A non-concurrent multiple-baseline across participants design was employed (Barlow and Hersen
). Systematically staggered baseline sessions were conducted 1 day per week for approximately 4 h per day for 9–28 weeks, followed by 6–10 weeks of intervention where individualized orienting cues were presented. A manualized PRT intervention (Koegel et al.
) was implemented, during both baseline and intervention. The only difference between the conditions was that during intervention an individualized orienting cue was provided to evoke attention prior to presenting a verbal prompt for expressive communication.
During baseline a standard intervention without a specific orienting cue was implemented according to the procedures described for PRT (Koegel et al.
; Koegel and Koegel
). Specifically, a trial began when the interventionist selected an object/activity in which the child appeared interested. Then the interventionist created an opportunity for expressive word use by verbally modeling a single word for the item/activity. For example, when a child showed interest in a toy, either by looking at or reaching for the item, the interventionist verbally prompted the child to name the object (e.g., “train”). The item was provided to the child contingent upon a word attempt or correct expressive label. This general procedure was repeated with a variety of child-preferred items and activities, several times per minute. In addition, systematic opportunities for unprompted responses were provided throughout the sessions by holding up an object and providing an opportunity for the child to independently label it.
Intervention Condition—Individualized Orienting Cue
During the intervention condition, all procedures were the same as in baseline, except the interventionist provided an individualized orienting cue at the start of each trial. Each orienting cue was presented immediately (less than 1 s) prior to presenting a verbal model. To identify the orienting cue, a variety of stimuli were presented until the child: (a) oriented to the clinician; and (b) engaged in the activity related to the targeted stimulus. Identifying an orienting cue typically took less than 2 h, and is described below.
For Zane, the first attempt to provide an orienting cue using modeled motor actions (e.g., making a circular motion with both hands, similar to a wheel going around and around, when providing the verbal model “car”) did not result in any consistent orienting. Therefore, a second attempt to provide an orienting cue was initiated, using a “high-five” gesture. This stimulus consistently produced an orienting response from Zane, with him looking directly at the clinician and slapping her hand in a “high five” gesture, and, therefore, was provided as an orienting cue immediately prior to presenting a verbal model during intervention.
For Parker, a combination of modeled motor actions and high-fives provided jointly with verbal models were the first attempts to produce an orienting response. However, as they did not produce an orienting response from Parker, a third attempt was made to provide an orienting cue by presenting novel stimuli such as hugs, kisses, tickles, and novel sounds. Such activities consistently produced orienting responses. Thus, novel actions were employed as orienting cues immediately prior to presenting verbal models during intervention.
For Alex, the first attempt at identifying an orienting cue, involving a modeled motor action presented simultaneously with a verbal model, effectively and consistently produced an orienting response. Therefore, an antecedent stimulus for motor imitation was provided immediately preceding the presentation of a verbal model throughout intervention.