Researcher:
Gürdere, Ceren

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PhD Student

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Ceren

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Gürdere

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Gürdere, Ceren

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2018 - 20192

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Researcher Of Publications: search.filters.isAuthorOfPublication.2a82bb96-9771-4a28-8da0-5454710e15f1

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    Eyewitness memory distortion following co-witness discussion: a replication of Garry, French, Kinzett, and Mori (2008) in ten countries
    (AMER PSYCHOLOGICAL ASSOC, 2019) Ito, Hiroshi; Barzykowski, Krystian; Grzesik, Magdalena; Janssen, Steve M. J.; Khor, Jessie; Rowthorn, Harriet; Wade, Kimberley A.; Luna, Karlos; Albuquerque, Pedro B.; Kumar, Devvarta; Singh, Arman Deep; Cecconello, William Weber; Cadavid, Sara; Laird, Nicole C.; Baldassari, Mario J.; Lindsay, D. Stephen; Mori, Kazuo; Department of Psychology; N/A; Gülgöz, Sami; Gürdere, Ceren; Faculty Member; PhD Student; Department of Psychology; N/A; College of Social Sciences and Humanities; Graduate School of Social Sciences and Humanities; N/A; 49200; N/A
    We examined the replicability of the co-witness suggestibility effect originally reported by Garry et al. (2008) by testing participants from 10 countries (Brazil, Canada, Colombia, India, Japan, Malaysia, Poland, Portugal, Turkey, and the United Kingdom; total N=486). Pairs of participants sat beside each other, viewing different versions of the same movie while believing that they viewed the same version. Later, participant pairs answered questions collaboratively, which guided them to discuss conflicting details. Finally, participants took a recognition test individually. Each of the 10 samples replicated the Garry et al. finding: Participants often reported on the final test a non-witnessed answer that their co-witness had stated during the collaboration phase. Such co-witness suggestibility errors were especially likely when the witness had not disputed the co-witness's report during the collaboration phase. The results demonstrate the replicability and generalizability of the co-witness suggestibility effect.
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    PublicationOpen Access
    Differential bilateral primary motor cortex tDCS fails to modulate choice bias and readiness in perceptual decision making
    (Frontiers, 2018) Çakmak, Yusuf O.; Department of Psychology; Türkakın, Esin; Akbıyık, Seda; Akyol, Bihter; Gürdere, Ceren; Balcı, Fuat; Teaching Faculty; PhD Student; Faculty Member; Department of Psychology; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Social Sciences and Humanities; Graduate School of Social Sciences and Humanities; N/A; N/A; N/A; N/A; 51269
    One of the critical factors that guide choice behavior is the prior bias of the decisionmaker with respect to different options, namely, the relative readiness by which the decision-maker opts for a specific choice. Although previous neuroimaging work has shown decision bias related activity in the orbitofrontal cortex, intraparietal sulcus (IPS) and dorsolateral prefrontal cortex, in a recent work by Javadi et al. (2015), primary motor cortex was also implicated. By applying transcranial direct current stimulation (tDCS), they have revealed a causal role of the primary motor cortex excitability in the induction of response time (RT) differences and decision bias in the form of choice probability. The current study aimed to replicate these recent findings with an experimental design that contained a sham group to increase experimental control and an additional testing phase to investigate the possible after-effects of tDCS. The conventional decision outputs such as choice proportion and RT were analyzed along with the theorydriven estimates of choice bias and non-decision related components of RTs (e. g., motor implementation speed of choices made). None of the statistical comparisons favored the alternative hypotheses over the null hypotheses. Consequently, previous findings regarding the effect of primary motor cortex excitability on choice bias and response times could not be replicated with a more controlled experimental design that is recommended for tDCS studies (Horvath et al., 2015). This empirical discrepancy between the two studies adds to the evidence demonstrating inconsistent effects of tDCS in establishing causal relationships between cortical excitability and motor behavior.