Working memory and focal attention

Abstract

Measures of retrieval speed indicated that only a small subset of representations in working memory falls within the focus of attention. An n-back task, which required tracking an item 1, 2, or 3 back in a sequentially presented list, was used to examine the representation and retrieval of recent events and how control processes can be used to maintain an item in focal attention while concurrently processing new information. A speed-accuracy trade-off procedure was used to derive measures of the availability and the speed with which recent events can be accessed. Results converge with other time course studies in demonstrating that attention can be concurrently allocated only to a small number of memory representations, perhaps just 1 item. Measures of retrieval speed further demonstrate that order information is retrieved by a slow search process when an item is not maintained within focal attention.

Figure A1

Average $d_{\mathrm{FA}}^{\prime }$ scaling of the false-alarm rates for 1-back, 2-back, and 3-back list lures as a function of processing time (lag of the response cue plus latency to respond to the cue) in Experiment 1. Smooth curves show the best fits of the dual-process model (Equation A1).

Figure A2

Average $d_{\mathrm{FA}}^{\prime }$ scaling of the false-alarm rates for 1-back exclusion, 2-back exclusion, and 4-back exclusion list lures as a function of processing time (lag of the response cue plus latency to respond to the cue) in Experiment 2. Smooth curves show the best fits of the dual-process model (Equation A1).

Figure 1

Schematic illustration demonstrating how the speed and accuracy of retrieval, measured by the response-signal speed–accuracy trade-off (SAT) procedure, vary with recency. As more time and items are interpolated between study and test, the availability of a memory representation decreases continuously, engendering lower levels of asymptotic accuracy. In contrast, retrieval speed shows a dichotomous pattern: Retrieval speed (SAT intercept and rate) is constant across all serial positions except the last unit processed (recency = 1), which can be accessed 50% faster than all other representations.

Figure 2

Sample trial sequence illustrating the speed—accuracy trade-off (SAT) variant for the n-back task used in Experiment 1.

Figure 3

Average d′ accuracy (symbols) as a function of processing time (lag of the response cue plus latency to respond to the cue) for the 1-back, 2-back, and 3-back conditions in Experiment 1. Smooth curves show the best fits of Equation 1 with the (average) parameters listed in Table 1.

Figure 4

Top panel: Best fit of a pure backward-search model to the average d′ data from Experiment 1. Bottom panel: Best fit to the average d′ data from Experiment 1 with a mixture of a backward search and a direct match to focal attention using the (average) parameters listed in Table 2.

Figure 5

Average d′ accuracy (symbols) as a function of processing time (lag of the response cue plus latency to respond to the cue) for the 1-back, 2-back, and 3-back inclusion conditions and the 3-back exclusion condition in Experiment 2. Smooth curves show the best fits of Equation 1 with the (average) parameters listed in Table 3.

Figure 6

Best fit to the average d′ data from Experiment 2 with a mixture of a backward search and a direct match to focal attention using the (average) parameters listed in Table 4.