Action performance and action-word understanding: Evidence of double dissociations in left-damaged patients

Abstract

It has been proposed that language and action representational systems overlap when the tasks used to assess them involve the same stimuli and require abilities acquired at similarly early developmental stage. We matched variables at task and stimulus level to test this hypothesis in a group of 12 left-damaged patients (and 17 controls). At the patients' group level, we replicated previously reported correlations between linguistic and nonlinguistic tasks. When performances were analysed individually, however, double dissociations were observed between the ability to imitate pantomimes and the ability to produce and comprehend the corresponding action verbs, as well as between the ability to use tools and the ability to comprehend the corresponding tool nouns. These findings suggest that processing action words is independent of the ability to produce the associated object-directed actions. Double dissociations were also found between the ability to comprehend action verbs and the ability to comprehend tool nouns. Moreover, action and tool naming showed differential effects of age of acquisition, suggesting that the two word categories meet the lexical organization by word class (nouns and verbs), even when related to identical action concept. Dissociations at behavioural level are supported by anatomical dissociations shown in the analysis of patients' lesions.

Keywords:

• Aphasia
• Embodied cognition
• Word comprehension
• Action recognition
• Noun–verb dissociation

Acknowledgments

This project was funded by a PRIN (Progetto di Rilevante Interesse Nazionale) given to R.I.R. by the Ministry of Italian University and Research. We thank Claudio Luzzatti for insightful discussion when designing the study, Pietro Chiarello for help in realizing the video-clips used as experimental stimuli, Paola Mengotti for help in collecting data, and three anonymous reviewers for their valuable comments. Liuba Papeo is now at the Department of Psychology, Harvard University, Cambridge, MA, USA. Gioia A. L. Negri is now at IRCCS “E. Medea”, Assoc. La Nostra Famiglia, Udine, Italy.

Notes

¹A second response to any of the items provided by at least 5% of the panel was considered as an alternative correct response in the experimental phase (e.g., “aprire” to unlock, was the acceptable alternative for “chiudere”, to lock).

² This rating scale was use to measure the semantic distance between pairs of words (one target and one potential distractor of the same category of the target, i.e., action verb or object noun). Each target appeared in more than one pair. The mean semantic distance was computed for each pair. Pairs were selected so that the mean semantic distance of noun pairs (4.69 ± 1.65 SD) was not significantly different from the mean semantic distance of verb pairs (4.75 ± 0.42 SD); t(14) = 1.76, p > .1.

³Interrater reliability was computed using the concordance correlation coefficient for the assessment of concordance in continuous data (Lin, 2000). Correlation coefficient was satisfactory, as it was .97 between Rater 1 and Rater 2, .97 between Rater 2 and Rater 3, and .98 between Rater 1 and Rater 3.

⁴Although the small sample size did not allow running parametric statistics, it is worth noting that the error analysis provided no indication that in the 5 patients with impaired imitation (according to Crawford's t scores), the percentage of semantic errors in naming and comprehension (means: 3.33% and 76%, respectively) was increased, as compared with patients not impaired in imitation (27.38%, semantic errors in naming; 87.5% semantic errors in comprehension).

⁵Note that AoA can also affect verb retrieval (e.g., Colombo & Burani, 2002; Morrison et al., 2003), depending on the aspects of word processing tapped by a given task (see Boulenger et al., 2008).