The tradeoff between item and order information in short-term memory does not depend on encoding time

Abstract

Participants can optimize encoding of an immediate verbal memory test for item or for order information, or they can try to be ready for either type of test. Dividing encoding between both kinds of information, however, comes at a cost. Recently, it has been shown that the cost is more severe for order information compared to item information (Guitard et al., 2022). Here, for the first time, we evaluated which factor can better account for this asymmetry by contrasting two hypotheses. According to a rate hypothesis, divided attention affects the rate of encoding more for order than for items. According to an alternative, asymptote hypothesis, divided attention does not affect the rates but diminishes the endpoint, or asymptotic level, of order encoding more than item encoding. In three experiments to distinguish these hypotheses, participants prepared for an item fragment completion test, an order reconstruction test, or both types of tests, in trials with different durations of presentation. Overall, our results were better accounted for by a model which assumes that dividing attention between preparation for item and order testing affects the asymptote of encoding more for order than for items, with no effects on the rates of order or item encoding compared to preparation for a single test. The findings not only replicate our prior results, but also demonstrate that the allocation of attention to item or order processing can be disentangled from the time on task. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Figure 1. Illustration of the predictions derived from two major time-related possibilities (rate, asymptote) as a function of attentional condition (50, 100), memory test (order test, item test), and presentation time of the items.

Note. Rate (left panels): divided attention affects the rate of encoding more for order than for items. Asymptote (right panels): the divided attention affects the asymptote of encoding more for order than for items.

Figure 2

Illustration of the procedure used in Experiment 1, adapted from Guitard et al. (2022), for when participants prepare for an item test (A) and when they prepare for either an item or an order test, with the test unknown until after the list presentation (B). Not shown: conditions in which participants prepare only for an order test.

Figure 3. Proportion of correct response as a function of attentional condition (50, 100) memory test (order test, item test), and presentation time of the items (500 ms, 1000 ms, 2000 ms) in Experiment 1.

Note. Left two columns, serial positions (1–6); right two columns, results averaged across serial positions. Error bars represent 95% within-participant confidence intervals computed according to Morey’s (2008) procedure. 50: 50% of the trials were an order test and 50% of the trials were an item test; 100: 100% of the trials were an order test (or 100% of the trials were an item test).

Figure 4. Proportion of correct response as a function of attentional condition (50, 100) memory test (order test, item test), and presentation time of the items (500 ms, 1000 ms, 3000 ms) in Experiment 2.

Note. Left two columns, serial positions (1–6); right two columns, results averaged across serial positions. Error bars represent 95% within-participant confidence intervals computed according to Morey’s (2008) procedure. 50: 50% of the trials were an order test and 50% of the trials were an item test; 100: 100% of the trials were an order test (or 100% of the trials were an item test).

Figure 5. Proportion of correct response as a function of attentional condition (50, 100) memory test (order test, item test), and presentation time of the items (250 ms, 500 ms, 1500 ms, 3000 ms) in Experiment 3.

Note. Left two columns, serial positions (1–6); right two columns, results averaged across serial positions. Error bars represent 95% within-participant confidence intervals computed according to Morey’s (2008) procedure. 50: 50% of the trials were an order test and 50% of the trials were an item test; 100: 100% of the trials were an order test (or 100% of the trials were an item test).

Figure 6. Non-linear Bayesian model predictions for each model (rate model, asymptote model, hybrid model) and proportion of correct response as a function of the attentional condition (50, 100), the memory test (order test, item test), and the presentation time of the items (500 ms, 1000 ms, 2000 ms) in Experiment 1.

Note. Error bars represent 95% within-participant confidence intervals computed according to Morey’s (2008) procedure. The solid and dashed lined represents the average prediction of each model and the shading corresponds to 95% highest density intervals of the models.

Figure 7. Non-linear Bayesian model predictions for each model (rate model, asymptote model, hybrid model) and proportion of correct response as a function of the attentional condition (50, 100), the memory test (order test, item test), and the presentation time of the items (500 ms, 1000 ms, 3000 ms) in Experiment 2.

Note. Error bars represent 95% within-participant confidence intervals computed according to Morey’s (2008) procedure. The solid and dashed lined represents the average prediction of each model and the shading corresponds to 95% highest density intervals of the models.

Figure 8. Non-linear Bayesian model predictions for each model (rate model, asymptote model, hybrid model) and proportion of correct response as a function of the attentional condition (50, 100), the memory test (order test, item test), and the presentation time of the items (250 ms, 500 ms, 1500 ms, 3000 ms) in Experiment 3.

Note. Error bars represent 95% within-participant confidence intervals computed according to Morey’s (2008) procedure. The solid and dashed lined represents the average prediction of each model and the shading corresponds to 95% highest density intervals of the models.

Figure 9

Cognitive load functions for all three experiments, assuming 500 ms for word perception and equally divided time between item and order in the dual-attention conditions.