1. How is the research question operationalized? (First, identify the abstract constructs being studied. Next identify the concrete way these are being observed or measured. This should include your IV and DV.)

RESEARCH ARTICLE

METHODParticipants

Erin, Carl, and Mike were 10, 8, and 7 years old, respectively. All had a diagnosis of autism, had been receiving behavior-analytic services for at least 5 years, could imitate vocalizations, had previous exposure to 0-s prompt-delay procedures to learn tacts, and were primarily engaged in instruction that provided the manipulation of quality as a differential reinforcement contingency (e.g., praise and edible items for unprompted correct responses, praise for prompted correct responses). Additional participant information is available from the second author.

Setting and Materials

All sessions were conducted at a desk in the participants' learning areas in a school that provided behaviorally based educational services. A video camera recorded some sessions for purposes of collecting data on interobserver agreement and treatment integrity.

Five or 10 unknown tacts (e.g., pictures of food, vehicles, and animals) were identified for each condition (procedures for identifying unknown images are available from the second author). During the treatment conditions, each picture was affixed to one of four colored pieces of paper (associated with a specific treatment condition), placed in a page protector, and presented in a three-ring binder. In addition, a matching colored sheet of paper in a clear page protector was placed on top of each picture to prevent participants from viewing the picture before the experimenter's instruction to label the picture.

Dependent Variables and Interobserver Agreement

The experimenter scored correct unprompted, incorrect unprompted, correct prompted, and incorrect prompted responses on data sheets. A correct unprompted response was defined as the participant emitting the correct tact before the delivery of the prompt. Only correct unprompted responses were included in the session data. Other response definitions are available from second author.

A second independent observer scored a minimum of 34% of baseline and treatment sessions across all participants. Trial-by-trial interobserver agreement was calculated by dividing the number of agreements by the number of agreements plus disagreements and converting the result to a percentage. The mean agreement scores were 100% for Erin, 98% (range, 90% to 100%) for Carl, and 99% (range, 90% to 100%) for Mike.

Preference Assessments

We conducted separate paired-stimulus preference assessments (Fisher et al., 1992) to identify the edible items and colors (to be assigned as condition-correlated stimuli) to be used during the reinforcement evaluations and the treatment comparisons. A single-trial multiple-stimulus-without-replacement preference assessment was conducted before each reinforcer evaluation and treatment session using the top four or five items identified from the preference assessment. The first item selected was used during the subsequent reinforcer assessment or treatment session.

Edible Amount and Edible Size Assessments

An assessment was conducted to determine the number of pieces of an edible item (hereafter referred to as edible amount) to be delivered for correct unprompted responses during the quality, magnitude, and nondifferential conditions and following correct prompted responses during the nondifferential condition. On each trial of the assessment, the experimenter placed a large number of pieces of an edible item in a closed container (e.g., 50 Skittles) and presented the instruction, "You can open the box and eat the [edible item] if you want." The participant had a 5-min free access period for each of his or her top four or five edible items identified in the preference assessment. The number of pieces of an edible item consumed was counted and divided by the number of trials in a session (i.e., 20). If the total number of items consumed was not divisible by 20, the value was rounded to the nearest whole number. The edible amount identified (e.g., two Skittles) was then used in the reinforcer evaluations and treatment conditions.

We conducted an assessment to determine the size of the edible item that was provided after correct prompted responses during the magnitude condition (hereafter referred to as small edible). Rather than arbitrarily selecting this small magnitude value, we chose to identify the smallest size of an item that the participant would continue to respond to consume in order to maximize the difference between magnitude values. The experimenter placed a single piece of an item in a closed container and presented the instruction, "You can open the box and eat the [edible item] if you want." If the participant opened the container and consumed the item, it was reduced in size by 50%, and another trial was initiated. The assessment was terminated if the participant did not open the container to consume the item within 30s of the experimenter's instruction or if the participant consumed the item when it was one eighth of the original size. This was repeated for each participant's top four or five edible items identified in the preference assessment.

Reinforcer Evaluations

Each participant completed three progressive-ratio reinforcer evaluations (Roane, Lerman, & Vorndran, 2001): praise versus no consequences, praise versus the edible amount and praise, and small edible and praise versus the edible amount and praise. An arbitrary response was selected for each participant to complete. Procedural details are available from the second author.

Design and General Procedure

An adapted alternating treatments design (Sindelar, Rosenberg, & Wilson, 1985) was used. Sessions consisted of 20 trials, and one session per experimental condition was conducted per day, 1 to 5 days per week, with a minimum of 5min between each condition. Session order was determined randomly without replacement. Each target was presented equally as often within a session and was not presented on more than two consecutive trials, and the order of targets was rearranged each session. A different color was associated with each condition, and the participant had to touch each colored binder before each session. A progressive prompt-delay procedure was implemented (details can be obtained from the second author). The experimenter provided a model prompt following incorrect unprompted responses and initiated the next trial if the participant did not respond correctly to the prompt. Teaching for all targets continued until participants demonstrated correct unprompted responding at or above 90% for two consecutive sessions.

Baseline

When the picture was in view, the experimenter said, "What is this?" The participant had 5s to respond. The experimenter did not provide feedback for correct or incorrect responses.

Quality

After the participant touched the colored binder associated with the quality condition, the experimenter presented the instruction to label the picture. During the two sessions with trials conducted with a 0-s prompt delay, the experimenter provided praise and the edible amount after each correct prompted response. During sessions that involved trials conducted with a 1s or longer prompt delay, the experimenter provided the predetermined edible amount (as identified in the edible amount assessment) and praise after each correct unprompted response and provided praise only after a correct prompted response.

Magnitude

Sessions were identical to those in the quality manipulation except the experimenter provided the predetermined edible amount and praise after correct unprompted responses and the small edible item (as determined in the edible size assessment) and praise after correct prompted responses.

Nondifferential reinforcement

These sessions were the same as above, except the experimenter provided the predetermined edible amount and praise after both correct unprompted and prompted responses.

Control

As in baseline, during these sessions, prompts and reinforcers were not provided.