Tuesday, 24 February 2015

Remembering, Imagining, False Memories, and Personal Memories

This is the fourth in our series of posts on the papers published in a special issue of Consciousness and Cognition on the Costs and Benefits of Imperfect Cognitions. Here Catherine Loveday summarises her paper, co-written with Martin Conway, 'Remembering, Imagining, False Memories and Personal Memories'. 

Ogwo David Emenike once wrote, 'Our imagination goes ahead of us, bringing our yesterday's imaginings into present realities'. This beautifully encapsulates the extraordinary capacity and need that humans have for mental time travel but, more than that, it illustrates the inextricable relationship between memory and imagination. When we remember we imagine and when we imagine we use our memory. Both are mental constructions based on past experience and there is significant evidence to suggest that the same brain structures are involved when we remember and when we imagine.

The building blocks for both remembering and imagining are semantic memory – the knowledge we have of our world – and episodic memory – sights, sounds, smells, thoughts, and feelings that we have experienced. These are used to create a conscious experience that takes us out of the present moment and into another place that may be anywhere in the future or the past. So for example, I can easily call to mind the last time that I met a particular friend but by using much of the same knowledge and experience I can also imagine what a future encounter with the same friend might be like.

We call this the remembering-imagining system and in our paper we discuss some of the features of this system. One important characteristic of remembered and imagined experiences is that they are driven by cues. So we may actively remember something by using a series of internally generated cues, for example, thinking about the place I met my friend or which day of the week it was. But equally, memories can be triggered when we encounter random external cues, for example overhearing my friend’s name or smelling her perfume. In all cases, there is a temporary but stable pattern of brain activity that gives rise to a feeling of remembering and by and large we are in control of this process.

A particularly interesting feature of the remembering-imagining system is that the further away we travel in time from the present moment, the less specific and accessible the memories and images become. So while we might be able to picture in quite vivid detail what we may be doing in an hour’s time, the images of what we might be doing in a week’s time will be more generic and less detailed and still more so for something we may be doing in five years time. Similar is true when we travel back in time.

So to what extent can we trust our memories if they are mentally constructed using the same processes we use to imagine? We argue that memories can be viewed along two dimensions: the extent to which the remembered experience reflects the details of what actually happened – we call this correspondence – and the extent to which this memory is in line with other memories we hold and with the beliefs and feelings we have about our self – we call this coherence. We argue that although some memories may be higher in correspondence than others, this is not always central to our ability to function in the world. Rather, it may be that the coherence of our memories and imaginings is what gives us a sense of continuity and, most importantly, supports our sense of self. 


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