational advantages (for thespeaker) to using direct speech, and we find indeed that children with ADHD tendto economise in this way (see Table 2). As we can see from Tables 2 and 4 out of 26children from the ADHD group use direct speech in more than 12% of their utter-ances, where 12% is the mean use of utterances in direct speech per child, plus onestandard deviation. This difference is statistically near-significant (p = 0.065).17 InSect. 4.3.6 we shall see that it is advantageous to view such above-average use as astrategy. By combining several such strategies we will be able to construct a highlysignificant difference between the ADHD and control groups.
16 The child makes a mistake in combining present tense ‘valt’, which could be interpreted as a narrativepresent heightening the tension, with the adverbial ‘en toen’, which needs a past tense.17 In the presentation of results, all significance levels are relative to the (non-parametric) Mann-Whitneytest.
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 481
Table 2 Use of direct speechPercentage of Control group (%) ADHD group (%)utterances in DS (%)
As we observed in Sect. 2 the most drastic way to simplify the goals corresponding totense is to leave out these goals altogether. Much to our surprise, a considerable num-ber of the ADHD children indeed resort to this strategy, also outside direct speech. Forexample, only 2.9% of the control children used tenseless utterances (outside directspeech) at least 3 times, whereas 19.2% of the ADHD children did so. Overall, the dif-ference between control children and children with ADHD has p-value 0.081, whichis striking in view of the small number (66) of tenseless utterances. Here is an exampleof this phenomenon:
(11) En hij is vroeg op. En wat ziet die daar? Kikker verdwenen.And he is up early. And what does he see there? Frog gone. [7yrs, ADHD]
The last clause contains a past participle but no tensed verb, and therefore does notrequire processing of a goal.
4.3.3 Tense Shifts Leading to Incoherence
Let us start with an example of discourse incoherence due to a tense shift:
(12) Toen waren ze wakker. Toen zagen ze geen kikker meer. Kijkt ie in zijn laars.Toen roepte die.Then they were awake. Then they didnot see a frog anymore. He looks in hisboot. Then he called. [7yrs, ADHD]
This is incoherent because the event ‘he-look-in-his-boot’ is anchored to utterancetime, not to the events described in the preceding and following sentences. Thus thehearer must engage in a recomputation, perhaps re-interpreting ‘He looks in his boot.’as ‘On this picture, he looks in his boot.’ We expected the children with ADHD toemploy such erratic tense shifts much more often. Indeed, we do find such a trend,but the difference does not reach significance. The results are given in Table 3, whichshows the number and the percentage of children who commit 0, 1–3, or more than 3erroneous tense shifts.
4.3.4 Anchoring and Connectivity
Berman and Slobin have studied in great detail the development of the linguisticdevices used to link events to specific times or to other events. They write(Berman and Slobin, 1994, pp. 173): “Here we are concerned with the way speak-ers link parts of their narrations to construct a unified, organised piece of text.” They
found (Berman and Slobin, 1994, pp. 186) that “the 5- and 9-year-old English narrators[…] rely heavily on ‘and then’ as a means for chaining one clause after another innarrative sequence. Only adults use a variety of linking devices […] .” The narra-tions of their 5- and 9-year-olds are still strongly additive in character (i.e., using ‘andthen’), whereas the adults “stack connectivity devices across chunks of clauses, creat-ing longer stretches of event packaging than noted among children (ibidem, pp. 180)”.Examples include anchoring adverbials like ‘in the morning’. Such examples areused to show that "mature narrators can organise their texts from a thematically-motivated perspective (ibid.)”. Berman and Slobin finally remark that “[t]hese formsare also found in the childrens narratives, but only occasionally across subjects andtexts (ibid.)”.
Thus the age group at our disposal is not optimal for studying the phenomenon ofinterest. Indeed we do not see much difference between the groups in the followingdomains:
– explicit setting of the reference time (‘in the night’)– packaging several events in one utterance (e.g., using ‘when’)– use of thematic connectivity markers (‘because’, ‘therefore’, ‘but’…)– use of temporal adverbials not fixing reference time (‘again’, ‘a long time’).
In fact, in both groups the vast majority of connectivity markers are of the additivekind (‘and’, ‘and then’, ‘and now’), just as in Berman and Slobin’s data for this agecategory, and this swamps the greater use of thematic connectivity markers observedin the control group.
There is one somewhat curious significant difference in the use of temporal adver-bials such as (the Dutch equivalents of) ‘suddenly’, ‘all of a sudden’, ‘immediately’,‘at once’ …which refer to an abrupt transition between two events, the second of whichalso occurs unexpectedly. In example 4.3.4 the first event is that of the frog being inthe jar, which ends abruptly as the frog escapes.
(13) Het was nacht. En Piet sliep. Zijn hond sliep op zijn bed. Opeens stapte de kikkeruit de fles.It was night-time. And Piet was asleep. His dog slept on his bed. Suddenly thefrog stepped out of the bottle. [8yrs, CG]
Such adverbials help the hearer in setting up the event structure, for instance becauseit introduces a distinction between background and foreground events; one can seethis clearly in example (13). In view of this function it is of some interest that ifone defines a corresponding strategy for control children18 as ‘use ‘suddenly’ (or its
18 This strategy increases the computational load of the speaker, and eases that of the hearer.
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 483
Fig. 3 Pictures 22–24 from “Frog, where are you?”
near-synonyms) three times or more’19 then 15% of the controls employs thisstrategy, and none of the children with ADHD; this difference is significant(p = 0.043).
4.3.5 The Perfects
We expected significantly less use of the perfects by children with ADHD, in particularof the past perfect. This is not quite what we observed. Overall, children with ADHDused more present perfects than the control children, but fewer past perfects; for thepast perfect the difference is near-significant (p = 0.062). If we look at individualchildren and count how often they use a past perfect, we do get a striking difference:38% of control children use the past perfect more than two times,20 against 11.5% ofthe children with ADHD, a significant difference (p = 0.041). One reason for thisis that the ADHD children use the past perfect much less often in the second half ofthe story. Consider for instance the final pictures of the story (reproduced in Fig. 3),where the past perfect would be highly appropriate.
The boy and his dog come to a log, and behind this log they see the frog. It turnsout the frog has found a mate, with whom he has made many little frogs. The readerwill have noticed that we just reproduced the story in the narrative present, but usingthe past tense one would get something like this;
(14) En toen zagen ze twee kikkers. En toen veel meer. En toen hadden ze de kikkerteruggevonden.And then they saw two frogs. And then many more. And then they had foundthe frog again. [7yrs, CG]
Now compare this to the opening scenes of the story, given in Fig. 2. Setting the scenerequires either the past perfect (15) (if the dominant tense of the story is going to bethe simple past), or the present perfect (16) (if the dominant tense is going to be thenarrative present):
19 This number is determined as the mean plus one standard deviation.20 This number is determined as the mean plus one standard deviation.
(15) Stefan en de hond die hadden een kikker gevangen. Die had die in de pot ged-aan. En die zat stevig vast.Stefan and the dog had caught a frog. He had put it in a jar. And it was firmlyshut. [9yrs, CG]
(16) Het is nacht. Jan zit naar zijn kikker te kijken die hij gevangen heeft en die hijin zijn potje heeft gestopt.It is night-time. Jan is looking at his frog that he has caught and that he has putin his jar. [9yrs, ADHD]
What is interesting here is that whereas in the opening scenes 1–3 there is no significantdifference between ADHD and CG with regard to either present or past perfect, theclosing scenes elicit significantly more (p = 0.016) past perfects from the controls;see Table 4. Semantically there is no reason for this difference between first and lastpictures, and one may therefore hazard the hypothesis that the computational burdenof the past perfect affects the subject only after a while.
4.3.6 Combining Strategies
The starting hypothesis of this investigation was (9), repeated here for convenience:
(17) Children with ADHD use a complexity-reducing strategy significantly moreoften than control children.
So far we have looked at specific strategies to reduce the complexity of tense pro-cessing. We now take a more global view, and look at the children who apply one ormore complexity-reducing strategies. For example, a child may use up all his com-putational resources by avoiding direct speech, thereby producing, say, more erraticshifts in the perfect. Both in case of excessive use of direct speech and of erratic tenseshifts the hearer must work hard to construct a coherent story, even though he may notunderstand why he has to work so hard. Thus, taking the point of view of the hearer,what is necessary is a general definition of complexity-reducing strategy, incorpo-rating the more specific strategies discussed above. Motivated by the analyses givenabove, we define the overall complexity-reducing strategy of a child as consisting ofthree components. A child employing one of these component strategies contributes apoint (or sometimes 0.5 point) to the number of points of its group. The cut-off valuesmentioned (5%, 9%, 12%) are determined as the mean plus one standard deviation.
(1) Avoiding perfect tenses We speak of a strategy when the child uses no perfecttense at all (1 point).
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 485
Table 5 Distribution of complexity-reducing strategies
Control group (N = 34) ADHD group (N = 26) p-value
(2) Avoiding tensed verbs We speak of a strategy when the child(a) uses tenseless utterances (no direct speech) in more than 5% of his or her
narration (0.5 point)(b) uses tenseless utterances (direct speech) in more than 9% of his or her narra-
tion (0.5 point).(3) Preference for direct speech We speak of a strategy when the child uses com-
plete direct speech utterances (tensed or tenseless) in more than 12% of his or hernarration (1 point).
We then get the pattern of results as given in Table 5. We see that the differencebetween the groups is now highly significant. Thus, the general hypothesis (17) seemsto receive some confirmation, even though some of the more detailed hypotheses,such as those about anchoring and connectivity, were not supported, at least in thisage group.
5 Conclusion: What can a Formalism do for You?
Let us first summarise the results obtained. We presented our main hypothesis as:‘children with ADHD use strategies for discourse production which reduce the com-putational burden on themselves, but increase that of the hearer’. We then identifiedseveral areas where we expected to see such strategies at work, mainly involving tenses(here including the perfects) and connections between utterances. In the latter domainwe observed hardly any differences between children with ADHD and controls. Thisis probably due to lack of statistical power; it is necessary to investigate older childrento see whether there really is a null-effect. In the former domain we found severaldifferences that are near-significant; combined into a general complexity-reducingstrategy as given in Sect. 4.3.6 the difference between the groups turned out to behighly significant. What we should conclude from this for ADHD is not an entirelystraightforward matter, since there is so much comorbidity in our population. But thisis a feature that affects research on ADHD in general.
The predictions concerning the use (or non-use) of verb tenses in ADHD werederived from a formal model of tense production and comprehension involving satis-faction of complex goals, together with neuropsychological evidence indicating dif-ficulties with goal maintenance and/or planning toward that goal. The formal modelis responsible for the specificity of the predictions. Without the formal model, butequipped only with, say, Trabasso and Stein’s general characterisation of narrativeas governed by a hierarchy of goals (Trabasso and Stein 1994), one expects some
123
486 Michiel van Lambalgen et al.
breakdown in the coherence of the story, as was indeed found by Purvis and Tan-nock (1997). The formal model allows one to be more specific about the computa-tional cost of the devices used to ensure discourse coherence. The model thus actsas a searchlight that allows one to see phenomena one would not have thought ofotherwise.
One final note of caution. The predictions on the use of verb tense in ADHD werenot derived from DSM-type diagnostic criteria, but rather from an EF deficit that isknown to occur in a considerable number of cases. A much more direct test of thetheory proposed here would thus be to take a sample of subjects known to have diffi-culties on the Shue and Douglas Go/NoGo task and have them do the narration task.Willcutt et al. (2005) claim that not all of ADHD can be explained through EF deficits.Given the fluidity of the ADHD diagnosis this shouldn’t be a cause for surprise, butit indicates that one ‘all’ children with ADHD to suffer from the problems reportedhere.
References
Aarssen, J. (1996). Relating events in two languages. Acquisition of cohesive devices by Turkish-Dutchbilingual children at school age. Tilburg, Netherlands: Tilburg University Press.
Baggio, G. (to appear). A semantic approach to the electrophysiology of tense. Language Learning.Berman, R. A., & Slobin, D. I. (Eds.) (1994). Relating events in narrative. Hillsdale, N.J: Lawrence Erlbaum.Blankenstijn, C., & Scheper, A. (2003). Language development in children with psychiatric impairment.
Published version of PhD thesis, LOT, Utrecht.Doets, K. (1994). From logic to logic programming. Cambridge, MA: The MIT Press.Kowalski, R. A. (1979). Logic for problem solving, volume 7 of Artificial Intelligence Series. North-Holland,
New York and Oxford.Kowalski, R. A. (1995). Using meta-logic to reconcile reactive with rational agents. In Meta-logics and
logic programming. pp. 227–242. MIT PressMayer, M. (1969). Frog, where are you? Dial books for young readers. New York.Ozonoff, S., Strayer, D. L., McMahon, W. M., & Filloux, F. (1994). Executive function abilities in children
with autism and tourette syndrom: an information-processing approach. Journal of Child Psychologyand Psychiatry, 35, 1015–1032.
Pennington, B. F., & Ozonoff, S. (1996). Executive functions and developmental psychopathology. Journalof Child Psychology and Psychiatry, 37, 51–87.
Pijnacker, J., Geurts, B., van Lambalgen, M., Buitelaar, J., Kan, C., & Hagoort, P. (2007). Conditionalreasoning in high-functioning adults with autism (Submitted).
Purvis, K. L., & Tannock, R. (1997). Language abilities in children with attention deficit disorder, readingdisabilities, and normal controls. Journal of Abnormal Child Psychology, 25(2), 133–144.
Roelofs, M. (1998). “Hoe bedoel je?” De verwerving van pragmatische vaardigheden. The Hague,Netherlands: Holland Academic Graphics.
Russell, J. (2002). Cognitive theories of autism. In J. E. Harrison, & A. M. Owen (Eds.), Cognitive deficitsin brain disorders (pp. 295–323). Dunitz, London.
Shue, K. L., & Douglas, V. I. (1992). Attention deficit hyperactivity disorder and the frontal lobe syndrome.Brain and cognition, 20(1), 104–124.
Steedman, M. (1997). Temporality. In J. van Benthem, & A. ter Meulen (Eds.), Handbook of Logic andLanguage.(pp. 895–938 Chap. 16). Elsevier Science.
Stenning, K., & van Lambalgen, M. (2007). Logic in the study of psychiatric disorders: executive functionand rule-following. Topoi, 26(1), 97–114. Special issue on Logic and Cognitive Science.
Trabasso, T., & Stein, N. L. (1994). Using goal-plan knowledge to merge the past with the present andfuture in narrating events on line. In M. H. Haith, J. B. Benson, R. J. Roberts, & B. F. Pennington (Eds.),The development of future-oriented processes, (pp. 323–352). University of Chicago Press.
van der Meulen, E. M. (2003). Attention-deficit hypercativity disorder in Dutch children. A family study ongenotype, phenotype and environment. Wageningen, Netherlands: Ponsen & Looijen.
123
Discourse Processing in Attention-Deficit Hyperactivity Disorder (ADHD) 487
van Lambalgen, M., & Hamm, F. (2004). The proper treatment of events. Blackwell: Oxford and Boston.Willcutt, E., Doyle, A. E., Nigg, J. T., Faraone, S. V., & Pennington, B. F. (2005). Validity of the executive
function theory of attentiondeficit/hyperactivity disorder: A meta-analytic review. Biological Psychiatry,57, 1336–1346.
![[Quantitative electroencephalogram analysis confirms the presence of frontal lobe deficit among attention deficit disorder with hyperactivity children]](https://static.documents.page/doc/80x56/6350a68bae531ce862039d98/quantitative-electroencephalogram-analysis-confirms-the-presence-of-frontal-lobe.jpg)
