Attention and memory components in every-day cognitive problems in aging
- Iris Wiegand
- Jeremy M Wolfe
How do you know if you saw that? Electrophysiological correlates of searching through memory Trafton Drew1, Lauren H. Williams1, Jeremy M. Wolfe2, Iris Wiegand2,3 1 University of Utah 2 Brigham & Women’s Hospital 3 Max Planck UCL Centre for Computational Psychiatry and Ageing Research People are remarkably adept at recognizing thousands of previously studied pictures or objects (Brady et al., 2008). Wolfe (2012) extended this finding to the visual search domain by asking subjects to search for any instance of up to 100 memorized objects presented in a visual search display (“Hybrid search”). By varying both the number of objects held in memory and in the visual search array, he found that increasing the number of objects in visual space led to linear increase in response time (RT), whereas increasing the number of items in memory led to a logarithmic increase in RT. Although we know a great deal about the electrophysiological correlates of visual search, we know much less about memory search. In the current study, we sought to identify the electrophysiological correlates of memory search in a modified hybrid search task. During the learning phase, subjects (n=32) memorized a set of 2, 4, 16, or 64 real world objects and completed a subsequent recognition test. Next, subjects searched for the items in a lateralized search display. In order to identify the ERP components specific to searching through memory, the visual set size was constrained to a single lateralized object with a lateralized distractor. ERP waveforms were time-locked to the onset of the two-item search array. To examine recognition memory, we subtracted Absent from Present trials. We found a large modulation of N400 amplitude and latency (measured using fractional area latency) as a function of memory set: Larger memory set sizes were associated with a significantly smaller, later N400 deflection. While much prior research has shown that the N400 is sensitive to recognition of previously observed stimuli (e.g., Kutas & Federmeier, 2011), the current work suggests it may also be acutely sensitive to searching through memory spaces of different sizes. Acknowledgement: DOD: W911NF-07-2-0055 BSF: #2015301
In hybrid foraging tasks, observers search visual displays, so called patches, for multiple instances of any of several types of targets with the goal of collecting targets as quickly as possible. Here, targets were photorealistic objects. Younger and older adults collected targets by mouse clicks. They could move to the next patch whenever they decided to do so. The number of targets held in memory varied between 8 and 64 objects, and the number of items (targets and distractors) in the patches varied between 60 and 105 objects. Older adults foraged somewhat less efficiently than younger adults due to a more exploitative search strategy. When target items became depleted in a patch and search slowed down, younger adults acted according to the optimal foraging theory and moved on to the next patch when the instantaneous rate of collection was close to their average rate of collection. Older adults, by contrast, were more likely to stay longer and spend time searching for the last few targets. Within a patch, both younger and older adults tended to collect the same type of target in "runs." This behavior is more efficient than continual switching between target types. Furthermore, after correction for general age-related slowing, RT × set size functions revealed largely preserved attention and memory functions in older age. Hybrid foraging tasks share features with important real-world search tasks. Differences between younger and older observers on this task may therefore help to explain age differences in many complex search tasks of daily life. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
We tested younger and older observers’ attention and long-term memory functions in a “hybrid search” task, in which observers look through visual displays for instances of any of several types of targets held in memory. Apart from a general slowing, search efficiency did not change with age. In both age groups, reaction times increased linearly with the visual set size and logarithmically with the memory set size, with similar relative costs of increasing load (Experiment 1). We replicated the finding and further showed that performance remained comparable between age groups when familiarity cues were made irrelevant (Experiment 2) and target-context associations were to be retrieved (Experiment 3). Our findings are at variance with theories of cognitive aging that propose age-specific deficits in attention and memory. As hybrid search resembles many real-world searches, our results might be relevant to improve the ecological validity of assessing age-related cognitive decline.