Extended Abstract
Introduction
Neuropsychological evidence in brain injury patients has shown that the two grammatical categories of nouns and verbs are processed in different areas of the brain [1]. A review of behavioral, brain imaging, and electrophysiological studies in individuals with brain injury indicates that verbs are more likely to be affected than nouns [2-5]. In general, verbs are inherently more complex than nouns due to their pivotal role in a sentence as well as their morphological complexity [6], and create more semantic processing load [7, 8]. Therefore, their processing needs more support from meaning selection mechanisms as well as the integration of cortical and subcortical regions [9]. 
In particular, the processing of action verbs is related to the activity of motor and pre-motor areas of the brain [10]. Recent studies have shown that, during understanding and expressing the action verbs, the same areas of the brain involved in planning and performing the movements that describe those words are active [11-14]. The association between language defects and damage to motor areas of the brain has been shown in patients with movement disorders, especially Parkinson’s disease [15-20]. The results of these studies have led to the formation of the theory of embodied cognition [21, 22]. Linguistic and cognitive assignments are useful tools for testing the hypotheses of this theory. In evaluating action word processing, three types of tasks are used: 1. Word-retrieval tasks; 2. Semantic processing tasks [17, 23-26]; and 3. A combination of these two types of tasks [20].
Naming is the most common task of lexical examination [15, 27-29]. Action verbal fluency [18, 19, 30], as another word-retrieval task, requires semantic, lexical, or grammatical analysis [31]. One of the limitations of these tasks is to provide verbal answers and not separating the speech motor planning stage from other pre-motor stages of language processing. In addition, it is not possible to draw definitive conclusions as to whether the observed damage is due to word retrieval problems or the involvement of specific processing levels such as semantic encoding. To understand whether the action verb processing defects are due to word access problems or special damage at any level of language processing, a special task needs to be designed. 
The Semantic Similarity Judgment (SSJ) test targets lexical-semantic encoding and, by distinguishing it from other levels of linguistic encoding, can detect damage at this level of processing. To perform this test, the target word at the top and the two related and unrelated semantic words at the bottom of the page are presented in a triangular arrangement. Then, participants are asked to judge which of the two lower words is more semantically similar to the upper word. Due to the clear comparison and judgment between the meaning of the words and, finally, the decision that is made, its implementation requires access to deeper and controlled processing levels; therefore, it puts more cognitive load on semantic sources. 
The use of tasks that specifically address semantic processing can provide stronger support for evidence of semantic impairment in patients with motor neuron diseases [20]. Due to the lack of a valid test for judging the semantic similarity of verbs and nouns in Persian language and considering its importance, the purpose of this study is to design a SSJ test of two categories of action verbs and non-action nouns in Persian language and to evaluate its content validity in a qualitative manner.
Materials and Methods
This is a methodological study. The development of SSJ test was done in three steps: Selecting appropriate lexical stimuli, designing triplets of nouns and verbs, and determining the psycholinguistic and lexical features of stimuli.
Selecting appropriate lexical stimuli
At this stage, appropriate lexical stimuli including 80 non-action concrete nouns and 70 action concrete verbs in different occurrence frequencies and lengths (number of syllables, phonemes and letters) were selected. For each word, a semantically related word was chosen. Content validity was determined qualitatively with the help of 3 experts (one linguist and two speech-language pathologists) and inappropriate words were eliminated according to them. The semantic similarity of the pair of semantically related words (target words and semantic related words) was determined based on a 7-part scale with the opinion of 4 experts (3 speech-language pathologists and one linguist). Criteria of semantic similarity between nouns was existence of similarity in conceptual properties (including two functionally-related and category-related properties) and perceptual properties [32]; and for verbs, it was existence of similarity in action and activity between two words.
Designing noun/verb triplets
For each pair of semantically related words, an action verb or a non-action noun that had no semantic connection with the target word was selected. In general, the words were chosen in such a way that for comparison and judgment, the minor aspects of the meaning of the words to be considered, which increases the cognitive load of this task. At this stage, the content validity was evaluated qualitatively based on the appropriateness of the semantically unrelated word and also its relationship with the target word, by two experts (two speech- language pathologists) and inappropriate words were removed and replaced. In this way, two nooun and verb triplets were designed. Each of the triplets consisted of a target word, a semantically related word, and a semantically unrelated word
Determining the psycholinguistic and lexical features of stimuli
Lexical features included number of syllables, number of phonemes, number of letters, number of phonological and orthographic neighbors, and frequency of occurrence. Information about the frequency of each word was extracted from the Persian language database [33]. Psycholinguistic features included action association [34], imageability, age of acquisition, and level of familiarity, which were collected and extracted using a 7-point scale and based on the opinion of 18 experts and native Persian-speaking parents (14 specialists and 4 native Persian speakers aged 31-40 years with a mean age of 35 years) [16, 34] face-to-face and online (via e-mail). Nouns with very little or no action association, as well as verbs with high to very high action association were remained and others were removed. Finally, 102 non-action nouns (34 triplets of nouns) and 102 action verbs (34 triplets of verbs) that were matched for lexical and psycholinguistic features (except for action association) were chosen.
Results
In this section, the results of the analysis are presented in two sections; one related to the two lists of nouns and verbs and one related to the triplets of nouns and verbs.
Results related to the two lists of nouns and verbs
After selecting the appropriate words and examining their content validity in a qualitative manner, the lexical characteristics of each word were extracted based on available sources. Then their psycholinguistic features were collected, extracted and analyzed using a 7-point scale, based on the opinions of 18 experts and a number of parents. Table 1 shows the descriptive statistics of the lexical and psycholinguistic characteristics of the two sets (nouns and verbs). In order to compare the mean of lexical and psycholinguistic characteristics between the two sets, the independent t-test was performed at a predetermined alpha level of 5%. Before performing independent t-test, Levene’s test was performed to test the equality of variances between the two groups. For variables in which variance equality was not reported, a modified degree of freedom was used. 

Table 2 shows the results of the independent t-test. The results show that the two word lists did not have a statistically significant difference (P≥0.05)in the following variables: number of syllables (t177.35=1.18, P=0.23), number of letters (t178.53=0.63, P= 0.52), number of phonological neighbors (t202=-0.08, P=0.93), number of orthographic neighbors (t202=-0.63, P= 0.52), word frequency (t202=-0.49, P=0.62), familiarity (t202=0.87, P=0.38), age of acquisition (t202=1.68, P= 0.09) and imageability (t182.44=1.09, P= 0.27);however, the difference between them was significant in terms of the mean number of phonemes (t202=-2.27, P=0.02) and mean degree of action association (t202=-57.38, P= 0.000) which was negligible (mean difference=0.58).
Results related to the noun/verb triplets
The mean number of syllables, phonemes and letters in each of the triplets were in a range of 2.33-4.33, 5.33-11.33 phonemes and 4.66-8, respectively. Table 3 shows the descriptive statistics of the word length of noun/verb triplets. The results of independent t-test showed no significant difference in the mean number of syllables (t66=1.16, P= 0.24), phonemes (t66=-1.32, P= 0.19), and letters (t66=0.83, P=0.40) between triplets (Table 4).

Discussion
The purpose of the present study was to introduce and design a SJJ test of Persian nouns and verbs for patients with developmental and acquired brain injuries and to determine its content validity. The SJJ test targets lexical semantic encoding by comparing minor aspects of lexical meaning. The lexical stimuli used in this test included 102 non-action concrete nouns with low action association and 102 action verbs with high action association. In this test, nouns and verbs differed only in terms of action association. This contrast has been used in many studies. The words of the two categories were matched for lexical characteristics such as number of syllables, phonemes, letters, phonological neighbors, orthographic neighbors, and frequency of occurrence as well as psycholinguistic characteristics including action association, imageability, age of acquisition, and level of familiarity. 
The results of independent t-test showed that there was no significant difference in lexical and psycholinguistic features (P>0.05), except for the number of phonemes and action associations (P≥0.05) between the two sets of nouns and verbs, where the difference in the mean number of phonemes between the two sets was very small. The words of each grammatical category were classified into 34 triplets. The results of independent t-test showed that there was no significant difference in the mean word length of each category between 34 triplets of nouns and verbs (P≥0.05). It can be said that the SSJ test with 102 Persian verb stimuli and 102 Persian noun stimuli is a suitable tool for conducting research on Persian speech, language and cognition. By establishing coordination in lexical and psycholinguistic features of the two sets of word stimuli, the effect of these variables on the test results of patients can be controlled and eliminated, and only the lexical-semantic encoding of nouns and verbs, and the semantic feature of action are examined.
The SSJ test designed in this study has three basic features: 1. This test evaluates semantic encoding at the controlled (non-automatic) processing level; thus, creating a greater cognitive load on semantic resources. The word items used in this test are such that its implementation requires the comparison and judgment of minor semantic differences between words. This will further increase the cognitive load of this test; 2. this test evaluates the semantics of action. One of the important aspects of the designed SSJ test was the attention to the semantic characteristics of action. 
Discussion
The approach of embodied cognition to conceptual knowledge is that the motor system has the main role in the semantic representation of action-related words [35-38]. For this purpose, we used action verbs with high action association. According to the theory of embodied cognition, the motor system is involved in semantic processing, but its involvement can occur at different levels of processing. Tasks with different processing loads produce different neuroanatomical and temporal patterns of motor system activity. Fernando et al.’s (2013) study [17] showed that the motor system participates at the semantic processing of action words at two levels: automated and controlled. One of the features of the designed SSJ test is that it provides a kind of processing of action words at a controlled level; 3. It can evaluate and compare the lexical- semantic processing of two grammatical categories of Persian verbs and nouns. The two categories differ based on the semantic feature of action, but the words in both categories are all concrete.
Overall, the designed SSJ test can be a good tool for examining the processing of semantic feature of movement in people with various neuromotor and cognitive-linguistic disorders such as acquired and developmental stuttering, Parkinson’s disease, aphasia, multiple sclerosis, ALS and developmental disorders. It can be used to test the hypotheses of the theory of embodied cognition. Another important point is the type of patients’ responses to this test. Since patients with neuromotor impairments also show impairments in speech motor performance, providing nonverbal response eliminates the effect of speech motor impairment on the test response and allows the lexical-semantic encoding to be evaluated more thoroughly. 
Because the semantic complexity and cognitive load of verbs are greater than those of nouns [39], the existence of two different grammatical categories (nouns and verbs) with different semantic complexities can distort the comparison of different semantic characteristics of action. By adding action nouns to non-action concrete nouns, or abstract verbs next to action verbs, the confound effect of the word category type can be eliminated. To control other confounding variables that are not considered in this study, it is suggested that when performing this test on groups with brain injuries, the control group should be used to compare the two categories of non-action noun and action verb between the two groups of injured and healthy.
Conclusion
The purpose of this study was to introduce, design and determine the content validity of the SSJ test to examine the lexical- semantic processing of Persian action verbs and non-action concrete nouns. The SSJ test, in addition to allowing the comparison of two different grammatical categories, can be used to examine action word processing and test the hypotheses of the theory of embodied cognition in order to evaluate the role of the motor system and the effect of damage to this system on linguistic and cognitive function, especially in patients with neuromotor and cognitive impairments such as aphasia, dementia, especially Alzheimer’s disease due to semantic defects [40], developmental and acquired stuttering, Parkinson ‘s disease and other movement disorders as well as developmental language disorders such as special language impairment due to dysfunctional semantic system [41].
Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Social Welfare and Rehabilitation Sciences (Code: IR.USWR.REC.1397.170).  
Funding
The present paper was extracted from the PhD. thesis of the first author, Department of Speech Therapy, University of Social Welfare and Rehabilitation Sciences.
Authors' contributions
Investigatoin: Tabassom Azimi; Conceptualization, writing-editing the final version of maniuscript: All authors. 
Conflicts of interest
The authors declared no conflict of interests.
Acknowledgements
The authors would like to thank Department members of Speech Therapy of Social Welfare and Rehabilitation Sciences, specially Mrs. Maryam Malekian.