Recent proposals have attributed a key role to novelty in the formation of new episodic memories. These proposals are based on evidence of enhanced memory and greater metabolic activity in the hippocampus in response to novel relative to familiar materials. However, such novelty effects are incongruous with long-standing observations that familiar items and lists are associated with better memory than novel ones. In four experiments, I explored possible reasons for this apparent discrepancy. In Experiment 1, I directly tested whether previously observed novelty effects were the result of novelty, discrimination demands, or both. I used linguistic materials (proverbs) to replicate the novelty effect but found it occurred only when familiar items were subject to source confusion. In Experiment 2, to examine better how novelty influences episodic memory, I used experimentally familiar, pre-experimentally familiar, and novel proverbs in a paradigm designed to overcome discrimination demand confounds. Memory was better for both types of familiar proverbs. These cognitive results indicate that familiarity, not novelty, leads to better episodic memory for studied items, regardless of whether familiarity is experimentally induced or based on prior knowledge. I also conducted two fMRI experiments to evaluate the neural correlates of the encoding of novel and familiar forms of information. In Experiment 3, I compared the neural encoding correlates of source memory for novel and familiar visual scenes using fMRI. Replicating previous neuroimaging studies, I observed an anterior novelty-sensitive region of the hippocampus specialized in novelty encoding. Unlike past studies, I also probed for familiarity-encoding regions and identified such regions in the posterior hippocampus. I replicated this pattern in Experiment 4 using proverbs as stimuli. As in Experiment 2, I found the effect held whether familiarity was based on prior knowledge or experimental induction. In both fMRI experiments, anterior and posterior hippocampal regions were functionally connected with different large-scale networks, helping to explain local variation in hippocampal functional specialization in terms of different neural contexts. Together, these experiments show that stimulus familiarity enhances episodic memory for materials, and that novelty is processed differently, not preferentially, in the hippocampus. A new model of hippocampal novelty processing is proposed.

The aim of this study is to investigate whether blind individuals display cognitive advantages over sighted individuals with regard to second language acquisition. Previous studies from neuropsychology have indicated that this is the case. It has been found that blind L1 speakers can compensate for loss of vision by developing better perceptual and cognitive skills compared to sighted individuals, skills that are highly relevant to language acquisition. These studies do not, however, investigate blind L2 speakers, for whom it is not clear whether these advantages are also found.  In all, 80 adults participated in the study: 40 L2 speakers of Swedish (11 early blind, 9 late blind, 20 sighted, AO<18) and a matching group and subgroups of L1 speakers. These speakers underwent tests on speech perception in noise, accentedness in an L2 and memory functions. The results revealed that L2 speakers are at a great disadvantage perceiving speech in noise compared to L1 speakers, and that there was no advantage associated with blindness. In the L1 speakers group, however, the results revealed that the early blind had advantages compared to the late blind and sighted in white noise, but that both blind groups were more negatively affected by babble noise than the sighted. The results in relation to accentedness in an L2 revealed that there were no advantages associated with blindness. The results further revealed there were no advantages associated with blindness on the episodic memory test. The results did, however, reveal that the early blind performed significantly better than the late blind and sighted on all phonological short-term memory tests and that both the early and late blind were significantly better than the sighted on recognition memory for new words, irrespective of language background. The conclusion is that blindness is associated with advantages in, for example, ability to learn new words and syntax, acquisition rate, ultimate L2 attainment, and language aptitude.

La présente thèse examine les liens entre le sommeil, la mémoire épisodique et les rêves. Dans une première étude, nous utilisons les technologies de la réalité virtuelle (RV) en liaison avec un paradigme de privation de sommeil paradoxal et de collecte de rêve en vue d'examiner l'hypothèse que le sommeil paradoxal et le rêve sont impliqués dans la consolidation de la mémoire épisodique. Le sommeil paradoxal a été associé au rappel des aspects spatiaux des éléments émotionnels de la tâche RV. De la même façon, l'incorporation de la tâche RV dans les rêves a été associée au rappel des aspects spatiaux de la tâche. De plus, le rappel des aspects factuels et perceptuels de la mémoire épisodique, formé lors de la tâche VR, a été associé au sommeil aux ondes lentes. Une deuxième étude examine l'hypothèse selon laquelle une fonction possible du rêve pourrait être de créer de nouvelles associations entre les éléments de divers souvenirs épisodiques. Un participant a été réveillé 43 fois lors de l'endormissement pour fournir des rapports détaillés de rêves. Les résultats suggèrent qu'un seul rêve peut comporter, dans un même contexte spatiotemporel, divers éléments appartenant aux multiples souvenirs épisodiques. Une troisième étude aborde la question de la cognition lors du sommeil paradoxal, notamment comment les aspects bizarres des rêves, qui sont formés grâce aux nouvelles combinaisons d'éléments de la mémoire épisodique, sont perçus par le rêveur. Les résultats démontrent une dissociation dans les capacités cognitives en sommeil paradoxal caractérisée par un déficit sélectif dans l'appréciation des éléments bizarres des rêves. Les résultats des quatre études suggèrent que le sommeil aux ondes lentes et le sommeil paradoxal sont différemment impliqués dans le traitement de la mémoire épisodique. Le sommeil aux ondes lentes pourrait être implique dans la consolidation de la mémoire épisodique, et le sommeil paradoxal, par l'entremise du rêve, pourrais avoir le rôle d'introduire de la flexibilité dans ce système mnémonique. / The present dissertation examines relationships between sleep, episodic memory and dreaming. In Articles I and II we use a novel virtual reality (VR) task in conjunction with a rapid eye movement (REM) sleep deprivation (REMD) paradigm and dream sampling to examine the hypothesis that REM sleep and dreaming are involved in the consolidation of episodic memory. REM sleep was associated with the successful recall of the spatial aspects of emotionally charged elements of the VR task. Similarly, dreaming was associated with improved performance on the spatial aspects of the recall task. Recall of the factual and perceptual aspects of episodic memories formed with the VR task was associated with increased slow wave sleep (SWS) during the post-exposure night. Overall, the results suggest that SWS is associated with the perceptual and factual aspects of episodic memories while REM sleep is not, a finding which may relate to observations that REM sleep dreaming is composed of deconstructed fragments of loosely associated episodic memories. Study II examines the hypothesis that a function of dreaming may be to create new associations between previously unrelated memory items. A participant, highly trained in introspection and mentation reporting, was awakened 43 times during theta bursts at sleep onset and provided detailed reports of resulting imagery and associated memory sources. This technique provided evidence that elements of distally related memory sources are brought together in temporal and spatial proximity within a novel context provided by the dream, suggesting a role for dreaming in memory processing. To allow for this possibility, we speculate that dreaming experiences may be functionally equivalent to waking experiences in their ability to induce neural plasticity. Study III addresses an aspect of this functional equivalence by examining if dream bizarreness is incompatible with behavioral and cognitive features associated with waking state experience-driven plasticity, i.e., whether the dreamer can act upon, emote and be motivated towards an element of the dream that is bizarre and that violates basic assumptions of physical reality. The results demonstrate a dissociation in cognitive ability during dreaming characterized by a selective deficiency in appreciating bizarreness in face of a maintained ability for logical thought. This finding thus addresses the problem of the wake-like mind reflecting upon dream bizarreness and suggests that dreaming is a state in which the cognitive aspects associated with synaptic plasticity (attention, emotion and motivation associated with believing a situation to be reality) are present while allowing for the presentation of memory item combinations which may transcend the limits of physical reality. The results of the four studies are discussed in light of how REM and SWS sleep stages are differentially involved in specific aspects of episodic memory (episodic replay vs. episodic novelty) and the possible role that dreaming, as a driver of synaptic plasticity, may have in these relationships.

Cognitive functioning is important for managing work and life in general. However, subjective cognitive complaints (SCC), involving self-perceived difficulties with concentration, memory, decision making, and clear thinking are common in the general and in the working population and can be coupled with both lowered well-being and work ability. The present thesis investigated the extent to which SCC among people in the work force can be explained by objective cognitive functioning (study I &amp; II) and working conditions (study III), utilizing samples from the working population. The potential roles of other common psychological problems which often co-occur with SCC were also investigated in studies I-III. In Study I, high levels of SCC were associated with significantly poorer episodic memory performance during high executive demands and a trend was found towards poorer episodic memory, while not being associated with semantic memory. In Study II, high levels of SCC were associated with significantly poorer executive cognitive performance on all three executive cognitive tests used. Symptoms of depression, chronic stress and sleeping problems were found to play an important role in the relations between SCC and episodic memory during divided attention in study I and executive cognitive functioning in study II. In Study III, in all cross-sectional data analyses, high quantitative demands, information and communication technology (ICT) demands, underqualification in the work situation and inter-personal conflicts were positively associated with SCC, whereas social support, good resources at work and overqualification in the work situation were negatively associated with SCC. In all prospective data analyses, quantitative job demands, ICT demands and underqualification were positively associated with future SCC, including when adjusted for baseline cognitive complaints. The findings may guide prevention of and interventions for SCC among people in the work force. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 2: Accepted.</p>

La domanda "Che cos’è lo spazio?" è sempre stata un tema centrale per la filosofia, ed è diventata di interesse anche per la psicologia cognitiva e per le neuroscienze, con una domanda cruciale strettamente legata: "Dove sono io?". Lo sforzo per collegare le risposte a queste due domande mira proprio a comprendere la complessa relazione che esiste tra lo spazio interno ed esterno, che è l'obiettivo finale di questo lavoro. L'idea è che la nostra posizione nel mondo influenzi fortemente il modo in cui codifichiamo, archiviamo e recuperiamo dalla memoria un layout spaziale. Inoltre, questo layout spaziale serve da impalcatura che vincola tutte le informazioni relative al nostro passato, presente e futuro, e tutte le esperienze legate al nostro corpo. All’interno di un approccio enattivo, si suggerisce una sincronizzazione continua (cioè, il “mental frame syncing") tra una rappresentazione allocentrica indipendente dal punto di vista allocentrica (i.e. che include solo relazioni oggetto-oggetto astratte) e una rappresentazione allocentrica dipendente dal punto di vista (i.e. che include informazioni sulla nostra direzione egocentrica attuale) possa permettere di posizionare il corpo nello “spazio memorizzato” rendendo più semplice la traduzione di questo in un “lived space” di cui si necessita per navigare, per ricordare il passato e per sentire il corpo. Sulla base di queste premesse teoriche, quattro studi sperimentali saranno presentati per studiare il ruolo del mental frame syncing come un principio di allineamento centrato sull’osservatore nei processi di codifica e di recupero delle informazioni. / The question "What is space?" has always been a central topic for philosophy, and a closely linked crucial question becomes of interest for cognitive psychology and neuroscience, that is "Where am I?" The efforts to answer these two questions are means to better understanding of the complex relation between the outer and the inner space, which is the final goal of this work. The idea is that that our bodily position in the world strongly affects the way in which we encode, store and retrieve a spatial layout. Moreover, this spatial layout serves as a scaffold, binding all the information of our past, present, future and body-related experiences. Within an enactive approach, it is suggested that this continuous synchronization (namely, the “mental frame syncing”) of an allocentric viewpoint-independent representation (i.e. including only abstract object-to-object relations) and an allocentric viewpoint-dependent representation (i.e. comprising information about our current heading) may permit to place current bodily position in the “memorized space" making easy the translation of it into a “lived space” that it is needed to navigate, remember the past and feel the body. On these theoretical premises, four experimental studies will be presented to investigate the role of mental frame syncing as an alignment principle centred on observer the processes of encoding and retrieval of information

La mémoire épisodique donne la capacité de voyager mentalement dans son propre passé. En cela,elle permet de faire fi du temps qui passe pour pouvoir revivre des événements passés. Ce travail dethèse évalue l’hypothèse selon laquelle la mémoire épisodique et la sensation de revivre un événementpassé (i.e., conscience autonoëtique) sont basées sur une fluence dans la reconstruction de l’épisode,reconstruction impliquant une mise à jour égocentrée. Cette proposition est développée dans le modèlede Gomez et collaborateurs (Gomez, Rousset & Baciu, 2009) qui propose que la mise à jourégocentrée permette de ré-instancier un point de vue spatialisé égocentré sur l’évènement remémoré.Ce travail de thèse a amené de nouveaux arguments en faveur de ce modèle, en évaluant à la foisl’approche attributionnelle de la mémoire épisodique et le lien fonctionnel entre la mise à jourégocentrée en ligne et la mémoire épisodique. Une première série d’études met en évidence uneinfluence de la fluence du processus de mise à jour égocentrée sur la conscience autonoëtique.L’augmentation artificielle de la fluence de mise à jour égocentrée, lors de la reconnaissance,augmente le sentiment de conscience autonoëtique et ce uniquement lorsque la reconnaissanceimplique une reconstruction. Une seconde série d’études permet de mettre en évidence un effetd’interférence du processus de mise à jour égocentrée en ligne sur la récupération épisodique.Actualiser sa position dans l’espace lors d’un déplacement a beau être un processus automatique, celaralentit spécifiquement le rappel de source. Enfin, une étude impliquant des patients atteints de lamaladie d’Alzheimer, met en évidence une dissociation entre les compétences en mise à jourégocentrée chez ces patients. Ces résultats sont discutés dans le cadre du modèle de Gomez etcollaborateurs et en regard d’une conception incarnée et située de la cognition. / Episodic memory makes it possible to mentally travel back in our own past; it breaks the law of theunidirectionality of time, and allows us to mentally relive past events. The main goal of this work wasto investigate whether episodic memory and the subjective feeling of reliving a past event (i.e.,autonoetic consciousness) arise from the fluency of the reconstruction process of the event. Thisreconstruction would involve the process of egocentric spatial updating with self-motion. Thishypothesis was first developed in Gomez and colleagues' model (Gomez, Rousset, & Baciu, 2009) thatsuggests that egocentric updating re-instances an egocentric spatial point of view on the rememberedevent. The present work brings additional behavioral evidences to this model by assessing both theconception of attributional episodic memory and the functional link between online egocentricupdating with self-motion and episodic memory. A first set of studies showed that enhancingartificially the fluency of the egocentric updating process, during the recognition phase, increasedautonoetic consciousness. Moreover, such phenomenon only happened when recognition involved areconstruction process. A second set of studies showed that performing an online egocentric updatingwith self-motion interfered with remembering. Although the updating of its own position though selfmotionis automatic, it specifically slows down source recall. Finally, a last study showed adissociation between preservations of and deficits of egocentric spatial updating abilities in patientssuffering from Alzheimer's disease. The results of these studies are discussed in the context of Gomezand colleagues' model, and in terms of embodied and situated cognition.

Aging, also in the absence of pathological conditions, is associated with cognitivedecline, especially in so called fluid abilities, such as episodic memory andexecutive functions. Due to an ongoing demographic shift, a larger part of thepopulation will reach higher ages, and more people will be affected by age-relatedcognitive decline. Finding ways of counteracting this development have the potentialof having large benefits for both individuals and society. It has long beenknown that living in environments that are rich in terms of cognitive challengescan affect cognitive ability in old age. In this regard, intervention studies in whichthe amount of cognitive stimulation is manipulated can therefore generate insightsto the causality of such effects in specific cognitive functions. Cognitive trainingas means to counteract negative effects of aging on cognition has received a lot ofscientific interest in the last decades.This focus of this thesis is cognitive training interventions, which is studiedfrom several perspectives. In Study i, the aim was to investigate the extent towhich executive functions can be strengthened by training in younger and olderadults, and to which degree such training generalize to other measures of cognition.Although a large body of research has been investigating training of workingmemory and executive functions in recent years, the results are diverse, and fewhave been targeting executive functions broadly with training programs based ontheoretical models of executive functions. Study i showed that despite a broadtraining program targeting three executive functions (updating, shifting and inhibition),it did not lead to transfer beyond the very near in old adults. The youngerhowever showed transfer effects to measures of working memory.In Study ii, the focus was on studying how the effects survive across time.There is limited knowledge about long-term effects of process-based training andthe results showed that the training effect was stable after 1.5 years, while only thenearest transfer effect was still significant in both younger and older adults.Study iii focused on individual factors affecting gain and maintenance thereofin a sample of older individuals. We used a strategy-based intervention focusingon episodic memory performance with a number-consonant mnemonic which is amnemonic for memorizing digit-codes. A different set of predictors was observedfor baseline episodic memory performance and training gain. Those that are betteroff in terms of episodic memory performance, also gain more in the episodic memorycriterion task. Further, a higher rate of processing speed was also important.Lastly, better verbal knowledge also influence gain beyond the other factors. Theresults have both theoretical implications regarding how plastic cognitive functionsare, and practical, in terms of how to best design training programs. / Över hela världen blir vi äldre. År 2050 kommer en femtedel av jordens befolkningvara 60 år eller äldre, att jämföra med en knapp tiondel år 1950. Det är förstås enpositiv utveckling men en åldrande befolkning innebär också att vi står inför flerautmaningar. En sådan rör det kognitiva åldrandet. Vi vet att åldrande kan leda tillnedgång i vissa kognitiva förmågor, såsom det episodiska minnet samt exekutivafunktioner. Episodiskt minne är vår förmåga att komma ihåg upplevda händelserknutna till tid och rum. Exekutiva funktioner är ett begrepp som inbegriper vårförmåga att hålla en plan aktiv medan vi utför den, utan att distraheras av tankareller externa störningsmoment. Genom att studera effekter av träning hos yngreoch äldre vuxna på sådana kognitiva funktioner kan vi få kunskap om till vilkengrad de kan förbättras och om denna förbättringspotential är olika beroende påålder. Vi vet sedan tidigare att människor som under sin livstid lever ett kognitivtstimulerande liv också till viss del är skyddade mot nedgång i kognition underåldrandet. Träningsstudier kan ge kunskap om kausaliteten i sådana fynd.Studie i i denna avhandling behandlar träning av exekutiva funktioner föryngre och äldre vuxna. Träningsprogrammet konstruerades utefter en teoretiskmodell som beskriver exekutiva funktioner som bestående av förmågan att inhiberastörande stimuli eller överlärda responser, förmågan att uppdatera informationi arbetsminnet, och förmågan att skifta mellan att utföra olika uppgifter. Resultatenvisade att de yngre kunde generalisera träningseffekten också till otränadearbetsminnesuppgifter, medan de äldre endast visade förbättring på otränade uppgiftersom hade stora likheter med de tränade.I Studie ii undersöktes hur mycket av träningseffekterna som kvarstod ettoch ett halvt år efter träningen. Resultaten visade att både för yngre och äldreså kvarstod effekten på tränade uppgifter samt en av uppgifterna som hade stortöverlapp med träningsuppgifterna, för både unga och äldre.I Studie iii studerades ett strategibaserat träningsprogram för episodisktminne. Fokus låg på att undersöka vilka individuella kognitiva faktorer sompåverkar förbättring som följd av träning. Resultaten visade att de med högre förmågai kognitiv bearbetningshastighet samt verbal förmåga var de som hade bästförutsättningar för förbättring.Resultaten från dessa studier är av både teoretisk relevans i och med att deökar förståelsen för träningsbarheten av exekutiva funktioner, samt har praktiskrelevans för utformning av träningsprogram.

Il a été suggéré que lorsqu’une trace de mémoire consolidée est rappelée (réactivée), elle devient instable et sujette aux modifications avant de se stabiliser à nouveau en mémoire à long terme. Nous avons récemment démontré que lorsque la réactivation d’un souvenir négatif est couplée à l’exposition à un stress psychosocial, le souvenir de l’évènement négatif est augmenté de façon durable. En se basant sur ces résultats, le but de cette thèse est de préciser le rôle du stress psychologique et physiologique (hormones de stress) sur la modulation de souvenirs réactivés. Plus précisément, la première étude visait à déterminer si le cortisol, hormone de stress majeure, est un joueur clé dans la modulation des souvenirs réactivés. Pour ce faire, nous avons inhibé pharmacologiquement les niveaux de cortisol au moment de la réactivation d’un souvenir contenant des segments neutres et négatifs. Les résultats démontrent que la réactivation du matériel négatif est amoindrie lorsque les niveaux de cortisol sont inhibés, et cet effet est toujours présent quatre jours plus tard. Étant donné que les stimuli utilisés jusqu’à maintenant ont une faible validité écologique, nous avons voulu déterminer si d’autres types de mémoires pouvaient également être modulables lors de leur réactivation. L’objectif de la deuxième étude était donc de déterminer si les mémoires autobiographiques collectives sont modulables par le stress au moment de leur réactivation. Pour ce faire, nous avons exposé les participants à de vrais extraits de journaux, neutres ou négatifs, afin de réactiver les mémoires collectives associées à ces évènements. Par la suite, tous les participants ont été exposés à un stress psychosocial et leur mémoire des extraits a été évaluée la journée suivante. Les résultats démontrent que les femmes ayant lu les nouvelles négatives avaient une réactivité physiologique accrue face au stresseur et une mémoire augmentée de ces mêmes nouvelles le jour suivant. Ce phénomène n’était cependant pas observable chez les hommes. Le but de la troisième étude était de déterminer si les mémoires autobiographiques personnelles sont modulables par le stress au moment de leur réactivation. Nous avons demandé aux participants de se remémorer deux évènements de leur passé, négatifs ou neutres. Par la suite, ils ont été exposés à un stress psychosocial et leur mémoire pour ces mêmes évènements a été évaluée à nouveau la journée suivante. Les résultats démontrent que les mémoires autobiographiques personnelles réactivées ne semblent pas être modulables par l’exposition à un stresseur. Globalement, les résultats de cette thèse démontrent que le cortisol a la capacité de moduler des souvenirs négatifs réactivés, mais que la nature (extrinsèque vs. intrinsèque) et l'intensité des souvenirs réactivés sont des facteurs déterminants pour que ce phénomène prenne place. / It has been suggested that when a consolidated memory trace is recalled (reactivated), it becomes active and sensitive to modifications before stabilizing again in the long-term memory system. We have recently demonstrated that when the reactivation of a negative memory is followed by exposition to a psychosocial stressor, the memory for the negative material is enhanced in a long-lasting manner. Based on these results, the goal of this thesis is to clarify the role of physiological (stress hormones) and psychological stress on the modulation of reactivated memories. More precisely, the first study aimed to determine whether cortisol, a major stress hormone, is a key player in the modulation of reactivated memories. To do so, we have pharmacologically inhibited cortisol levels at the time of reactivating a memory composed of neutral and negative segments. Results showed that the reactivation of the negative material is decreased when cortisol levels are inhibited and this effect is still present four days later. Given that the stimuli used so far have a weak ecological validity, we wanted to determine whether other types of memories could also be modified upon their reactivation. The goal of the second study was to examine whether collective autobiographical memories were sensitive to the effects of stress at the time of reactivation. To do so, we have exposed participants to real newspaper excerpts, either neutral or negative, in order to reactivate the collective memories associated to these events. We have then exposed all the participants to a psychosocial stressor and their memory for the excerpts was assessed the following day. Results showed that women who have read negative news excerpts had a more pronounced physiological reactivity to the stressor and an increased memory for these news the following day. This phenomenon, however, was not observed in men. The goal of the third study was to determine whether personal autobiographical memories were sensitive to the effects of stress at the time of their reactivation. We have asked participants to recall two personal events, either negative or neutral. We then exposed them to a stressor and their memory for these events was tested the following day. The results showed that reactivated personal autobiographical memories were not sensitive to stress. Globally, the results of this thesis show that cortisol has the capacity to modulate reactivated negative memories, but that the nature (extrinsic vs. intrinsic) and the intensity of the memories are determining factors for this phenomenon to occur.

Adults can mentally relive experiences from their past and anticipate possible future events, a process called mental time travel (MTT). Recently, several theorists have argued that the ability to mentally travel through time may not emerge until 3- to 5-years of age. This proposal is based on evidence from a wide range of research, including investigations into children’s recall, planning and differentiation of the times of events in the past and the future. However, as yet there has been no dedicated effort to find out how and when MTT develops. The current series of studies brought together a wide range of resources with the aim of designing a series of novel paradigms to measure aspects of MTT development between 3- and 5-years of age. The first of these novel approaches asked children to report events that occurred to them “yesterday” and would occur to them “tomorrow”, revealing that by 4- to 5-years of age most children could accurately do so. Another series of studies examined children’s ability to anticipate a different, future situation, finding that only by 4- to 5-years did children’s behaviour reflect differences in an anticipated future environment. Subsequent studies focusing on children’s discrimination of past and future also suggested that by 4- to 5-years children could distinguish the different causal impact of past and future events on the present. Another task revealed that during the preschool years children become better at differentiating the times of events from throughout their own lifespan. These new data provide support for the claim that the ability to mentally travel into one’s own past and future emerges during the preschool years. This thesis describes the first directed investigation into the development of MTT as a whole, bringing together much of the empirical and theoretical literature for the first time. The tasks designed are new approaches to investigating MTT and represent a starting point for future research. This thesis also introduces and discusses theories for the development of MTT, aiming to stimulate discussion not just of when it emerges, but how, and what processes may underlie the transition.

Adults can mentally relive experiences from their past and anticipate possible future events, a process called mental time travel (MTT). Recently, several theorists have argued that the ability to mentally travel through time may not emerge until 3- to 5-years of age. This proposal is based on evidence from a wide range of research, including investigations into children’s recall, planning and differentiation of the times of events in the past and the future. However, as yet there has been no dedicated effort to find out how and when MTT develops. The current series of studies brought together a wide range of resources with the aim of designing a series of novel paradigms to measure aspects of MTT development between 3- and 5-years of age. The first of these novel approaches asked children to report events that occurred to them “yesterday” and would occur to them “tomorrow”, revealing that by 4- to 5-years of age most children could accurately do so. Another series of studies examined children’s ability to anticipate a different, future situation, finding that only by 4- to 5-years did children’s behaviour reflect differences in an anticipated future environment. Subsequent studies focusing on children’s discrimination of past and future also suggested that by 4- to 5-years children could distinguish the different causal impact of past and future events on the present. Another task revealed that during the preschool years children become better at differentiating the times of events from throughout their own lifespan. These new data provide support for the claim that the ability to mentally travel into one’s own past and future emerges during the preschool years. This thesis describes the first directed investigation into the development of MTT as a whole, bringing together much of the empirical and theoretical literature for the first time. The tasks designed are new approaches to investigating MTT and represent a starting point for future research. This thesis also introduces and discusses theories for the development of MTT, aiming to stimulate discussion not just of when it emerges, but how, and what processes may underlie the transition.