The most comprehensive scale for capturing the subjective effects of specific drugs is the ► Addiction Research Center Inventory (ARCI) developed by Haertzen et al. (1963), which measures subjective effects to a number of specific classes of drugs including ► morphine, ► LSD, and ► amphetamine, and among other symptoms tries to capture a euphoric-dysphoric continuum. With 550 true-false items, the inventory is problematically long for use as a real-time measure, so many investigators will restrict the questions to just those related to the specific drug of interest.
An important, and often overlooked, issue in studies of emotion and mood involves how to have participants rate their moods. Most studies have utilized either visual analog scales (VAS) or likert scales (LS). VAS consist of two verbal anchor descriptors that are placed on either end of a continuous line. Respondents provide ratings on VAS by indicating the point on the line that best represents the intensity of their current psychological experience. VAS may be considered to provide interval-like data in that they provide rank-order information about rating values and equal spacing exists between neighboring values along the entire scale continuum. Unfortunately, because the continuum lacks verbal descriptors, it is impossible to ascertain the qualitative intensity that corresponds to an intermediary rating. This means that intermediary ratings made by different individuals are not readily comparable. In contrast, to the VAS, LS consist of numeric points arranged along a discrete continuum, with intensity descriptor labels placed at both anchor points, and the intermediary numeric points. These labels have the advantage of leading individuals to use the intermediate ratings in a more qualitatively similar way. However, such scales are problematic, in that unless the intensity descriptors are truly equidistant, the applied numeric values do not represent the true quantitative (intervallike or ratio-like) differences in ratings. This is particularly problematic for bipolar scales (for instance, those running from unpleasant to pleasant), in that studies examining ratings of verbal descriptors have revealed that the magnitude differences of terms typically used to mark the low to moderate intensities cover a smaller distance than terms used to mark the moderate to the most intense anchors. This means a change in ratings between two descriptors in the lower intensity part of the scale cannot be considered equivalent to a change in two descriptors at the higher part of the scale (Fig. 1).
Recent research has led to the development of labeled magnitude scales (LMS), which attempt to address the weaknesses of the VAS and LS (Lishner et al. 2008). LMS utilize a visual analog scale framework, but includes descriptors that are placed along the scale at empirically determined intervals derived from rating studies of the intensity descriptors. Such scales also often use ''most imaginable'' instead of a term such as ''extreme'' as the highest intensity anchor in order to limit ceiling effects. To date, the LMS approach has not been widely used in psychopharmacological research, but this type of approach can be easily integrated into existing scales. However, it may be necessary to verify that the factor structure
Visual analog Neutral
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