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CHAPTER 5 136 these two phases as a similar context (context A; signaling [potential] danger). Participants may have perceived the Extinction phase as a different context (context B; signaling safety), because A and C were no longer followed by the US, and safety behavior was not available. The reintroduction of safety behavior availability for C in the Return of safety behavior phase may have given participants the impression that they had returned to context A. This may explain why threat expectancy for A and B initially increased in the Return of safety behavior phase. Our data do not show whether threat expectancy increased for C, because all participants used safety behavior on all C*- trials. However, this safety behavior use may have been motivated by increased threat expectancy for C. Threat expectancy for A and B re- extinguished during the Return of safety behavior phase. However, using safety behavior during C*- trials may have prevented this for C (i.e., protection from re- extinction), which may explain the relatively high threat expectancy for C in the Test phase. To recapitulate, reintroducing safety behavior availability after fear extinction may have triggered a return of threat expectancy, which was protected from re- extinction for C by safety behavior use. It remains unclear whether the return of threat expectancy was caused by the availability or use of safety behavior, or by both. To investigate the direct threat signaling properties of safety behavior availability, future studies could assess whether safety behavior availability (i.e., the green plug) alone (i.e., without simultaneous CS presentation) increases threat expectancy. If that is the case, then the inclusion of extinction trials in which the green plug is present (but the use of safety behavior is prevented) might extinguish the potential threat signaling properties of safety behavior availability. Vervliet and Indekeu (2015), however, found that using a visual cue to indicate safety behavior (un)availability, and verbally instructing participants about the (un)availability of the safety behavior response resulted in comparable returns of safety behavior use after fear extinction. This suggests that safety behavior’s resistance to fear extinction cannot be attributed