Table 2.

Some hypothetical dependent variables in the experimental analysis of mand variability

Dependent variable	Operational definition	Example
Overall manding	The combination of independent variant and independent invariant manding.	See Adami et al. (2017; i.e., “total mands”).
Invariant manding	A response that is the same as the previous response in terms of topography, the stimulus selected, the modality selected, or a combination of these based on the experimental arrangement.	See Silbaugh et al. (2018; i.e., “independent invariant manding”).
Topographically variant vocal manding	A vocal mand topography that differs from the last vocal mand topography. A vocal mand topography is different if one or more words differ from the last vocal mand topography and begin following a 1-s or longer pause in vocalizations.	Saying “Apple please,” then 1 s later saying “Can I have a slice?” (see Fig. 2).
Topographically variant nonvocal manding	A nonvocal mand topography that differs from the last nonvocal mand topography, following a 1-s or longer pause in nonvocal manding.	Sign manding “I want apple,” then sign manding “Apple slice please” after no less than a 1-s pause (see Fig. 2).
Variant manding across topographical modalities	A mand topography that differs in modality (e.g., sign or vocal) from the last mand topography, following a 1-s or longer pause in manding, even if two modalities co-occurred.	If a speaker gestures to apple slices, then asks “Can I have one?” the second response is variant because the participant switched topographical modalities. Similarly, if a participant gestures to apple slices, then simultaneously gestures and says “Apple please,” the second response consists of a combination of vocal and nonvocal modalities and therefore differs from the prior response, which occurred in only one topographical modality (see Fig. 3).
Variant manding across nonvocal selection-based modalities	A mand modality selection that differs from the last mand modality selection, after no less than a 1-s pause, regardless of the topography (e.g., touching, picking up) of the selection.	Selecting a picture card that says “Apple please,” then pressing a microswitch that plays a prerecorded message “Apple please.” Or pressing a red microswitch, then tapping an icon on a tablet application (see Fig. 4).
Variant manding across topographical modalities and selection-based modalities	An instance of manding that differs in the overarching category of modality (i.e., topography based or selection based) from the last instance of manding, following a 1-s or longer pause in manding.	Saying “apple,” then pressing a microswitch that says “apple.” Or tapping an icon on a tablet application that says “apple,” then signing “apple” (see Fig. 5).
Variant nonvocal manding across stimuli within a selection-based modality	An instance of selection-based manding that differs in the stimuli selected within a given modality (e.g., tablet application displaying multiple icons) from the last instance of manding, regardless of topography, following a 1-s or longer pause in manding.	If a participant taps the “please” icon to mand for an apple, then taps a series of icons to form the sentence “I want apple,” the second response is variant because different stimuli within the tablet application were selected. However, if the participant taps the “please” icon once, then taps the “please” icon again, the second response is invariant (see Fig. 6).
Variant manding across nonvocal topographies and across stimuli within a selection-based modality	An instance of nonvocal manding that differs in the stimuli selected within a given modality (e.g., tablet application displaying multiple icons) from the last instance of manding, and differs in topography, following a 1-s or longer pause in manding.	For example, if a participant taps the “please” icon with their index finger, then taps a series of icons to form the sentence “I want apple” with their thumb, the latter is variant because different stimuli within the tablet application were selected by a different topography. However, if the participant taps the “please” icon with their elbow once, then taps the “please” icon with their elbow again, the latter response is invariant because the response did not differ in terms of both modality and topography. Similarly, if the participant taps the “please” icon with their elbow, then taps the “apple” icon with their elbow, the second response is still invariant because the topography did not vary (see Fig. 7).
Variant manding across nonvocal topographies and across selection-based modalities	An instance of manding that differs in nonvocal topography and selection-based modality from the last instance of manding, following a 1-s or longer pause in manding.	If a participant selects a picture card by pointing to it, then presses a microswitch with their hand, the second response is variant because it differed both in terms of the nonvocal topography and the selection-based modality. However, if the participant taps an icon on the tablet with their pointer finger, then taps the picture card with their pointer finger, the second response is invariant because although the selected modality varied, the topography did not vary (see Fig. 8).