- It is well-known that to be able to categorize an item (e.g., a car), we need recognition memory of the item.
- New research indicates that our perceptual capacities may also depend on recollections of our individual past experiences.
- Recollections of our individual past experiences may improve our perceptual capacities by fine-tuning categories in our recognition memory.
- These new findings are surprising, as many studies have shown that recollections of our individual past experiences often are highly unreliable.
If you look at your surroundings, you see various objects scattered around them. Perhaps you have just made yourself a café latte, which now sits in front of you on your sofa table. As you direct your attention towards it, you notice the shape of the mug and the color and texture of the milk foam. Looking further around on your sofa table, you may spot various other items: your cell phone, car keys, sunglasses, a remote control, a sports magazine.
It has long been known that the objects we are able to see depend in part on the categories that are stored in our long-term memory (e.g., Brogaard & Sørensen, in press a). However, new research simulating human perception and memory suggests that which objects we are able to see also depends on memories of our individual past experiences (Görler et al., 2020; Brogaard & Sørensen, in press a).
Recognition Memory and Memory Templates
For you to be able to see things such as keys, phones, glasses, or magazines, light must first reach the retina in your eye, then the early visual system in the back of your brain. At later stages of visual processing, the visual information needs to get sorted through recognition memory.
Recognition memory consists of category-specific templates for determining the identity of what you are looking at in your surroundings (Brogaard & Sørensen, in press a, in press b). If the brain weren't equipped with recognition memory containing the right sorts of templates for object identification, you wouldn't be able to see an object in your environment as a specific kind of object, such as a mug, a phone, or a key.
Recognition memory is only one form of long-term memory. It's relatively unsurprising that our ability to visually identify and distinguish between distinct items in our surroundings depends on this kind of long-term memory.
What's more surprising is that our capacities for object identification and discrimination also appear to depend on a type of long-term memory known as episodic memory.
Episodic memory is that part of long-term memory that enables you to remember what you have experienced in the past, say scraping ice off your car windows this morning, buying a new cell phone last Sunday, or tripping on your gown at your high school graduation.
Psychologist Endel Tulving (1972) compared episodic remembering to mental time travel, allowing you to be a "fly on the wall" in the life of your younger self and "re-experience" episodes from your past.
Injuries to Memory Areas in the Brain Can Compromise Perception
A substantial body of research has shown that people who have damaged areas of the brain associated with episodic memory (e.g., the hippocampus and perirhinal cortex) partially lose the ability to visually discriminate between scenes, faces, and objects—especially objects with a lot of features in common (Lee et al., 2005; Graham et al., 2010; Barense et al., 2011; O'Neil et al., 2013; Inhoff et al., 2019).
Earlier studies looked at people whose lesions to memory areas in the brain partially overlapped with nearby areas in the visual system. So, the older studies couldn't rule out that the impaired visual capacities were due to the damages to the visual system rather than to the damages to the memory system. But more recent studies have found impaired visual perception in people with brain lesions that were highly specific to areas in the brain associated with episodic memory (e.g., Inhoff et al., 2019).
It is still unclear how episodic memory can make a difference to our perceptual capacities. One hypothesis is that when we recall episodes from our past, the replay of what we experienced in the past can help fine-tune the templates we use to visually categorize objects into, say, cups, keys, or televisions.
New Research of the Effects of Episodic Memory on Perception
Using machine learning to simulate visual perception and episodic memory in humans, Görler and colleagues recently investigated this hypothesis. After a learning phase that mimicked human perception and encoding of perceptual information in episodic memory, the researchers tested the computer simulation's ability to visually distinguish between objects.
The data showed that the more times the computer simulation had replayed information encoded in episodic memory, the better the system performed on visual discrimination tasks.
According to Görler and colleagues, a plausible interpretation of these findings is that the "replay" of episodic memories helps fine-tune the memory templates we use to categorize objects. As fine-tuned memory templates can help us tell apart objects in our surroundings, recalling episodes from our past can thus help improve our perceptual capacities.
This raises an intriguing question: If episodic memory is notoriously unreliable, as many studies have shown (e.g., Loftus, & Hoffman, 1989), how can recall of epistemic memories help improve our perceptual capacities? (cf. Brogaard & Sørensen, in press a). We will turn to that question in the next post.
Barense, M. D., Henson, R. N., & Graham, K. S. (2011). Perception and conception: temporal lobe activity during complex discriminations of familiar and novel faces and objects. Journal of Cognitive Neuroscience, 23(10), 3052-3067.
Brogaard, B., & Sørensen, T. A. (in press a). The Role of Long-Term Memory in Visual Perception. In R. French & B. Brogaard, The Roles of Representation in Visual Perception. Springer Publishing Company.
Brogaard, B., & Sørensen, T. A. (in press b). Perceptual variation in object perception: A defense of perceptual pluralism. In A. Mroczko-Wąsowicz & R. Grush (eds.), Sensory individuals: Contemporary perspectives on modality-specific and multimodal perceptual objects, Oxford: Oxford University Press.
Brogaard, B., & Sørensen, T. A. (in press c). Predictive processing and object recognition. In T. Cheng & J. Hohwy (eds.), Expected experiences: The predictive mind in an uncertain world, New York: Routledge.
Graham, K. S., Barense, M. D., & Lee, A. C. H. (2010). Going beyond LTM in the MTL: a synthesis of neuropsychological and neuroimaging findings on the role of the medial temporal lobe in memory and perception. Neuropsychologia, 48, 831-853.
Görler, R., Wiskott, L., & Cheng, S. (2020). Improving sensory representations using episodic memory. Hippocampus, 30(6), 638-656.
Inhoff, M. C., Heusser, A. C., Tambini, A., Martin, C. B., O’Neile, E. B., Köhler, S., et al. (2019). Understanding perirhinal contributions to perception and memory: Evidence through the lens of selective perirhinal damage. Neuropsychologia, 124(18), 9-18.
Lee, A. C. H., Fischer, T. J., Murray, E. A., Saksida, L. M., Epstein, R. A., Kapur, N., et al. (2005). Perceptual deficits in amnesia: Challenging the medial temporal lobe “mnemonic” view. Neuropsychologia, 43(1), 1-11.
Loftus, E. F., & Hoffman, H. G. (1989). Misinformation and memory: The creation of new memories. Journal of Experimental Psychology: General, 118(1), 100-104.
O’Neil, E. B., Barkley, V. A., & Köhler, S. (2013). Representational demands modulate involvement of perirhinal cortex in face processing: representational demands modulate perirhinal cortex. Hippocampus, 23, 592-605.
Tulving, E. (1972). Episodic and semantic memory. In E. Tulving, & W. Donaldson (eds.), Organization of Memory, Academic Press, 381-403.