Response: Commentary: Pupil old/new effects reflect stimulus encoding and decoding in short-term memory

Citation: Brocher A and Graf T (2017) Response: Commentary: Pupil old/new effects reflect stimulus encoding and decoding in short-term memory. Research on recognition memory has a long tradition in ERPs (see Yonelinas, 2002; Vilberg and Rugg, 2008 for reviews). One assumption is that recognition memory involves two distinct processes: familiarity and recollection. Familiarity refers to the feeling that a presented stimulus has been studied before, while recollection involves somewhat conscious retrieval of information associated with the respective study episode. Recently, Kafkas and Montaldi (2011, 2012) suggested that familiarity and recollection could also be distinguished in the size of the pupil. The claim is that the pupil dilates more for recollected than familiar stimuli. The distinction between familiarity and recollection in pupil size, however, is entirely based on remember/know paradigms. In Kafkas and Montaldi (2012), participants judged whether a presented stimulus was " old " or " new " and, in case of an " old " response, whether they can retrieve specific information of the study episode (" recall " response) or not (" familiar " response), and, in case of a " familiar " response, they then estimated the degree of familiarity (" weak " or " moderate " or " strong "). In Brocher and Graf (2016), we argued that using a remember/know procedure is not ideal to unambiguously establish that pupil size distinguishes familiarity and recollection because it is difficult to estimate what exactly drives larger pupils in " remember " than " familiar " responses. It is possible that the observed differences obtain because participants engage in different processes after they made a response. Kafkas and Montaldi (2012) note that participants are " carefully trained to discriminate between instances of familiarity and recollection " (p. 3082). This means that participants are presumably highly sensitive to that discrimination and aware of the fact that it is crucial to their task. This point is important as it raises the possibility that, after pressing " recall, " participants engage in effortful retrieval to be sure that their response was correct. This could lead to larger pupils in " recollection " than " familiarity " responses (cf. Granholm et al., 1996; Granholm and Steinhauer, 2004). In Brocher and Graf (2016), we conducted five pupil old/new experiments with materials that differently affect familiarity and recollection processes in ERPs. In all experiments, we used a simple old/new judgment task. Considering the well-established—albeit …