Table 2. Real verbs and correct responses in the past-participle and present-tense tasks.

In selecting the items, verbs that might trouble patients (e.g., morire `die') were avoided, as were onomatopoeic verbs, recent borrowings, and verbs which may involve additional, complex morphological structure, such as reflexive verbs (e.g, avvedersi `notice'), and prefixed verbs for which the unprefixed form of the verb is a real word (e.g., perseguire `pursue', seguire `follow').

The real past-participle verbs consisted of 30 irregular verbs matched group-wise to 30 regular verbs on lemma frequency (irregular: 3.27; regular: 3.36; t<1), frequency of the infinitive (irregular: 1.90; regular: 1.91; t<1), and masculine singular past-participle frequency (irregular: 1.34; regular: 1.34; t<1). Frequency matching was based on standard frequency counts (out of 496,000 words) (De Mauro, Mancini, Vedovelli, & Voghera, 1993); values were augmented by one and natural-log transformed prior to matching, as in previous studies (Ullman, 1999). The regular verbs in the past-participle task all belong to morphological class I (infinitive in –are), and form their past-participle by adding –ato to the infinitival stem (e.g., port-are → port-ato `carry'). The irregular verbs were primarily class II, but included 2 class III verbs. The infinitival forms of the regular and irregular verbs did not differ in length either orthographically (regular: 7.77; irregular: 7.87; t<1) or phonologically (number of syllables: regular: 3.50; irregular: 3.43; t<1).

The real present-tense items consisted of 16 irregular verbs and 16 regular verbs, matched on lemma frequency (irregular mean: 4.64; regular mean: 4.59; t<1), frequency of the infinitive (irregular mean: 2.96; regular mean: 2.98; t<1), and first person singular inflected form frequency (irregular mean: 1.84; regular mean: 1.73; t<1). The regular verbs in the present-tense task were all drawn from morphological class I. The irregular verbs were taken from all three morphological classes (1 from class I, 7 from class II, 8 from class III). They were irregular in the first person singular either by changing the present-tense stem in an unpredictable way (uscire → èsc-o; n=8), or through the addition of a stem augment (e.g., ven-ire → ven-g-o; n=8). Note that bére and dire were both classified as irregular verbs because the present-tense stem is not predictable from the infinitival form for either verb. In contrast to the past-participles, the regular present-tense infinitives were actually longer than the irregular present-tense infinitives, both orthographically (regular: 7.25; irregular: 6.06; t(30)=2.66, p=0.01), and phonologically (number of syllables: regular: 3.38; irregular: 2.88; t(30)=2.83, p=0.008). Thus if length has any effect at all, it would be expected to make regulars harder, biasing the stimuli against an irregular deficit.

Finally, we examined whether the regular and irregular verbs differed on consonant density, calculated as the number of consonants divided by the number of syllables of a given form. This measure captures important aspects of the phonological complexity of the verb forms (Bird, Lambon Ralph, Seidenberg, McClelland, & Patterson, 2003; Joanisse & Seidenberg, 1999; McClelland & Patterson, 2002; Ullman et al., 1997), while avoiding the potential confound of any phonological length differences between regulars and irregulars. The regular and irregular verbs did not differ on consonant density for either the past-participle or present-tense items, on either their infinitival forms (past-participle items: regular: 1.14, irregular: 1.14; t(58)<1; present-tense items: regular: 1.06, irregular: 0.99; t(30)=1.12, p=0.27) or their inflected forms (past-participle items: regular: 1.14, irregular: 1.21; t(58)<1; present-tense items: regular: 1.09, irregular: 1.18; t(30)<1).

A. Past-participle		B. Present-tense
Regular	Irregular	Regular	Irregular
affrontare → affrontato confront	accèndere → accéso kindle	aiutare → aiuto help	aagire → agisco
ascoltare → ascoltato listen to	appèndere → appéso hang	arrivare → arrivo arrive	andare → vado go
baciare → baciato kiss	aprire → apèrto open	cercare → cerco seek	bére → bévo drink
ballare → ballato dance	bére → bevuto drink	chiamare → chiamo call	acògliere → còlgo gather
camminare → camminato walk	chièdere → chièsto ask for	cominciare → comincio begin	dire → dico tell
cenare → cenato have supper	chiùdere → chiuso shut	curare → curo take care of	afinire → finisco end
cercare → cercato seek	cògliere → còlto gather	donare → dono donate	arimanére → rimango remain
collegare → collegato join	córrere → córso travel	girare → giro turn	asalire → salgo climb
comprare → comprato buy	difèndere → diféso defend	guardare → guardo watch	sapére → sè know
confermare → confermato confirm	dipèndere → dipéso depend	ingannare → inganno deceive	ascégliere → scélgo choose
consegnare → consegnato deliver	dirìgere → dirètto direct	negare → nego deny	sedére → sièdo sit
creare → creato create	discùtere → discusso discuss	pagare → pago pay	atenére → tèngo have
cucinare → cucinato cook	distìnguere → distinto distinguish	parlare → parlo speak	trarre → traggo pull
dedicare → dedicato dedicate	divìdere → diviso divide	pensare → penso think	udire → òdo hear
domandare → domandato ask	erìgere → erètto build	studiare → studio study	uscire → èsco go out
girare → girato turn	giùngere → giunto join	trovare → trovo find	avenire → vèngo come
inventare → inventato invent	mòrdere → mòrso bite
lavare → lavato wash	muòvere → mòsso move
lavorare → lavorato work	nascóndere → nascósto hide
mangiare → mangiato eat	offrire → offèrto offer
mescolare → mescolato mix	pórre → pósto put
parlare → parlato speak	prèndere → préso take
portare → portato carry	protèggere → protètto protect
saltare → saltato jump	rìdere → riso laugh
scaricare → scaricato unload	rispóndere → rispósto answer
sognare → sognato dream of	scégliere → scélto choose
suonare → suonato sound	scéndere → scéso descend
tagliare → tagliato cut	scrìvere → scritto write
trovare → trovato find	vìncere → vinto win
usare → usato use	vìvere → vissuto live

^a= takes augment