Table 2 Framework sub-components

 Attention

The distinct and resource-dependent channels to generate initial attention of the target group via distinct access levels (individual, organisation, public) and access contents (e.g. study topic vs. study process).

“I read your ad on Facebook and am very interested. I also meet all the criteria. If you are still looking for participants, I would be very happy to hear from you!” (S9)

 Interest: Gratification-oriented

Financial interest proved to be important especially for people with lower socioeconomic status. Elsewere content and support oriented interests were decisive.

“Unexpectedly, I learned a lot (…). So I will be able to take away more from this survey than the allowance. Thank you very much!” (S72)

 Appraisal of the appropriateness of the effort

The eventual judgment potential participants make to decide whether to join the study, which depends particularly on the relation, i.e. balance between required effort (e.g. time, organizing childcare) and expected outcome, i.e. personal benefit.

“As I come from XX, attending for only 3 h would be too time-consuming for me (…). The cost-benefit factor does not make sense for me. Perhaps digital participation would be possible if you made it a hybrid event.” (S111)

 Coping / managing self-efficacy

The internal consideration process in which participants estimate, appraise their own abilities for successful participation and whether strategies (skills) are available to handle expected or unexpected problems.

“I would very much like to participate in your project. However, I am still fully breastfeeding and am not sure if it is feasible with the baby in October (from XX district). Would the baby be able to be at the meeting? Otherwise I would be very happy to be there outside the meeting.” (S141)

 Maintenance motivation

Three foci: thematic-content, supportive and gratification-oriented. Maintenance motivation is more pronounced in the actional phase, as it involves actual participation experiences at this point.

“Basically, after the first interview I already found it difficult to motivate myself for the next one. The feeling became stronger during the second interview. The connection to the topic was missing, I didn’t see any sense (…).” (S217)

 Continuing decision

A participants’ decision to continue with follow-up assessments after initial evaluation considerations. Reasons for early dropout vary, but often relate to time constraints.

“I’ll ask my husband again (…), but due to the shortage of time at the moment - I’m guessing he won’t be able to make it.” (S227)

 Barriers and support factors

The specific factors that narrow down an individuals’ chances to decide in favor of study participation, and that differ according to each framework phase, e.g. missing technological resources during concrete participation planning (intentional phase) or a lack of time to participate in subsequent phases/assessments as part of the initial study (actional phase), which require development of action steps to create ‘support factors’, e.g. strong content-wise links of the study with the interests of (potential) participants.

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