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There are four main types of preference assessments:  single stimulus, paired stimulus, multiple stimulus, and free operant.  Catalyst currently supports collecting data in single, paired, and multiple stimulus preference assessments with free operant assessments coming in the near future.

 


SINGLE ITEM METHOD

The single item presentation method of conducting stimulus preference assessments (SPAs) is sometimes referred to as a “successive choice” assessment.  Stimuli, such as objects or activities, are presented sequentially, one at a time, in random order.  Typically, duration measures of “interaction” or “engagement” with each stimulus are used to identify highly preferred stimuli.


Advantages:  easy and quick to administer, ease of training staff in administration, useful for individuals who lack complex choice making skills since only one stimulus is presented at a time

Disadvantages:  does not provide a hierarchy of reinforcers, may produce false positives since many students will play with object as opposed to doing nothing during the interval

Fisher et al., 1992 found that when participants’ functioning level allowed them to discriminate between multiple stimuli delivered simultaneously, presenting them as such was more representative of a participant’s preference than in a single-stimulus presentation 


Details Regarding Single Item Stimulus Assessments in Catalyst

Stimulus Array:  Items are presented one at a time and only once during each session.

Scoring/Results:  Results are presented as duration of engagement with the item.

Termination Criteria:  The session is terminated when all trials are completed.

 


PAIRED STIMULUS METHOD

The paired stimulus method of conducting stimulus preference assessments (SPAs) is sometimes referred to as a “forced choice” assessment.  Stimuli, such as objects or activities, are presented sequentially, in pairs, in random order.  Every stimulus is presented systematically with every other stimulus at least twice (ideally, once on the left and once on the right to control for position bias).  The individual’s choice is recorded following each presentation, and stimuli can then be ranked based on selection percentage (selections/presentations X 100).

Paired stimulus assessments are generally more time-consuming than single item assessments; however, paired stimulus assessments can compare stimuli with one another to establish relative preferences.


Advantages:  provides a hierarchy of reinforcers (i.e., differentiates between the relative strength of reinforcers)

Disadvantages:  more complex and time consuming to administer than single stimulus assessment, may not be suitable for individuals who present with difficulties scanning multiple items or making choices.

 

Details Regarding Paired Stimulus Assessments in Catalyst

Stimulus Array:  Items are presented 2 at a time and compared with every other stimulus item twice (once with the item on the left and once with the item on the right, to control for position bias). 

Scoring/Results:  Results are presented as percentage of times the item was selected (# of times the item was selected / # of times the item was presented X 100).  The number of trials during the assessment is determined by the number of stimulus items being assessed (taking into consideration that every item is presented with every other item twice).

Termination Criteria:  The session is terminated when all trials are completed.

 


MULTIPLE STIMULUS METHOD

The multiple stimulus method of conducting stimulus preference assessments (SPAs) may reduce the time required for conducting an SPA that compares stimuli by presenting multiple stimuli at once, rather than in pairs.  Using these types of assessments, stimuli are presented in groups of three or more, with or without “replacement.” 

In a multiple stimulus WITH replacement (MSW), when a stimulus is selected, it is replaced on the next presentation.  For example, if a food item is consumed, an identical food item replaces the first in the subsequent stimulus array.  In a multiple stimulus WITHOUT replacement (MSWO), the selected stimulus is withheld (not replaced) on the subsequent presentation.  In other words, the array decreases by one stimulus item after each presentation until each has been selected or the individual fails to select one of the array.

Advantages:  provides a hierarchy while still being efficient, require significantly less time to administer than the paired stimulus method, ability to compare multiple items at the same time.

Disadvantages:  requires student to scan multiple items on table (and instructor to manipulate multiple items during assessment), may be difficult to determine a preferred and non preferred selection criteria.

 

Details Regarding Multiple Stimulus With Replacement Assessments in Catalyst

Stimulus Array:  All stimuli being assessed are presented each trial.  After each trial, the stimulus selected is replaced and the item on the far right is moved to the first position on the left and all other items shift to the right.

Scoring/Results:  Results are presented as percentage of times the item was selected (# of times the item was selected / # of times the item was presented X 100).  The number of trials during the assessment is determined by the number of stimulus items being assessed (e.g., if 5 items are being assessed, the assessment will contain 5 trials).

Termination Criteria:  The session is terminated when all trials are completed or if no item is selected during a trial.


Details Regarding Multiple Stimulus Without Replacement Assessments in Catalyst

Stimulus Array:  All stimulus items are presented during the first trial of the assessment.  After an item is selected, the item is NOT replaced so the stimulus array decreases by one.  After each trial the stimulus on the far right is moved to the first position on the left and all other items shift to the right.

Scoring/Results:  Results are presented as point values.  The first item selected is given the max value.  Max value is determined by the number of items being assessed.  For example if 8 items are being assessed, then the max point value is 8.  The second item selected is scored as 7 points and so forth.  The number of trials during the assessment is determined by the number of stimulus items being assessed (e.g., if 8 items are being assessed, the assessment will contain 8 trials).

Termination Criteria:  The session is terminated when all items have been selected or no item is selected.




GENERAL CONSIDERATIONS FOR SPAs

  • Collect anecdotal information from caregivers and/or teaching staff about stimulus preferences.
  • Allow individual to sample a variety of stimuli (including stimuli identified by familiar caregivers and/or staff) prior to assessment.
  • Select assessment stimuli based on direct observation(s).
  • Gather materials and prepare to present stimuli during preference assessment “sessions.”
  • Typically, edible stimuli should be assessed separately from other potential preferences, such as items or activities.
  • Preferences should be assessed early in the development of treatment procedures and often throughout intervention—often daily.
  • Measure individual’s response(s) to presented stimuli.
  • Preferences change over time, so vary the stimuli included in assessments.

 

 



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