The present study examines whether middle-aged adults' memories are more integrated which may reduce the interference induced by the accumulation of memory traces. This better integration may also be associated with reduced memory discrimination performance. Middle-aged adults were targeted as this population could be at the right time where there is a significant growth of knowledge over age without being subject to age-related memory decline. This choice is particularly relevant as there is very few studies targeting this population.

The methodology relies, on the one hand, on memory integration, as assessed by the Associative Inference Task (AIT), and on memory discrimination, as assessed by the Mnemonic Similarity Task (MST), on the other hand. In addition, vocabulary, verbal fluency and processing speed are also taken into account.

I found the topic timely and the study to be of a very good quality. The methodology is overall very clean and well defined as the statistical analyses. The results could significantly contribute to the field and open new research questions to be explored.

My main concerns are essentially on a theoretical side. First of all, the construct of integration, which is central to this study, should be better defined. The authors claim that memory integration is essential to episodic memory, which is true, but the meaning chosen for the study could be more related to semantic knowledge. Indeed (episodic) memory integration is often understood as “binding” (e.g. Opitz, 2010) or “unitization” (e.g. D’Angelo et al., 2017), whereas the integration of multiple traces could also be defined as a generalization principle (see Kumaran & McClelland, 2012 with the AIT) and as such be related to semantic knowledge (see Versace et al., 2014). I think that the paper will gain in clarity if the definition of integration, as proposed l.81 and after, is also contrasted with the other forms of memory integration. The issue is of particular relevance also for the results. I would have hypothesized that memory discrimination should be related to episodic binding (see Kent et al., 2016) rather than memory integration over multiple traces especially in aging (see Mille et al., 2021)(see also Brunec et al., 2020). Could the authors develop their point of view regarding this last point (at least in the response to this comment)?

A second theoretical question regards the associative-deficit hypothesis in aging developed by Naveh-Benjamin (see Naveh-Benjamin & Mayr, 2018). According to this hypothesis, normal cognitive aging is marked by an associative deficit. I would appreciate if the authors could discuss their results in the light of this hypothesis since the AIT requires to associate different stimuli.

Finally, I was very surprised to see the Fribbles used to assess processing speed. According to my knowledge, it would better be described as a visual discrimination task (Barense, Gaffan, & Graham, 2007; 10.1016/j.neuropsychologia.2007.05.023). This should be at least mentioned in the discussion. Moreover, when considering the representational-hierarchical model (see Kent et al., 2016), one might expect that the Fribbles discrimination task predicts memory discrimination (as assessed here by the MST). It would be very interesting to conduct such an analyze (I would predict that fribbles’ performance predicts MST performance even over other processing speed index).

Minor points: • The authors conclude that there is no better integration in middle-aged adults. However, generalization processes can also occur in the long-term, especially during sleep (Tompary & Davachi, 2017; doi: 10.1016/j.neuron.2017.09.005). This might be addressed as a limit or a perspective of the present study. • It is not clear to me if the reaction’s times were used only for the correct responses or not. • Page 12: this long paragraph should be split into multiple ones. • Could it be possible to present the raw data of the AIT? • Please, specify the order of the tasks • Would it possible to add the AIT index computation as equations rather than only text description? • Please thank for specifying that z-scores are used/reported in the tables’ caption or note. • Line 42: I think that a word (“by” ?) is missing “...be explained increased…” • Line 351: a space is missing between "descriptive)." and "In a similar fashion". • Line 614 and 699: the author’s first name should be presented after his last name • Line 730 and 740: this reference (Schaie vs Shaie) is in duplicate.

References • Brunec, I. K., Robin, J., Olsen, R. K., Moscovitch, M., & Barense, M. D. (2020). Integration and differentiation of hippocampal memory traces. Neuroscience & Biobehavioral Reviews. • D’Angelo, M. C., Noly-Gandon, A., Kacollja, A., Barense, M. D., & Ryan, J. D. (2017). Breaking down unitization: Is the whole greater than the sum of its parts?. Memory & cognition, 45(8), 1306-1318. • Kent, B. A., Hvoslef-Eide, M., Saksida, L. M., & Bussey, T. J. (2016). The representational–hierarchical view of pattern separation: Not just hippocampus, not just space, not just memory?. Neurobiology of Learning and Memory, 129, 99-106. • Kumaran, D., & McClelland, J. L. (2012). Generalization through the recurrent interaction of episodic memories: a model of the hippocampal system. Psychological Review, 119(3), 573. • Naveh-Benjamin, M., & Mayr, U. (2018). Age-related differences in associative memory: Empirical evidence and theoretical perspectives. Psychology and Aging, 33(1), 1. • Mille, J., Brambati, S. M., Izaute, M., & Vallet, G. T. (2021). Low-Resolution Neurocognitive Aging and Cognition : An Embodied Perspective. Frontiers in Systems Neuroscience, 15, 687393. • Opitz, B. (2010). Neural binding mechanisms in learning and memory. Neuroscience & Biobehavioral Reviews, 34(7), 1036–1046. https://doi.org/10.1016/j.neubiorev.2009.11.001 • Versace, R., Vallet, G. T., Riou, B., M, L., Labeye, E., & Brunel, L. (2014). ACT-IN: an integrated view of memory mechanisms. Journal of Cognitive Psychology, 26(3), 280–306.