The purpose of this study was to extend the literature on secondary target and auditory tact training by teaching children with ASD to tact safety sounds and their function through secondary target procedures (Bergmann et al., 2023; Dass et al., 2018; Delmolino et al., 2013; Hanney et al., 2019; Loughery et al., 2014). We presented secondary targets during the consequence portion of learning trials in two teaching arrangements. These results suggest that including secondary targets in the consequence portion of the learning trials was efficacious for both participants, in teaching the function of auditory stimuli. These results replicate previous findings (e.g., Dass et al., 2018; Loughery et al., 2014; Reichow & Wolery, 2011) by demonstrating that the inclusion of secondary targets is an effective teaching arrangement for teaching information about stimuli, specifically non-visual stimuli (Dass et al., 2018). To our knowledge, this is the first paper to teach the function of auditory stimuli through secondary target procedures.

Moreso, we compared two different teaching arrangements when presenting the auditory stimulus. Although both conditions were effective for teaching auditory tacts and the function of auditory stimuli for both participants, primary and secondary targets were acquired in fewer sessions during Condition 1-Single Presentation. This was consistent across both the initial and replication treatment comparisons, with one exception. Michael acquired the secondary targets in fewer sessions in Condition 2-Re-presentation, during his initial treatment comparison. Additionally, total training time was less for Condition 1-Single Presentation during both treatment comparisons for both participants. Overall findings suggest that the teaching arrangement used in Condition 1-Single Presentation may result in more efficient learning. However, because we only evaluated efficiency using total training time and sessions to mastery, we cannot say for certain that one condition resulted in more efficient outcomes. Future research should continue to investigate alternate means of measuring efficiency (e.g., mean training time per mastered target) to draw these conclusions. Furthermore, because this is the first study to date that has evaluated using secondary target instruction to teach the function of auditory stimuli, additional research is needed to replicate the findings and determine whether the re-presentation of the auditory stimulus is necessary during training.

This study contributes to the scant research literature on auditory tact training with individuals with ASD (Bergmann et al., 2023; Hanney et al., 2019) by suggesting that an isolated stimulus-presentation arrangement (e.g., an auditory stimulus presented without any visual stimuli) may be effective in teaching auditory stimulus tacts. Although both participants demonstrated strong echoic repertoires as indicated by their VB-MAPP® scores, neither participant vocally echoed the experimenter’s presentation of the secondary targets during training sessions. The results of the present study demonstrated that both participants learned the secondary targets in the absence of overt echoic behavior after the secondary targets were presented. These findings differ from previous research on secondary target procedures (Nottingham et al., 2017; Vladescu & Kodak, 2013) by suggesting that overt echoics may not be a necessary component to acquire secondary targets.

One explanation for the lack of overt echoic behavior could be that the participants engaged in covert bi-directional naming (BiN; Horne & Lowe, 1996; Miguel, 2016; 2018). Bi-directional naming occurs when a child responds, either overtly or covertly, to a stimulus as both a speaker and a listener when only one relation has been trained (Miguel & Petursdottir, 2009). In this case, participants may have initially acquired the secondary target phrase by listening to the experimenter during treatment sessions and emitting covert echoics as a speaker. Then, when the auditory stimulus was played during the secondary target probes the participant may have tacted the stimulus name covertly as a speaker (e.g., “whistle”) then emitted the secondary target (e.g., “that means look at the lifeguard”) under intraverbal control. We cannot say with certainty that covert BiN may be the behavioral mechanism responsible for the acquisition of the secondary target responses, though the current literature on instructive feedback continues to incorporate discussions of the role of BiN in their conceptual analysis of results (Frampton & Shillingsburg, 2020; Tullis et al., 2017, 2020, 2022). Future research should explore ways to evaluate the role that covert echoic behavior and BiN have in acquisition of secondary targets. One way to do this may be to conduct a BiN assessment prior to experimental conditions to assess the participants’ naming repertoire and the influence the skill may have on acquisition (e.g., Gavidia et al., 2022; Kobari-Wright & Miguel, 2014, Miguel, 2018).

During secondary target probes in the initial comparison, both participants often responded to the discriminative stimulus, “What does this sound mean?” with the primary target response, demonstrating a consistent error pattern. Similar responding errors were observed in Loughrey et al. (2014), in which the participants vocalized the stimulus name (e.g., “squash”) rather than the category name (e.g., “vegetable”). When this error occurred, the experimenters acknowledged the response and presented the modified verbal stimulus to combat this error (Loughrey et al., 2014). In the present study, the experimenter included a supplemental verbal stimulus, beginning at probe session #23 for Michael and probe session #20 for Sal. If the participant responded with the primary target response (e.g., when a crosswalk sound was played and the experimenter asked, “What does this sound mean?” the participant responded, “Crosswalk”), the experimenter responded by confirming and re-stating the discriminative stimulus, (e.g., saying, “It is a crosswalk. What does it mean?”). These error patterns may suggest faulty stimulus control by all aspects of the relevant antecedent stimuli (Loughrey et al., 2014). Participant responses may not have been under conditional control and were rather multiply controlled by the verbal antecedents and auditory stimuli (Axe, 2008; Gavidia et al., 2022). Future research should evaluate the similarity between the discriminative stimulus when teaching primary and secondary targets and the influence that has on the acquisition of targets in each condition.

This study is not without limitations. As the number of safety sounds recruited from the environment was not limitless, we were only able to assign two stimuli to each condition without reserving additional stimuli for generalization. Future researchers should program for response generalization by training across decibels, locations, or multiple exemplars of target auditory stimuli. Responding to variations of these stimuli is critical as, for instance, different exemplars of smoke alarms may be sounded across differing environments.

A second limitation of the current study was the use of target assignment across experimental and control conditions without equating the number of syllables in primary or secondary target responses. This resulted in instances where the primary or secondary targets for control conditions contained more syllables compared to teaching sets which may have resulted in more effortful responses. It is important to note that the difference in syllables per set was no more than three (ranging from 1–3), and the condition containing the greatest number of syllables per set differed between the initial and replication comparisons. In addition, control targets from the initial comparison were later integrated into a teaching condition during the replication comparison and were later acquired by both participants. This finding suggests that control targets were no more or less difficult than targets included in teaching conditions.

As a final point, we did not measure whether the participants would engage in the safety action described in the function statement (e.g., leaving the building in the presence of a fire alarm). It is crucial that individuals not only identify a safety sound and recognize the action that is associated with that sound but also engage in that safety response, as these skills may prevent accidents or even death. Future researchers should measure whether participants are able to engage in the action when faced with these safety sounds in real-life scenarios.

As the number of injuries and deaths of individuals with ASD is reported to be higher than those individuals without ASD (National Autism Association, n.d.), it is the responsibility of researchers to evaluate interventions that may assist in teaching these individuals the skill repertoires to remain safe in their environment. Ultimately, learning how to avoid danger is a socially valid treatment goal that will lead to increased independence and safety in the individuals’ community.