1.1. The animacy constraint

One of the cross-linguistically most relevant constraints on the order of nouns in spoken and written language is based on animacy: Nouns with animate referents tend to be produced earlier than those with inanimate referents (Sauermann & Höhle, 2018; Lohmann, 2013; Branigan, Pickering, & Tanaka, 2008; Grewe, 2007; Demuth, Machobane, Moloi, & Odato, 2005; McDonald et al., 1993). Beyond the simple dichotomy (animate versus inanimate), a more gradual continuum of animacy has been proposed (Paczynsky & Kuperberg, 2011). Such graded rankings can be justified by different criteria (Yamamoto, 1999), with the ability of autonomous movement (self-propelledness) being the most important feature for preschool children (Piaget, 1978; Opfer & Gelman, 2011). However, a dichotomous classification seems sufficient for our purpose.

How does animacy influence word order? A first type of account attributes the effect to lexical or conceptual access. Bock and Warren (1985) attributed facilitated access to animate concepts to the fact that they have more semantic features or pathways, arguing that these features accelerate activation of an item (‘concept accessibility’). A second type of explanation highlights the standard order of thematic roles in the lexical entry of a verb and its theta grid. According to this account, agent and experiencer tend to occupy earlier positions and, being capable of self-controlled actions and feelings, usually animate referents fill these positions. This approach can be located at the interface between syntax and semantics (Grewe, 2007). However, Dewart (1979) advanced a purely syntactic explanation according to which the tendency to produce animate items first is considered to be due to the fact that they usually serve as subjects. For SVO-languages like German (which has a non-rigid word order³), this syntactic approach could at least partly explain the animacy constraint.

1.2. Rhythm and *LAPSE

The phonological factor of interest is the propensity for an alternating rhythm in speech (Principle of Rhythmic Alternation, Selkirk, 1984). In German, as in English, the underlying trochaic pattern of prosodic word structure often yields this alternation of stressed and unstressed syllables in spoken language. Ideally, this alternation is not disturbed as in (1).

However, in everyday speech, disruptions of this rhythmic structure are inevitable and do occur naturally. Rhythmic deviations may appear as stress clashes or stress lapses (Selkirk, 1984; Hayes, 1995); the former denoting an encounter of two or more stressed syllables, the latter a sequence of two or more unstressed syllables. A prosodic constraint in speech, *CLASH, requires that sequences of stressed syllables should be avoided. Accordingly, another prosodic constraint, *LAPSE, requires that sequences of unstressed syllables should be avoided. One way to visualize the rhythmic structure of phrases or sentences is a metrical grid (Halle & Vergnaud, 1987). In such a grid, the degree of a syllable’s prominence is shown by the number of beats that are accumulated above it, and rhythmic structure is defined by the horizontal distances of equally prominent syllables. Hence, in a rhythmically alternating structure, the number of beats should alternate from one syllable to the next syllable. According to Halle and Vergnaud (1987), the number of beats is determined by principles of the prosodic hierarchy (see below). Since we are only dealing with the trochaic pattern in (1) as well as its violation in structures with *LAPSE and *CLASH, Figure 1 is limited to two levels of prominence (i.e., the distinction between stressed and unstressed syllables).

Figure 1

Simplified metrical grids for a rhythmic sentence (upper panel), a sentence with stress clash (middle panel), and a sentence with stress lapse (lower panel). The two rhythmic violations *CLASH and *LAPSE are highlighted in bold. Layer 1 represents the default beat for every syllable. Layer 2 represents the beat for every stressed syllable.

1.2.1. *LAPSE in the prosodic hierarchy

A stress lapse is not merely considered a rhythmic imperfection concerning the sequential ordering of stressed and unstressed syllables. Rather, in research on prosodic phonology, a stress lapse necessarily involves a deviance from an optimal hierarchical representation.

In prosodic phonology, utterances are divided into prosodic units, which are layered according to their size. Hence, every utterance can be represented as a hierarchic tree structure (see Figure 2). The strict layer hypothesis (Selkirk, 1984) postulates that lower units in the prosodic hierarchy should be exhaustively parsed into the next higher unit (‘exhaustivity constraint’⁵). Thus, syllables are dominated by feet (F), which in turn are dominated by prosodic words (PW) and phonological phrases (PHP). For our purposes, the interplay of syllables and feet is most relevant. In German, English, and other languages, syllables are grouped into left-headed, maximally binary feet with the left syllable being stressed (e.g., Brúder, ‘bróther’).

Figure 2

Example for the prosodic hierarchy. The letters s (strong) and w (weak) in the lowest level of the tree label the syllables as being strong/stressed or weak/unstressed. The red line represents non optimal syllable parsing. There is a lapse structure consisting of two weak syllables, –es and the, highlighted in bold.

Figure 2 illustrates the prosodic hierarchy and its relation to exhaustivity and *LAPSE. As a foot should consist of at most two syllables, with one syllable being stressed, the first three syllables in the example Lane, kiss and -es can each be parsed into a foot. In terms of exhaustivity, they form an optimal structure, as they are parsed exhaustively into the next higher domain, i.e., prosodic feet. In contrast, the fourth syllable the cannot be parsed into one of the surrounding trochaic feet and must therefore be adjoined directly to the prosodic word, thereby violating the exhaustivity constraint (marked in red). At the same time, this structure engenders a lapse with two adjacent unstressed syllables. Under the assumption that feet are maximally disyllabic and trochaic, stress lapses generally incur a violation of the exhaustivity constraint. Figure 2 also illustrates that this doesn’t hold for stress clash: Although it causes a rhythmic violation, the first two syllables Lane and kiss are parsed exhaustively, either forming their own foot or at least forming the head of a foot (see Gerken, 1996).

1.3. The interplay of ANIM and *LAPSE

McDonald et al. (1993) examined the impact of both animacy and rhythm on word order in English speech production. Adult participants were asked to memorize phrases like doll and attic using mental images as memory aids in order to combine the two conjuncts of a phrase. Subsequent to a variable number of mental images, participants wrote down the phrases they could remember without any order to be maintained between or within the phrases. One of the conjuncts was monosyllabic whereas the other one was either a trochee as in (5a) and (5b) or an iamb as in (5c) and (5d) (McDonald et al., 1993 [Exp. 6]). Participants were more likely to sequence the conjuncts as in (5a) and (5d) thus showing a preference for alternating rhythm and lapse-avoidance.

Interestingly, lapse avoidance was only an effective determinant for word order as long as the conjuncts didn’t vary in terms of animacy, whereas animate items were produced first, irrespective of rhythmic aspects. This preference is exemplified in (6) (McDonald et al., 1993 [Exp. 5]). When there was a combination of animate and inanimate items within a phrase, participants seemed to ignore prosodic violations (see [6]). Accordingly, the animacy constraint ANIM seems to be stronger in adults’ English speech production than the rhythmic constraint *LAPSE.

Whether the same holds for child language and German is still an open question. On the one hand, findings from speech perception attest the special importance of prosodic constraints in child language (Schröder & Höhle, 2011, Gutman, Dautriche, Crabbé, & Christophe, 2015; Morgan & Demuth, 1996) and results from speech production support the prosodic licensing hypothesis (Demuth, 2007). At the same time, animacy clearly affects word order in child language, too (Demuth, 2005; Prat-Sala et al., 2000; Drenhaus & Féry, 2008; Byrne & Davidson, 1985). To determine the degree to which ANIM and *LAPSE affect the choice of a particular word order, we set out to directly compare the interplay of these constraints in child versus adult speech production.

1.4. The present study

In the present study, we tested speech production by German preschoolers (Experiment 1) and adults (Experiment 2), eliciting coordinated noun phrases (Klavier und Ratte, ‘piano and rat’) from picture prompts. We systematically varied a) the animacy and b) the stress pattern of the nouns involved. The order of the conjuncts that the participants chose reveals the extent to which participants comply with the critical non-syntactic constraints on word order, namely ANIM (animate > inanimate) and *LAPSE (avoid two unstressed syllables). Experiment 3 was conducted as a control Experiment.

2.2. Results

On average, each of the 18 participants produced ~21 valid conjoined noun phrases (range: 11 to 28) on the basis of 30 stimuli pictures. This corresponds to 385 valid phrases obtained in the experiment. Interestingly, in the subset with both nouns being iambs, out of the 90 produced noun phrases 48 were valid (53.3%), while in the subset with both nouns being trochees, 75 of the 90 recorded phrases were valid (83.3%). In the remaining mixed subset (containing iambs and trochees in each pair) out of 360 noun phrases 262 were valid (72.8%). In the following description the ratio between two manifestations of each factor is used to provide a summary of the descriptive statistics, followed by two mixed effect models with the full data set and a subset.

Figure 7 summarizes the results with respect to the following factors: Position of the items (that is the visual stimulus position on the screen), word frequency, animacy, and prosody and their influence on conjoined phrase ordering in Experiment 1. In 61% of cases, children named the top right conjunct before the bottom left one, indicating a general preference for this order. However, no child used one of the orders exclusively. Thirteen of the 18 children started the conjoined noun phrase with the top right item in more than 50% of their utterances; the remaining five children generally preferred the reverse order. Word frequency of the individual nouns did not appear to systematically affect conjunct ordering, as could be expected given that item pairs were approximately matched for word frequency. Overall, the more frequent noun was named first in 48% of cases, as can be seen in Figure 7. The factor animacy clearly affected word order. For the subset of stimuli in which the nouns differed in terms of animacy, the animate noun was named first in 65% of cases (see Figure 7).

Figure 7

Mean ratio of conjunct order in Experiment 1 (children, conjunction with und, ‘and’) with respect to the following factors: Position (proportion upper right first), word frequency (proportion higher frequent first), animacy (proportion animate first), and prosody (proportion iamb first). Each plot represents the influence of one factor on word order. The bold line within each box indicates the median across participants. Grey circles represent means of individual participants. Chance distribution (.5 ratio) is indicated by the vertical dotted line. The four upper plots refer to the dataset where the relevant factors vary whereas the lowest plot refers to the subset where animacy doesn’t vary in the item pairs.

Examining all pairs with rhythmically varying nouns (n = 262), both orders are equally present: 52% of all item-pairs with mixed word rhythm led to rhythmically alternating realizations (iamb > trochee; see Figure 7). However, when studying the subset of data in which there is no animacy distinction between the two depicted objects (either both pictures animate or both inanimate, n = 128 coordinate phrases), a preference for rhythmically alternating realizations is revealed (59%).

We also assessed whether the age of the children matters for the ordering of conjuncts. To this end, we studied the correlations of age and the other variables of interest. For each participant, we calculated the proportion of responses that a) adhere to the predetermined standard order, b) observe the animacy constraint (in item pairs that vary with respect to animacy), and c) abide by the principle of rhythmic alternation. We then correlated these proportions with the participant’s age (see Figure 8).

Figure 8

Scatterplot showing the proportion of animate-first responses as a function of age. The slope of the blue regression line corresponds to the correlation coefficient R.

The proportion of A > B orders does not appear to vary systematically with age (r = –0.088, p = .73, see the scatterplot in the Appendix). However, the strength of the observed animacy constraint (animate > inanimate) clearly increases with age. This is shown in Figure 8 depicting a moderate positive correlation between age and preference for the animate > inanimate order (r = .55, p = .019). No significant developmental pattern is observable for the rhythmic constraint (r = .21, p = .41, see the scatterplot in the Appendix).

We employed a generalized linear mixed-effects regression model (glmer, Bates, Mächler, Bolker, & Walker, 2015) in R statistical software (version 4.0.2, R Core Team, 2020) to evaluate the main effects of ANIM and *LAPSE and their interaction on the ordering of the conjuncts. Apart from ANIM and *LAPSE, we also included age and the interactions between a) age and ANIM, and, for completeness, b) age and *LAPSE. Age was counted in months, centered to the mean age of all participants (64.4 months) and rescaled to year (division by 12). Given the findings by McDonald et al. (1993), we especially expected *LAPSE to affect ordering if ANIM is mute, i.e., when both pictures have the same animacy value. We therefore introduce ANIM_Diff (coded as +.5 when the pictures differ in terms of animacy, otherwise –.5), and included its interaction with *LAPSE in the model. Finally, the effect of word frequency was included, coded as the difference in frequency (log) between the two depicted conjuncts. To account for the variability due to individual participants and individual item pairs, participant and item were included as random intercepts. In the models we report below, we did not include random slopes for the fixed effects, because the model failed to converge.

The model confirms a significant effect of ANIM. Transforming the corresponding coefficient of 1.53 (logit) to odds ratio (4.6) by exponentiation, we can interpret this coefficient in the following way: Deviating from the standard order (A > B in Figure 5) in favor of the animacy constraint is nearly 5 times as likely as deviating from it to the detriment of the animacy constraint. The significant interaction of ANIM and age (logit: .861; odds ratio: 2.37) reflects the above-mentioned correlation (see Figure 8) and suggests that (for the age range studied here) aging by 12 months makes it roughly twice as likely to observe the animacy constraint. The significant *LAPSE:ANIM_Diff interaction confirms that adhering to the rhythmic constraint (logit –1.876) is roughly 6 times as likely when the pictures do not vary in terms of animacy compared to when there is an animacy difference between them. All other main effects and interactions do not reach conventional levels of significance (see Table 4).

Given the *LAPSE:ANIM_Diff interaction, we tested the effect of *LAPSE specifically in the subset in which item pairs did not vary with respect to animacy. In this subset, as shown in Figure 7, participants were more likely to follow the rhythmically alternating order iamb “und” trochee. The corresponding generalized linear model for this subset included the same factors as the full model, except for the predictors related to animacy and the corresponding interactions. The model statistics are summarized in Table 5.

The significant main effect of *LAPSE (logit .83 – odds ratio 2.29) confirms that, when faced with item pairs that do not vary in terms of animacy, participants were roughly twice as likely to deviate from the predetermined standard order in favor of a rhythmically alternating rendition than to deviate from it to the detriment of rhythmic alternation.

2.3. Discussion of Experiment 1

In Experiment 1 we set out to test whether animacy (ANIM) and rhythm (*LAPSE) have an impact on the ordering of nouns in conjoined phrases in the speech production of German preschoolers. For this purpose, we designed a picture naming study: Participants were asked to name pairs of pictures using conjunctional phrases without determiners (e.g., Pilot und Klavier, ‘pilot and piano’) and with no prespecified order. Pictures were coupled and presented diagonally in a square with one picture being placed lower left and the other upper right. Due to the design (we used animate and inanimate items that were either trochaic or iambic) the chosen sequences yielded rhythmically alternating or disrhythmic phrases which either complied with the animacy constraint or violated it.

The results show that the preschoolers as a group prefer to start with the upper right picture (i.e., deviate from the arbitrarily set standard sequence). This is consistent with a study by Knudson et al. (2014) who found that the left-right bias (that is commensurate with the reading direction) only comes into effect after school enrollment. Next to this general effect of presentation layout, we found a strong effect of animacy favoring animate referents being named first in line with findings reported by Prat-Sala et al. (2000). Additionally, the effect of animacy correlated positively with the age of the children. Since the age range of our participants is rather large, especially in relation to the relatively small sample size, the results need to be interpreted with caution. However, the clear age effect of ANIM is noteworthy. Interestingly, this result is consistent with the possible reasons for animacy effects mentioned in the introduction: For example, the account of ‘concept accessibility’ which was proposed by Bock and Warren (1985) assumes the higher number of semantic pathways leading to an ‘animate’ lexical entry to accelerate word access. Since the lexical entries are getting richer and more diverse during language development, it seems plausible that an effect of animacy due to concept accessibility increases with age.

The effect of rhythm was weaker and only significant for the subset of item pairs in which animacy was held constant. The rather weak effect of *LAPSE, our rhythmic constraint, might be due to the fact that in order to produce a rhythmic sequence (Pilót und Rátte, ‘pilot and rat’), the children had to start with an unstressed syllable (Pi- in this example). According to Gerken (1994a), toddlers avoid initial unstressed syllables since they cannot be parsed into a foot. It is possible that this avoidance of unparsed initial syllables (or the higher accessibility of trochees as opposed to iambs, see Schiller, Fikkert, & Levelt, 2004) affected our results and thus weakened the effect of *LAPSE. The higher number of invalid data points with iambs as opposed to trochees supports this explanation. Nevertheless, an effect of rhythm on conjunct order is effective in spite of these potential counteracting forces. In the next experiment we set out to test how German adults sequence bare nouns in conjoined phrases and how the discussed constraints affect their choices.

3.2. Results

Two participants used one of the orders exclusively (either always A > B or always B > A, cf. Figure 5 above). Due to their lack of variation, these responses are uninformative for our hypothesis and were therefore excluded from further analysis. From the remaining participants, we obtained 950 valid responses. Figure 9 summarizes the results with respect to the factors position (that is the visual stimulus position on the screen), word frequency, animacy, prosody, and their influence on conjunct ordering in Experiment 2.

Figure 9

Mean ratio of conjunct order in Experiment 2 (adults, conjunction with und, ‘and’) with respect to the following factors: Position (proportion upper right first), word frequency (proportion higher frequent first), animacy (proportion animate first), and prosody (proportion iamb first). Each plot represents the influence of one factor on word order. The bold line within each box indicates the median across participants. Grey circles represent means of individual participants. Chance distribution (.5 ratio) is indicated by the vertical dotted line. The four upper plots refer to the dataset where the relevant factors vary whereas the lowest plot refers to the subset where animacy doesn’t vary in the item pairs.

The conjunct presented in the bottom left was named first in 65% of cases, indicating a general preference for this order. Word frequency of the individual nouns did not appear to systematically affect ordering of the conjuncts. The factor animacy (ANIM) does appear to bias word order: 58% of the animate items served were named first in the phrase (see Figure 9). However, the data don’t suggest a clear effect of rhythm (*LAPSE): 51% of the iambic items were mentioned before the trochaic ones. When studying the subset of data in which there is no animacy distinction between the two presented objects (both animate or both inanimate, n = 316 coordinate phrases), the distribution of responses shows a preference for rhythmic sequences (in 55% of cases the iambic noun was named first).

A generalized linear mixed-effects regression model (glmer, Bates et al., 2015) was employed in R statistical software (version 4.0.2, R Core Team, 2020) to evaluate the effects of ANIM, *LAPSE, their interaction, the effect of uniformity versus difference regarding the animacy of the depicted objects (ANIM_Diff), and its interaction with *LAPSE, as well as word frequency on word order. To account for the variability due to individual participants and items, these were included as random intercepts (we did not include random slopes due to convergence errors). Apart from the significant intercept (reflecting the clear preference for the left before-right order), the model revealed a significant effect of ANIM (logit .819 – odds ratio ~2.27), suggesting that deviating from the standard sequence in favor of ANIM is roughly twice as likely as deviating from the standard order to the detriment of ANIM. Also, the significant interaction of *LAPSE and ANIM_Diff suggests that any effect of rhythm is contingent upon whether or not the depicted objects vary in terms of animacy. All other main effects and the interaction did not significantly affect conjunct ordering. In a second step, we isolated animacy-invariant item pairs. In this subset, there was a significant effect of *LAPSE (logit: .656 – odds ratio: 1.93), suggesting that deviation from the standard order was nearly twice as likely when this served rhythmic alternation in the response. The model statistics for both the full data set and for the subset are summarized in Table 6.

3.3. Discussion of Experiment 2

Experiment 2 was a replication of Experiment 1 conducted with young adult participants. In line with Experiment 1, we found a clear influence of ANIM on ordering conjuncts and a significant impact of *LAPSE on conjunct order for the subset of stimuli that do not vary in terms of animacy. In contrast to the preschoolers, the group of adult participants strongly preferred to name the items placed in the lower left quadrant first, which is in line with Knudson et al. (2014) who showed that the left-right bias emerges with reading proficiency. This relatively strong bias regarding the dependent variable may curb the other effects and thus explain the considerably weaker effect of ANIM in the group of adult participants (odds ratio ~2) when compared to the preschoolers (odds ratio ~4). The effect of *LAPSE in the subset analysis, however, was more comparable in the two experiments (odds ratios in both groups are around ~2).

In order to produce a rhythmic sequence, participants had to name iambic nouns before trochaic ones. Since Schiller et al. (2004) found shorter naming latencies for trochees, rhythm needs to counteract this tendency when favoring a fronted iamb. This might have weakened the results, similarly to the earlier mentioned prosodic issues with the unparsed initial syllable in our rhythmic structures. Again, we would like to highlight the fact that despite this potentially counteracting effect of word form retrieval, the rhythmic constraint *LAPSE did influence word order.

In order to shed light on the question whether latencies of word form retrieval might have influenced our results, we conducted Experiment 3 as a control Experiment. Further, by exchanging und, ‘and,’ with oder, ‘or,’ the target structure yields another deviation from alternating rhythm, i.e., a stress clash (two or more stressed syllables in a row), as illustrated in Figure 10.

Figure 10

Simplified metrical grid illustrating a stress lapse (left panel) and a stress clash (right panel). The violations of *LAPSE and *CLASH are bold-faced. Layer 1 represents the default beat for every syllable. Layer 2 represents the beat for every syllable bearing lexical stress.

4.2. Results

On average, each of the 28 participants produced 29.6 valid conjoined noun phrases (range: 27 to 30) on the basis of 30 stimulus pairs. This yielded 857 valid phrases obtained in the experiment. Figure 11 summarizes the results with respect to the following factors: position, word frequency, animacy, and prosody and their influence on conjoined phrase ordering in Experiment 3.

Figure 11

Mean ratio of conjunct order in Experiment 3 (adults, conjunction with oder, ‘or’) with respect to the following factors: position (proportion upper right first), word frequency (proportion higher frequent first), animacy (proportion animate first), and prosody (proportion iamb first). Each plot represents the influence of one factor on word order. The bold line within each box indicates the median across participants. Grey circles represent means of individual participants. Chance distribution (.5 ratio) is indicated by the vertical dotted line. The four upper plots refer to the dataset where the relevant factors vary whereas the lowest plot refers to the subset where animacy doesn’t vary in the item pairs.

In 65% of the cases, participants named the bottom left conjunct before the top right one, indicating a clear general preference for this order. One participant used one of the orders (lower left > upper right) exclusively and was therefore excluded from further analysis. Twenty-four of the 27 remaining participants started the conjoined noun phrase with the referent in the bottom left picture in more than 50% of their utterances.

The factor animacy (ANIM) affected word order in the whole dataset: 54% of the animate items were sequenced before the inanimate ones (see Figure 11). Again, the data don’t show a clear effect of rhythm (*LAPSE, 51% of the iambic items were named before the trochaic ones). When studying the subset of data in which there is no animacy distinction between the two presented objects (both animate or both inanimate, n = 282 coordinate phrases), no clear preference for naming trochees or iambs first is revealed either (52% iambs first).

A generalized linear mixed-effects regression model (glmer, Bates et al., 2015) was employed in R statistical software (version 4.0.2, R Core Team, 2020) to evaluate the effects of ANIM and *LAPSE, their interaction, as well as of logarithmized word frequency on word order. To account for the variability due to individual participants and items, these were included as random intercepts. Apart from the significant intercept (reflecting the clear preference of left before right-order), the model reveals a significant effect of ANIM. Transformed to odds ratio (1.56), this effect appears to be somewhat weaker than what was observed in Experiment 2. Even though frequency does not seem to affect word order when the data is averaged (see Figure 11), frequency turns out to significantly affect conjunct ordering. *LAPSE and the interaction between ANIM and *LAPSE yield non-significant results. In a second step, we isolated animacy-invariant item pairs. In this subset, as shown in Figure 11, there was no significant effect of rhythm or frequency. The model statistics are summarized in Table 7.

4.3. Discussion of Experiment 3

In Experiment 3 we set out to test whether the results which we interpreted as an effect of prosody in Experiment 1 and 2 could be alternatively explained by potential artefacts of any item-specific properties. This was done by changing the instructions that were given to the participants: Instead of using the monosyllabic conjunction und (‘and’), participants were instructed to use the trochaic coordinative disjunction oder (‘or’) between the two nouns. Consequently, both sequences of iambs and trochees yielded disrhythmic structures so that none of them should be preferred over the other (if both rhythmic constraints are equally strong, they may cancel out each other). A tendency to front iambs in this design could mean that our effects in the first two experiments aren’t necessarily rhythmic in nature but potentially caused by item-specific properties of our iambic nouns or their corresponding pictures (e.g., visual salience). To sum up, in Experiment 3 we predicted no effect of rhythm but an effect of animacy, and this is exactly what we found.

4.3.1. Comparison of subset analyses of Experiments 2 and 3

While we obtained, as predicted, a significant effect of *LAPSE in the subset analysis in Experiment 2 (see above), and no significant effect of *LAPSE in the subset analysis of Experiment 3, the difference between these two effects is relatively small, as the confidence intervals (coefficient estimate +/– 2xSE) associated with these effects clearly overlap to a non-negligible amount (confidence interval for *LAPSE in subset analysis of Experiment 2: [0.086, 1.226], Experiment 3: [–.231, .961]).⁹ It is therefore possible that a re-run of Experiment 3 would yield an effect of *LAPSE as well.

Recall that we argued that any effect of stress lapse in trochee-initial phrases (Káfer óder Klavíer) would be neutralized by stress clash in iamb-initial phrases (Klavíer óder Káfer). Furthermore, the large overlap in the confidence intervals of the coefficients might well have to do with the fact that oder, in spite of its trochaic stress pattern, usually receives only very limited prosodic prominence on its stressed syllable and certainly no accent. The effect of stress clash in case of iamb-initial phrases might therefore be minuscule and not strong enough to override the effect of stress lapse in trochee-initial phrases.¹⁰ Therefore, we cannot exclude that iamb-initial phrases with oder might be felt to be nearly as rhythmic as those with und. Figure 12 illustrates the prominence relations in a metrical grid, including a third level covering the accent bearing nouns as opposed to the conjunction that bears lexical stress but no accent (see Selkirk, 1984, among others). The difference in terms of accentability might weaken the stress clash in this structure. However, the stress lapse is not affected by this.

Figure 12

Metrical grid with three layers. Layer 1 represents the default beat for every syllable. Layer 2 represents the beat for every stressed syllable. Layer 3 represents the beat for every accent bearing syllable. The grid illustrates a stress lapse (left panel) and a stress clash (right panel). The (potential) violations of *LAPSE and *CLASH are highlighted in bold.

5.1. The results in a nutshell

In Experiment 1 children preferably produced animate items before inanimate ones, showing a significant influence of ANIM on word order. These results are consistent with findings reported by Prat-Sala et al. (2000) for English speaking children. The effect of ANIM correlated positively with age, which is rather surprising in preschoolers, given that Bassano et al. (2013) reported ceiling effects of animacy in children aged only 2;5 years. However, taking possible reasons for an effect of animacy into account, this result is plausible: For example, the notion of ‘concept accessibility’ (Bock & Warren, 1985) assumes the higher number of semantic pathways leading to an ‘animate’ lexical entry to accelerate word access. Since the lexical entries are getting richer and more diverse during language development, an effect of animacy due to concept accessibility might increase with age. Also, syntactic and syntactic-semantic accounts which see the effect of ANIM in relation to typical requirements of the usually sentence initial subjects or agents, are in accordance with this result—older children have more experience with these constructions which most likely increased their influence on children’s serialization.

Furthermore, participants preferred to name iambs before trochees, and by doing so, avoided disrhythmic structures. However, the rhythmic effect only reached the conventional level of significance for the subset of data in which the two referents did not vary with respect to animacy. Consequently, the experiment lends some support to our first hypothesis, in line with the prosodic licensing hypothesis (Demuth, 2007). That is, while conjunct order is demonstrably affected by ANIM and *LAPSE, the scope of the first constraint clearly surpasses the second one. In Experiment 2, adult participants showed a remarkably similar pattern in sequencing nouns with ANIM dominating *LAPSE. These results add to, and corroborate, the findings by McDonald et al. (1993) for English speaking adults. In Experiment 3, we did not find any effect of word stress—since both sequences yielded a disrhythmic structure, this pattern was predicted. Thus, this null result is in line with our prosodic interpretation of the results in Experiments 1 and 2. The effect of ANIM remained significant in Experiment 3. In the following, we will discuss potential weaknesses of our design, and explore the workings of the semantic and rhythmic constraints that might offer possible explanations for the relatively weak effect of *LAPSE.

5.2. Potential prosodic artefacts

As described in the introduction, this study was inspired by McDonald et al. (1993), who tested adult English participants and found that both animacy and rhythm affect the word order of conjuncts—the latter only as long as animacy doesn’t vary. Crucially, in their experiment, they used disyllabic and monosyllabic items. To exclude any effect of word length (Lohmann & Takada, 2014), we used two types of disyllabic items—trochaic and iambic ones. In the following, we will outline the potential prosodic and psycholinguistic consequences of this choice.

As described above, participants had to name iambs before trochees to produce a rhythmically alternating sequence in Experiments 1 and 2, which yielded an unstressed initial syllable. Note, however, that even the structure that yields rhythmic alternation involves a prosodic violation. This is illustrated in Figure 13: In the rhythmically alternating structure the first syllable Pi- cannot be parsed into a foot, leading to a violation of exhaustivity. Since Gerken (1994a, among others) showed, that especially children avoid (initial) unparsed syllables, our design might provoke counteracting effects of prosody that could explain that the expected effect of rhythm remained rather weak.

Figure 13

Violations of exhaustivity in the prosodic hierarchy for both word orders in Experiment 1 and 2. The red lines represent ‘illegal’ syllable parsing. The left panel shows a rhythmically alternating sequence, the right panel a *LAPSE sequence.

At this point, it is worthwhile to stress that despite the issue of an unparsed initial syllable, we actually found a rhythmic effect. We might conclude that the preference for rhythmic alternation had a stronger influence on the chosen word order than the violation evoked by an unparsed initial syllable. Additionally, the prosodic structure in the case of rhythmic alternation (Figure 13, left panel) violates the exhaustivity constraint only once while the sequence with a lapse does so twice (Figure 13, right panel): In the lapse structure, the syllables Pi- and und can’t be parsed into a foot yielding two violations of exhaustivity. Gerken (1996) showed that the probability to omit unstressed syllables, correlates with the number of exhaustivity-violations in young children. Thus, while not prosodically perfect, the rhythmically alternating structure is prosodically more well-formed than the disrhythmic structure. This may have led to a (small) preference for the former compared to the latter.

5.3. Potential rhythmic process

This study is built on the assumption that the German conjunction und, ‘and’ is unstressed. However, in a sentence repetition task, Vogel, van de Vijver, Kotz, Kutscher, and Wagner (2015) showed that the prominence degree of usually unstressed function words varies in favor of an alternating rhythm. The authors found increased syllable durations of the pronoun es, ‘it,’ if surrounded by unstressed syllables. Transferring their finding to our target structure, the originally unstressed conjunction in our disrhythmic sequences (surrounded by two unstressed syllables) might be processed similarly to the originally unstressed pronoun in Vogel et al. (2015)—that is, with a higher level of prominence. Figure 14 illustrates this possibility in a metrical grid (for rhythmic adjustments in metrical grids see Nespor & Vogel, 1986). However, the fact that we still found an effect of *LAPSE suggests that any possible phonetic adjustment (beat insertion) did not invalidate our assumptions.

Figure 14

Metrical grid with three layers. Layer 1 represents the default beat for every syllable. Layer 2 represents the beat for every stressed syllable. Layer 3 represents the beat for every accented syllable. The left panel illustrates the metrical grid of the structure violating *LAPSE (in bold). The right panel illustrates the sequence with a rhythmically motivated beat insertion on the syllable und, ‘and’ resulting in a rhythmically alternating structure.

5.4. Potential artefacts of word form retrieval

Another potentially confounding factor is related to the costs of word form retrieval. Given that, in German, the iambic stress pattern is less frequent than the trochaic one, iambic words may result in increased processing effort in speech production. Since, in our design, participants had to name iambs before trochees to produce a rhythmically optimal phrase (Klavíer und Rátte, ‘piano and rat’), increased processing difficulty with the iambic structure could explain the rather weak effect of *LAPSE on serialization. Indeed, Schiller et al. (2004) found that English speaking adults need more time for naming iambs than they do for naming otherwise comparable trochees. Consequently, there could be counteracting effects of prosody and word form retrieval with shorter naming latencies for trochees (trochee > iamb) and a preference for naming iambs first to yield rhythmic structures (iamb > trochee).

Confirming the particular difficulty with iambic words (see also Gerken, 1994a) the children in Experiment 1 made more mistakes with iambic items than with trochees, although both were carefully familiarized in the same way. For example, participants made some mistakes naming the pictures for Ballón (‘balloon’), Regál (‘shelf’), Gespénst (‘ghost’), and Pilót (‘pilot’) using synonyms like Géist for Gespénst (‘ghost’), or semantically related words like Schránk (‘cupboard’) for Regál (‘shelf’), or Flúgzeug (‘plane’) for Pilót (‘pilot’). In some cases, they used more specific words like Héißluftballon (‘hot-air balloon’) for Ballón (‘balloon’) or they couldn’t find any word to name the picture at all. A phrase with any of these variations was considered as invalid yielding less data points in structures involving iambs.

In any case, the effect of rhythm was detectable despite this possible counteracting effect of word form retrieval. Nevertheless, one might argue that at least in Experiment 1, which was conducted with children, the effect of rhythm might have been stronger without the differing degree of effort retrieving trochees and iambs.¹¹

5.5. Semantic and rhythmic constraints and the scope of speech planning

The effect of ANIM in our experiment can probably be attributed to the lexical-semantic level and possibly also to visuo-semantic processing of the words and pictures involved. When producing isolated conjoined noun phrases, participants did not have to assign the items to any thematic roles or syntactic functions. Therefore, explanations relating to the syntactic level seem unlikely. Rather, it seems plausible to assume an easier lexical access for animate compared to inanimate items. Indeed, for adult participants, Proverbio, Del Zotto, and Zani (2007) found that naming latencies for animate words are faster than for inanimate ones. Such an eased access could be due to a larger quantity of semantic features or pathways leading to these features for animate as opposed to inanimate items (Bock & Warren, 1985). More specifically, an eased access could be related to increasing grades of a referent’s animacy (Yamamoto, 1999) enhancing its ‘concept accessibility’ (Bock & Warren, 1985). For example, given the criterion of self-paced movement (‘self-propelledness’), it seems to be reasonable that the attributed ability of autonomous movement may facilitate access to the lexical entry of a referent, as it can be associated with different situations and in different motions and has therefore more semantic pathways leading to it compared to an inanimate object.

Furthermore, effects of ANIM on word order in naming two pictures in a conjoined noun phrase could be due to visual salience. In an eye tracking study, Carniglia, Carputi, Manfredi, Zambarbieri, and Pessa (2012) showed that there is a bias for fixations to pictures with animate referents compared to those with inanimate referents. The former were earlier, longer, and more often fixated than the latter. As a consequence, our effect of ANIM might also be due to a visual bias in favor of animate items, with a possibility of a first seen – first planned – first named – mechanism. With visual prominence being controlled in our material in a pretest, an explanation of ANIM just based on visual complexity or dominance is not very likely though.

In sum, it appears that an attentional bias for animate objects (that may be grounded in some kind of visual and/or semantic salience) would suffice to explain the animacy effect in our data. Accordingly, speakers would name the more attention-grabbing animate noun first and then move on to name the second object. It would thus not be necessary for participants to directly compare the semantic features of the two objects. In order to produce rhythmically alternating structures on the other hand, speakers have to consider and compare the prosodic makeup of both nouns and the whole phrase. To abide by the rhythmic constraint, the scope of speech planning therefore needs to be considerably larger as opposed to the animacy constraint (for further discussion in the context of speech production models, see Section 5.6).

However, other explanations cannot be excluded. In particular, a tendency to produce animate nouns before inanimate ones could also be based on statistical properties of the speech input. This input typically consists of sentences and phrases so that syntactic or syntactic-semantic mechanisms, like the usual order of theta roles or syntactic functions, could be indirectly responsible for tendencies in the serialization of conjoined nouns (‘indirect syntactic explanation’). Further research is needed to clarify this question.

5.6. Semantic and rhythmic constraints in a speech production model

Apparently, ANIM and LAPSE are effective on different levels of speech planning. Which levels these are and how our results could fit into a model of speech production will be discussed in the following. First, we need to address the fact that our rather artificial structure of two bare noun phrases neither fits into a model of single word production, nor does it need all aspects of a model for whole sentences or beyond.

5.7. The present task in a speech production model

Apart from the artificial character of isolated conjoined noun phrases, the task of naming two objects in response to a visual stimulus differs from encoding some intention or coherent preverbal message: Participants have to name two unconnected objects in response to two drawings. This means they need to retrieve two semantically and syntactically unrelated lexical entries. Meyer, Sliderink, and Levelt (1998, referred to as MSL) conducted an eye tracking study with the exact target structure (two nouns without determiner with ‘and’ in between). Their stimuli were also two drawings of objects but placed next to each other (left and right) on the screen. They found that “the viewing times depended systematically on the time needed to retrieve the phonological form of the object names.” (MSL, p. 32).

According to their results, “the speakers completed the conceptual and most of the linguistic processing for one object before initiating the shift of gaze to the next object” (MSL, p. 32). Additionally, about 50% of their participants moved their gaze from the second picture back to the first picture during speech onset (MSL, p. 32). This implies, following the authors, that those participants had retrieved also the second word form by the time they started speaking.

Transferring these findings to the example Löwe und Pilot (‘lion and pilot’), the speaker has already retrieved the complete lexical entry of the first fixated picture Löwe (‘lion’) before she starts to look at the second one, Pilot (‘pilot’). Also, she has retrieved some parts of the lexical entry of Pilot before she starts speaking. Assuming that Löwe und Pilot (or Pilot und Löwe) is an IP which is computed as a single unit during grammatical encoding (following Calhoun, 2010), the speaker already retrieved the phonological form of one word and some information about the lexical entry of the other word while computing this IP. Consequently, she already has access to the metrical structure of one word and possibly of the other. In those cases, in which she looked back at the first picture, she should have accessed the phonological form of both words (according to MSL, gaze shifts back to the first item were only observed after full word access of the second item). If the latter is the case, rhythmic constraints could be effective already during IP formation—which interacts with positional processing, and thus with word order.

In the present example, the disrhythmic sequence Löwe und Pilot could be ‘rearranged’ into the rhythmically alternating structure Pilot und Löwe during grammatical encoding where prosody interacts with positional processing. Due to the specific task, it is possible that some participants already retrieved the metrical structure of both words when IPs are constructed, allowing rhythmic constraints to be effective during grammatical encoding. Consequently, in the context of this specific task and target structure, the effect of *LAPSE could be integrated into the model. In this framework it also makes sense that ANIM shows a relatively strong effect (presumably already operative in the preverbal message), while the effect of *LAPSE is much weaker—only happening during IP formation in those cases in which the metrical frame of both words has been retrieved already.

5.8. Final summary

This study demonstrates that both animacy and rhythm affect the ordering of bare noun conjuncts in German, and they do so in both preschoolers’ and adults’ speech production. We found a consistent effect of animacy (a preference for naming animate referents before inanimate ones) in all experiments, in line with results by Prat-Sala et al. (2000, among others). Effects of rhythm (i.e., the preference for conjunct orders that yield a rhythmic alternation of stressed and unstressed syllables) were only detectable when the animacy of the conjuncts involved was held constant. This result is consistent with findings by McDonald et al. (1993). Our experiments show that both the animacy effect and the rhythmic effect hold for preschoolers as well as adult speakers of German. For the group of preschoolers, the preference for naming animate referents first increases with age. We have no evidence for a corresponding developmental change regarding the influence of rhythm on word order choice.