A fundamental goal of Information Retrieval (IR) is to satisfy search/ers' information need (IN). Advances in neuroimaging technologies have allowed for interdisciplinary research to investigate the brain activity associated with the realisation of IN. While these studies have been informative, they were not able to capture the cognitive processes underlying the realisation of IN and the interplay between them with a high temporal resolution. This paper aims to investigate this research question by inferring the variability of brain activity based on the contrast of a state of IN with the two other (no-IN) scenarios. To do so, we employed Electroencephalography (EEG) and constructed an Event-Related Potentials (ERP) analysis of the brain signals captured while participants experiencing a realisation of IN. In particular, the brain signals of 24 healthy participants were captured while performing a Question-Answering (Q/A) Task. Our results show a link between the early stages of processing, corresponding to awareness and the late activity, meaning memory control mechanisms. Our findings also show that participants exhibited early N1-P2 complex indexing awareness processes and indicate, thus, that the realisation of IN is manifested in the brain before it reaches the user's consciousness. This research contributes novel insights into a better understanding of IN and informs the design of IR systems to better satisfy it.

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The searcher's realisation of Information Need (IN) in Information Retrieval (IR) is triggered by a perception of the knowledge gap the searcher perceives. Introspective epistemic (knowledge) feelings are evoked, describing the state of the user's anomaly. For instance, Feeling-of-Knowing (FOK) refers to a state of a user's temporary unavailability to recall the information in question. The role and the extent to which such epistemic feelings inform the user's cognitive context need further research. Our methodological design followed the Recall-Judgment-Recognition (RJR) paradigm, commonly used as a framework for memory tests. We collected behavioural data from twenty-four participants in a general knowledge Q/A user study to investigate the interplay of users' internal perceptions of knowing based on three metacognitive states (Recall). The results showed significant differences across different metacognitive states and subsequent memory retrieval performance (Recognition), leading to our conclusion of the accuracy of the metacognitive states of knowing. Specifically, we found that FOK was only a relatively accurate predictor of MR. The amount of failures of recognition connected to FOK, thus, suggests that the participants might have misattributed their positive FOK. Participants could not recognise the answer as they thought, giving rise to phenomena such as Illusion of Knowing. Furthermore, our data support the significant effect of task (question) difficulty on participants' metacognitive states. Based on the interactions between Recall and Recognition, our results contribute to the understanding of the graded nature of cognitive functions, supporting the user's cognitive context in information search and expanding such an area to the realm of contextual task difficulty.