The laterality quotient is calculated using all the answers on the ehi, with the formula: (pos-neg)/(pos+neg)*100 )
The Edinburgh Handedness Inventory is a measurement scale used to assess the dominance of a person's right or left hand in everyday activities, sometimes referred to as laterality. The inventory can be used by an observer assessing the person, or by a person self-reporting hand use. The latter method tends to be less reliable due to a person over-attributing tasks to the dominant hand.
The EHI has several measures that can help assess a person's laterality.
| answer | value | nominal | lq | lq_cat | lqa_cat |
| Left dominance | -2 | left | -100 | left | left |
| Left preference | -1 | left | -40 | left | ambidexter |
| No preference | 0 | ambidexter | 0 | right | ambidexter |
| Right preference | 1 | right | 40 | right | ambidexter |
| Right dominance | 2 | right | 100 | right | right |
The easiest measure from the EHI is the nominal laterality value, which is just the answer to the first question on hand preference when writing. This simple index just treat negative answers as "left" dominance, positive number as "right" dominance, and a 0 as ambidextrous. Note: The original paper by Oldfield (1971) does not explicitly state a category for "Ambidextrous". It is very rare that a person does not have a clear preference on writing hand, even if they can write with both hands. This category is only added in this package to handle the possible case of someone answering "No preference".
| min | max | category |
| -2 | -1 | left |
| 0 | 0 | ambidexter |
| 1 | 2 | right |
The total score of the EHI is more than just summing the values for each answer. The laterality quotient (LQ) uses the answers to all the questions. The LQ can take values from -100 to 100, and is calculated by taking the sum of all positive answers subtracting the sum of absolute values of the negative answers, divided by the sum of both, and multiplied by 100.
katex::katex_html(equation)The laterality index is based on the laterality quotient (above) and categorises answers into to categories, Left and Right.
The Oldfield (1971) paper mentions "indeterminate handedness" a couple of times in the paper, but the case for "true" ambidextrous is not made, and as such the inventory does not have official categories for that.
As the index is based on the quotient, that ranges from -100 to 100, getting a perfect 0 LQ is very unlikely, and as indicated in the paper, such score is assumed to belong to the Right hand part of the scale.
| min | max | category |
| -100 | -1 | left |
| 0 | 100 | right |
An alternate laterality index is also often employed, where scores between -40 and 40 are treated as ambidextrous.
One row of data should refer to a single questionnaire answered, and as such, if a person has answered multiple times, these should appear on separate rows with columns identifying ID and time point per observation.
Oldfield, RC (March 1971) The assessment and analysis of handedness: The Edinburgh inventory. Neuropsychologia. 9 (1): 97–113. doi:10.1016/0028-3932(71)90067-4
Verdino, M; Dingman, S (April 1998). Two measures of laterality in handedness: the Edinburgh Handedness Inventory and the Purdue Pegboard test of manual dexterity. Perceptual and Motor Skills. 86 (2): 476–8. doi:10.2466/pms.1998.86.2.476
Knecht, S; Dräger, B; Deppe, M; Bobe, L; Lohmann, H; Flöel, A; Ringelstein, E-B; Henningsen, H (December 2000). Handedness and hemispheric language dominance in healthy humans. Brain. 123 (12): 2512–8. doi:10.1093/brain/123.12.2512.
ehi_compute_lq(data, cols = matches("^ehi_[0-9][0-9]$"))data.frame containing ehi data
tidyselected columns of all ehi data
numeric
Other ehi_functions:
ehi_compute(),
ehi_factorise_lq(),
ehi_factorise_nominal()