Donald Rumsfeld reminded us that “as we know, there are known knowns; there are things that we know that we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns, the ones we don’t know we don’t know.” History has not yet resolved how accurately he could distinguish between these mental states. If people of his level of influence become less able to distinguish between them as they grow older this becomes an inconvenience for them and harsh risk for the rest of us.
I forget things more things more often than I did when I was young. Folk wisdom and a vast literature tell me that I should not be surprised. Forgetting is irritating but Mind-Google crashes can be bypassed by searching the Web. If this also fails I can comfort myself that the information is so abstruse that I can be excused for losing it and I can still visit the friendly paper-libraries in which I have been happy all my life.
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I often write lists of things to do and sometimes remember to use them. Most of my memory lapses are apparent only to me but brain betrayals sometimes becomes publicly embarrassing when I stammer for a word that I am convinced that I know but that sniggers at me for hours from the dark of my mind. This is especially awkward when it is the name of somebody I have known for years who has just cheerfully greeted me. Being confident that a lost word will appear later, usually when it is no longer needed, is an example of “knowing that we know” something while being unable to recall it. These are called “tip of the tongue” experiences or, by psychologists who seem to feel that acronyms are cool and business-like, TOTs. TOTs are common at any age but do happen more often as we grow old. My most memorable recent disastrous TOT event happened during a speech I had to give at my partner’ birthday party when, for two excruciating minutes, I could not find the first name of an excellent brother in law whom I havv valued for 40 years. We know that we know these mislaid words because we can recall quite a lot about them: usually their initial letters, their approximate lengths and numbers of syllables and also, sometimes, rhymes for them, and we search only for the sound of a word for which we already have a correct definition1.
What of “known unknowns”? How can I be sure that I don’t know something? Or that one of my cupboard drawers does not hide a purple sock? Does age also make us less accurate at knowing what we don’t know until our heads fill with things that we no longer know that we know, just as our cupboards get crammed with stuff we have forgotten about? How accurately can we confirm oblivion ?
My fellow psychologists are all extraordinarily clever, kind, gentle and decent folk but they do tend to evade the questions I would most like them to answer and will persist in trying others instead. I have learned to live happily among them for nearly 60 years but still find them slightly earnest and humourless. This is illustrated by the acronym they use to give academic dignity to attempts to quantify our uncertainty about our memories: “FOKs”, or “Feelings of Knowing” – which are people’s ratings of how confident they are that they know something that they cannot immediately recall, or how sure they are that that they never will remember it. Results from comparisons of FOK ratings between older and younger people vary. At least two studies suggest that accuracy and confidence of FOK judgements do not greatly change with age2,3 but do change with the topic probed. For instance older people are most confident of their ignorance in an area, computer studies, about which they know little3. For me this seems entirely believable, like being correctly convinced that I cannot remember anything about Patagonia because I am sure that I have never been there. I find it hard to feel surprised. Other studies have also found that age does not affect FOK ratings for rare words e.g.4.
A different question is whether there are some, particular, parts of the brain that are involved in judgments about what we know and do not know, and whether these are different from the areas that are involved in effective storage, and in immediate and successful retrieval of information. Another study found that FOK judgements do become less reliable with age and that age-related losses in FOK accuracy were predicted by scores on behavioural measures used to diagnose frontal lobe damage. This last result would square well with any evidence that FOK accuracy declines with age because age-related changes occur earlier and proceed faster in our frontal lobes than in other parts of our brains. The idea of a connection between FOKs and the frontal lobes was strengthened by an experiment in which young patients who suffered “a broad spectrum of damage to the frontal cortex” were given sentences to remember. Then they were tested by being given each sentence without the last word, which they then had to produce, or to rate how strongly they felt that they would, or would not recognise it if it was shown to them. Volunteers were less accurate if they were asked to make FOK judgements and to rate their confidence in them before the sentences were re-read but did much better if they made these judgements after they had actually tried to recall the words6. Again I find it hard to be surprised that I may be better at judging whether or not I know something after I have had a diligent try at remembering it. A more interesting point is that these results show that FOK accuracy does not depend on calendar age but on the extent to which ageing has affected the frontal lobes of the brain; – areas that are known to manage planning and organisation of information in memory.
Other neuropsychological studies have used brain imaging (fMRI) to study changes in activation in volunteers’ frontal lobes while they rate their confidence in their FOK judgements. One experiment found that, during FOK ratings, the left dorsolateral, left anterior, bilateral inferior, and medial prefrontal cortex becomes significantly more active than other brain areas7. Activation of these areas also becomes greater as peoples’ feelings that they know a mislaid word or fact become stronger. These frontal “FOK areas” were activated during uncertain, but not during successful recall.
Another of many studies8 also provides evidence that the particular parts of the brain that are responsible for monitoring the accuracy and reliability of recall are anatomically distinct from those that are essential to storage and immediately retrieve information. Volunteers tried to answer general knowledge questions and their brain activity, measured by fMRI scanning, was compared during TOT states, (defined as recall failures accompanied by a strong feeling of imminent retrieval), FOK states, (defined as recall failures accompanied by a feeling of that the item would be recognised if seen again) ) and confident ”Don’t Know” responses. During TOTs there was increased activation in the anterior cingulate, right dorsal and inferior, and bilateral anterior, prefrontal cortex. During both TOT and FOK states there were also comparable increases in levels of activation in parietal regions. Activation during TOTs and FOKs was greater than during confident “Know” and “Don’t know” responses. It seems that if we are sure that we know something we can say so immediately and confidently. If we are not sure, we then puzzle about it, working through all possible scenarios and associations that might evoke the information we seek.This active and systematic scanning for possible associations involves activity in frontal and parietal areas of the brain that are not, or are much less strongly, involved during confident immediate recall.
So the parts of the brain that monitor whether or not our memories are reliable are different from those that are more directly involved in storing and successfully retrieving information from memory. Nevertheless, in my view, this is not yet logically convincing evidence that memory monitoring and storing and retrieving information are separate and independent processes. If recall is not immediate we may call on additional brain areas to work out whether or not it may eventually be possible.
What happens when the general efficiency of our memories declines – as it does as we grow older? A neat study9 compared FOK judgements among 20 elderly patients diagnosed with “Mild Cognitive Impairment” (MCI), which is usually, but not invariably, a sign of impending dementia. As expected, the MCI group remembered less than their age-matched controls. They also made more inaccurate and unrealistically optimistic predictions that they would later recognise information that they were given. The more their other cognitive abilities,such as intelligence, had declined the greater was their false optimism that they would eventually remember.
It seems that as I experience increasing cognitive impairment I will become more convinced that I do know things that, in fact, I can no longer remember. Not a cheerful thought for me, or for those who will have to cope with me. Which is why I try to get what comfort I can from another study in which patients diagnosed with dementias knew what they would, and would not later recognise10.
As I trundle further into Struldbruggery shall I be cheerfully oblivious of my growing ignorance or gloomily aware of remorseless evaporation of knowledge? Will I know that I have lost something but not know what this is, or shall I be unaware that anything has changed? No doubt we shall see.
1. James, L. E., & Burke, D. M. (2000). Phonological priming effects on word retrieval and tip-of-the-tongue experiences in young and older adults. Journal of Experimental Psychology: Learning, Memory, and Cognition, 26, 1378.
2.Marquié, J. C., & Huet, N. (2000). Age differences in feeling-of-knowing and confidence judgments as a function of knowledge domain. Psychology and aging, 15(3), 45
3. Eakin, D. K., & Hertzog, C. (2012). Age invariance in feeling of knowing during implicit interference effects. The Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 67(5), 555-562.
4. Allen-Burge, R., & Storandt, M. (2000). Age equivalence in feeling-of-knowing experiences. The Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 55(4), P214-P223.
5. Souchay, C., Isingrini, M., & Espagnet, L. (2000). Aging, episodic memory feeling-of-knowing, and frontal functioning. Neuropsychology, 14(2), 299.
6. Schnyer, D. M., Verfaellie, M., Alexander, M. P., LaFleche, G., Nicholls, L., & Kaszniak, A. W. (2004). A role for right medial prefrontal cortex in accurate feeling-of-knowing judgments: evidence from patients with lesions to frontal cortex. Neuropsychologia, 42(7), 957-966.
7. Kikyo, H., Ohki, K., & Miyashita, Y. (2002). Neural correlates for feeling-of-knowing: an fMRI parametric analysis. Neuron, 36(1), 177-186.
8. Maril, A., Simons, J. S., Weaver, J. J., & Schacter, D. L. (2005). Graded recall success: An event-related fMRI comparison of tip of the tongue and feeling of knowing. NeuroImage, 24(4), 1130-1138.
9. Perrotin, A., Belleville, S., & Isingrini, M. (2007). Metamemory monitoring in mild cognitive impairment: Evidence of a less accurate episodic feeling-of-knowing. Neuropsychologia, 45(12), 2811-2826.
10. Moulin, C. J., James, N., Perfect, T. J., & Jones, R. W. (2003). Knowing what you cannot recognise: Further evidence for intact metacognition in Alzheimer’s disease. Aging, Neuropsychology, and Cognition, 10(1), 74-82.