Daniel Munro is a PhD student at the university of Toronto. He's especially interested in the nature and epistemic value of sensory imagining that represents the actual world, as well as the relation of such imagining to perception and memory.
A post by Daniel Munro
During testimonial knowledge transmission between subjects, a testifier who knows something verbally conveys it to a listener, who comes to know that same thing by trusting what the testifier has said. Things go epistemically awry when a listener trusts a testifier who intentionally or unintentionally says something false, in which case the listener forms a testimonial belief that doesn’t amount to knowledge.
One question we can ask about the epistemology of testimony concerns the basis of testimonial knowledge: when knowledge is transmitted from testifier to listener, what is the evidential or justifying basis of the knowledge the listener acquires?
According to one intuitively plausible view, a listener can have the same degree of justification in a case of genuine testimonial knowledge as in a case where she mistakenly trusts an unreliable testifier. On this view, testimonial evidence consists of facts about what a testifier has asserted or presented as true, perhaps along with facts about how reliable the testifier appears to be. Since an unreliable testifier can assert something while coming across as reliable, a listener could have an equally justified belief in a case of unreliable testimony as in a case of knowledgeable testimony (see, e.g., Brown 2018, ch. 2 for this sort of view).
The kind of view just described is perhaps the standard among epistemologists of testimony. But another possible view is that, when a testifier transmits her knowledge that P to a listener, the basis of the listener’s knowledge includes the testifier’s knowledge that P.[i] This view implies that the listener’s justificatory basis must be different when a testifier is knowledgeable versus unreliable. There’s again something intuitive about this view: we typically trust testifiers when we take them to be knowledgeable, so it doesn’t seem like a huge stretch to say a listener’s testimonial knowledge that P can be based in part on her interlocutor’s knowing that P.
What does all this have to do with the imagination? My proposal in this post is that certain empirical facts about mental imagery’s role in testimonial knowledge transmission help motivate the second kind of view of testimonial justification—that a testifier’s knowledge constitutes part of the basis of a listener’s testimonial knowledge.
The scope of this proposal will be restricted to certain kinds of testimony: cases in which a testifier describes some concrete scene or event. This could be, for example, describing a past event one experienced first-hand or heard about second-hand, describing an event one expects to occur in the future, or describing some particular part of the world, like the layout of a restaurant or the façade of a building.[ii] Research on the psychology of speech production and comprehension reveals that, in cases of this sort, mental imagery plays a prominent role in the minds of both testifiers and listeners.
First, take the testifier side. Neuroimaging evidence suggests that producing descriptions of a scene involves visualization and other mental imagery-construction processes (Mar 2004; Zadbood et al. 2017). Such speech production seems to involve episodically remembering or sensorily imagining a scene and then “reading off” descriptions from the mental image before one’s mind. This makes intuitive sense. You might try yourself walking through the process of describing some past event you witnessed. When you do, it seems inevitable that you’ll proceed by episodically remembering that event and basing your descriptions on this memory. Such mental imagery, then, is the means by which a testifier brings to mind the knowledge she wants to share with a listener.
On the listener side, there’s good reason to think that, in the kind of case I’m concerned with, acquiring knowledge from testimony also involves constructing mental imagery. It’s widely recognized among psycholinguists that comprehending and keeping track of an interlocutor’s descriptions of a scene involves mentally constructing a “situation model” of the scene being described, where such models are again imagistic in format (Zwaan 2016). Moreover, such situation models are the representations we commit to long-term memory when it comes to retaining information gleaned from testimony (Zwaan and Radvansky 1998; Zacks, Mar, and Calarco 2018; McClelland et al. 2019). In other words, rather than remembering a testifier’s specific words or utterances, we instead store a representation of the situation they described to us. (In fact, we often forget a testifier’s particular words or even who the testifier was, while retaining a representation of the situation they described.) This suggests that such representations are themselves the format of our testimonial knowledge: imagistic situation modelling is the very process by which we acquire information about the world from testimony and store that information for possible retrieval later on.
So, imagery is involved on both ends of testimonial knowledge transmission: it’s how the testifier brings to mind knowledge to share and it’s how the listener acquires testimonial knowledge.
Moreover, it’s also the case that the neural patterns underlying situation modelling in the mind of the listener typically mirror the neural patterns underlying speech production in the mind of the testifier (Hasson et al. 2012; Silbert et al. 2014). In fact, this kind of “neural coupling” between the brains of two subjects seems to be required for successful testimonial knowledge transmission to even occur: the degree to which a listener comprehends and can later recall the details of testimony correlates with the degree of similarity between neural processes in the listener and speaker (Stephens, Silbert, and Hasson 2010; Zadbood et al. 2017). One plausible construal of all this is that, in testimonial knowledge-transmission, the function of the testifier’s speech is really to cause the listener to construct a representation that mirrors the one in the testifier’s mind—i.e., testimony causes the mental imagery of the world in the testifier’s mind to be re-capitulated in the mind of the listener (cf. Hasson et al. 2012).[iii]
I think these facts about mental imagery in the minds of listeners and testifiers have implications for how we conceptualize the basis of testimonial knowledge. They show that, when knowledge is transmitted between subjects, the basis of the listener’s knowledge includes the representation in the mind of the testifier—i.e., it includes the imagining or episodic memory on which the testifier based her testimony. It’s not merely that the testifier puts some information “out into the world” in the form of an assertion and the listener hears this assertion and picks up that information from it. Rather, there’s a more intimate relationship between the mind of the testifier and listener: the listener is prompted, by the testifier’s utterances, to construct a representation of a scene which resembles the testifier’s representation. This makes it seem intuitive to say that the listener’s representation is in part based on the testifier’s representation.
To make this seem even more intuitive, consider the fact that, if a listener realizes her imagining failed to sufficiently resemble the testifier’s imagery, she’ll think something has gone wrong. Suppose I’m imagining some event you’re describing and that I imagine you witnessing it firsthand. Eventually, though, I realize you’ve been describing something you merely imagined but didn’t observe directly. I’m likely to say something like, “Wait, I was imagining that you were actually there,” then try to revise my imagining to bring it more in line with yours. Here, it seemed to me I was imagining based on your representation of the event (since I thought your representation was a memory), but my imagining failed to match yours in an important respect.
Everything I’ve just argued has implications for how we answer the question about testimonial justification with which I began: whether the basis of a listener’s testimonial knowledge includes the testifier’s knowledge or merely facts about what the testifier asserted and her apparent reliability. I’ve argued that listeners acquire testimonial knowledge by imagining the scene a testifier is describing, in a way that’s based on the imagery of that scene in the testifier’s mind; I’ve also argued that the testifier’s mental imagery is the means by which she brings to mind her knowledge of the scene she’s describing. So, the listener’s testimonial knowledge is indeed based on the testifier’s knowledge. There’s thus more to the basis of testimonial knowledge than merely what the testifier asserts and how she outwardly seems to the listener.
What about cases of false testimonial belief rather than knowledge? Such cases can arise when a dishonest testifier intentionally invents a fictional situation in imagination and bases her testimony on it. They can also arise when a testifier unintentionally misremembers or mis-imagines some scene, basing her testimony on an inaccurate representation. In both kinds of cases, we can still say that the listener’s imagining is based on the representation in the testifier’s mind (assuming the two mirror one another). However, the listener’s representation wouldn’t, in such a case, be based on the testifier’s knowledge, but instead on a misremembering or mere imagining. There’s thus a difference in the basis of such false testimonial belief compared to genuine testimonial knowledge.
[i] I say “includes” because I don’t mean for this view to rule out that the basis of the listener’s knowledge also includes facts about what the testifier asserted and her apparent reliability. It may be that this basis includes all the same things the first view said it did, while additionally also including the testifier’s knowledge.
[ii] I’m thus setting aside other kinds of testimony, including testimony about more abstract matters like the structure of a legal system or mathematical proof. Of course, a full account of the epistemology of testimony would have to give treatments of these kinds, too.
[iii] Of course, we’d never expect the representations in the minds of the two subjects to be exactly qualitatively identical with one another. Rather, we have to add some qualification about the extent to which the listener’s representation must mirror the testifier’s in order for successful knowledge transmission to occur. We might, for example, say that there are certain relevant respects in which the two must resemble one another, where perhaps what counts as “relevant” is determined by what information the testifier is trying to convey and other contextual factors.
References
Brown, Jessica. 2018. Fallibilism: Evidence and Knowledge. Oxford: Oxford University Press.
Hasson, Uri, Asif A. Ghazanfar, Bruno Galantucci, Simon Garrod, and Christian Keysers. 2012. "Brain-to-Brain Coupling: A Mechanism for Creating and Sharing a Social World." Trends in Cognitive Sciences 16 (2): 114-121.
Mar, Raymond A. 2004. "The Neuropsychology of Narrative: Story Comprehension, Story Production and their Interrelation." Neuropsychologia 42 (10): 1414-1434.
McClelland, James L., Felix Hill, Maja Rudolph, Jason Baldridge, and Hinrich Schütze. 2019. "Extending Machine Language Models Toward Human-Level Language Understanding." arXiv:1912.05877.
Silbert, L. J., C. J. Honey, E. Simony, D. Poeppel, and U. Hasson. 2014. "Coupled Neural Systems Underlie the Production and Comprehension of Naturalistic Narrative Speech." Proceedings of the National Academy of Sciences of the United States of America 111 (43): E4687-96.
Stephens, G. J., L. J. Silbert, and U. Hasson. 2010. "Speaker-Listener Neural Coupling Underlies Successful Communication." Proceedings of the National Academy of Sciences of the United States of America 107 (32): 14425-14430.
Zacks, Jeffrey M., Raymond A. Mar, and Navona Calarco. 2018. "The Cognitive Neuroscience of Discourse: Covered Ground and New Directions." In The Routledge Handbook of Discourse Processes, edited by Michael F. Schober, David N. Rapp and Anne M. Britt, 269-294. New York: Routledge.
Zadbood, Asieh, Janice Chen, Yuan Chang Leong, Kenneth A. Norman, and Uri Hasson. 2017. "How we Transmit Memories to Other Brains: Constructing Shared Neural Representations Via Communication." Cerebral Cortex 27 (10): 4988-5000.
Zwaan, Rolf A. 2016. "Situation Models, Mental Simulations, and Abstract Concepts in Discourse Comprehension." Psychonomic Bulletin & Review 23 (4): 1028-1034.
Zwaan, Rolf A. and Gabriel A. Radvansky. 1998. "Situation Models in Language Comprehension and Memory." Psychological Bulletin 123 (2): 162.