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ATTRIBUTE AND WORKING 1

Remembering More Than You Can Say: Re-Examining “Amnesia” of Attended

Attributes

Geoffrey W Harrisona, Melissa Kanga,b, Daryl E Wilsona

aDepartment of , Queen’s University, Kingston, Ontario K7L 3N6, Canada

bDepartment of Applied Psychology and Human Development, Ontario Institute for

Studies in , University of Toronto, Toronto, Ontario ON M5S 1V6, Canada

Word Count Total = 0

Corresponding Author: Geoffrey W. Harrison

Department of Psychology

Queen’s University

Kingston, Ontario K7L 3N6, Canada

Telephone: 1 (343) 333-3464

Email: [email protected]

Author Note

This research was supported by the National Sciences and Engineering Research

Council of Canada. Correspondence concerning this article should be addressed to

Geoffrey W. Harrison, Department of Psychology, Queen’s University, Kingston,

Ontario K7L 3N6, Canada. Email: [email protected] ATTRIBUTE AMNESIA AND 2

Abstract Attribute amnesia (AA) describes a phenomenon whereby observers fail a surprise memory test which asks them to report an attribute they had just attended and used to fulfil a task goal. This finding has cast on the prominent theory that results in into working memory (WM), to which two competing explanations have been proposed: (1) task demands dictate whether attended information is encoded into WM, and (2) attended information is encoded in a weak state that does not survive the demands of the surprise memory test. To address this debate our study circumvented the limitations of a surprise memory test by embedding a second search task within a typical color-based AA search task. The search task was modified so that the attended attribute would reappear in the second search as either the target, a distractor, or not at all. Critically, our results support encoding of the attended attribute in WM though to a weaker extent than the attribute that is required for report. A second experiment confirmed that WM encoding only occurs for the attended attribute, though distractor attributes produce a bias consistent with negative . Our data provide novel support for a theory of that links the strength of a memory’s representation with expectations for how it will be used in a task. Implications for the utility of this procedure in future investigations previously limited by single trial data

(i.e., surprise question methodology) are discussed.

Keywords: attribute amnesia, attention and memory, working memory, memory models

Declaration of interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ATTRIBUTE AMNESIA AND WORKING MEMORY 3

1.1 Introduction

Considerable work has established a strong link between attention and working memory (WM). Contemporary theories posit attention as the mechanism which selects information for entry into WM, and WM as an internal workspace for the and manipulation of internal representations to assist in goal directed behaviour. As such, attention is to have a positive relationship with memory consolidation, such that the more attention something is paid the better it will be represented in memory.

However, this characterization of the relationship between attention and WM was quickly shown to be incomplete. For example, phenomena such as (Simons &

Levin, 1997) and (Simons & Chabris, 1999) illustrate that we can be completely unaware of salient events (e.g., a gorilla appearing amongst player’s passing a ball) so long as that information falls outside our attentional purview. These results demonstrated that the benefits of attention come at a cost.

More recent work suggests even our of attention’s benefit for WM encoding may be incomplete. Across several studies, Chen and colleagues (2015a, 2015b,

2016a, 2016b, 2016c) revealed that even after directly attending to an object’s attribute

(e.g., its colour) observers can fail to accurately report the attended attribute during a surprise memory test. This occurs if the observer only uses the attended attribute in order to determine and report a separate attribute (e.g., its location). The authors named this phenomenon Attribute Amnesia (AA), and have argued that it is the expectation of later use of attended information that determines if information is encoded into WM.

Despite the generalizability of the AA phenomenon to various attended attributes and real-world situations (e.g., the color of a ball after tracking it for 30 ATTRIBUTE AMNESIA AND WORKING MEMORY 4 seconds; Chen et al., 2016), whether or not the attended attribute is truly absent from memory has been called into question. The basis of the criticisms against AA lies with three central methodological shortcomings. First, each participant contributes only a single response, due to the nature of a surprise memory test, offering limited data for interpretation. Second, the surprising nature of the surprise memory test may contribute to forgetting. Finally, the extended delay required to read and process the new instructions during the surprise memory test may contribute to memory failure through temporal decay. Taken together, the method used to assess memory consolidation of the attended attribute in AA paradigms may suffer from a lack of sensitivity hampering the detection of memory for the attended attribute.

In line with these criticisms, the first evidence of residual memory for the attended attribute in AA was demonstrated shortly after the initial discovery of the phenomenon. Performing a near direct replication of the AA paradigm, Jiang et al.,

(2016) showed that response times (RTs) for the to-be-reported attribute were facilitated when the attended attribute was repeated across trials. This is an effect known as repetition priming and clear evidence that some memory for the attended attribute is maintained across trials. As a result, the authors concluded that the attended attribute is initially robustly consolidated, but then transferred to a fragile state after it is no longer needed. In this fragile state, the authors argue that the attended attribute is susceptible to interference from novel events, like the surprise memory question, which leads to its failure to be accurately recalled. Wyble and Chen (2017) put forth an alternative explanation arguing that relevance of the attended attribute directly determines its strength when consolidated into memory. Thus, information not required for report is ATTRIBUTE AMNESIA AND WORKING MEMORY 5 only accessed and never consolidated into a robust form capable of being explicitly recalled. At present, the debate regarding the veracity of these two competing theories remains unresolved.

Fortunately, a methodology used to investigate the influence of robust WM representations on behaviour should be able to advance the debate surrounding the fate of attended attributes. Olivers and colleagues (2006, 2009) delineated the conditions which determine when an attribute held in WM will bias attention towards that attribute if it appears in a search display, with two findings important for our purposes. First, the memory attribute will only influence behaviour if the memory test is challenging enough that the attribute is robustly represented in WM.

Second, if the memory test is carried out before the search task, such that the attribute is no longer required to be held in WM, the attribute ceases to influence behaviour. Soto and Humphreys (2007) also demonstrated that merely instructing participants to attend to the attribute before performing a search task was not sufficient to elicit a memory matching search bias.

Thus, to further test the nature of the representation of attended items unavailable for explicit report, the present investigation implements a secondary singleton search task after the AA search but before the AA response. The embedded task design allows us to address the impact of the attended feature on behaviour after an abrupt change in context similar to the surprise question. Behaviour in the secondary search task can be assessed across many trials, resolving the criticism of limited data and sensitivity present in the traditional AA paradigm. Further, given that only features with robust representations in WM should bias attention in the secondary search task (Olivers ATTRIBUTE AMNESIA AND WORKING MEMORY 6 et al., 2006), any presence of the attended attribute from the AA search task influencing behaviour in the secondary search task will be evidence of a robust WM representation sustained across an abrupt change in context and task goals. Finally, by continuing both search tasks after the surprise memory test, this paradigm will allow for a direct comparison in the strength of attended attribute representations before and after they are required for report.

2.1 Experiment 1

2.2 Method

2.2.1 Participants

Thirty-two undergraduate students from Queen’s University participated in exchange for credit in an introductory psychology course. All had normal or corrected-to- normal vision and were naïve to the experiment’s purpose. A power analysis using

GPower* (Faul et al., 2007) determined a sample size of 32 would provide sufficient power to detect medium effect sizes. We replaced any participant’s data if they responded with less than 50% accuracy on any response type (replaced n = 6) or had overall RTs greater than 3 SD from the mean of participants (none replaced).

2.2.2 Apparatus

Participants completed the experiment on a personal computer in a testing room with the experimenter present. The experiment presented stimuli using Psychophysics

Toolbox version 3.0.8 (Brainard, 1997; Kleiner et al., 2007) in MATLAB version 7.04 on a 16-inch CRT monitor. Participants responded using a keyboard.

2.2.3 Design ATTRIBUTE AMNESIA AND WORKING MEMORY 7

The experiment consisted of two phases, within with each trial consisted of a shape-based search task embedded within a color-based search task. For the first phase (3 blocks of 60 trials each), participants completed three tasks in the following order: (1) color-based search task—searched for a uniquely colored letter and remembered its location for later report, (2) shape-based search task—performed a shape-based search for a diamond target amongst circles, and made a speeded response about the orientation of a line inside the diamond, and (3) color-based search location test—reported the location of the color-based search’s target letter. The second phase (3 blocks of 60 trials each) started on trial 181 and had the same procedure as the first phase except that before the location report task, participants completed a color report task (i.e., report the color of the target letter). Trial 181 is called the “surprise” trial and was then followed by 179 additional

“control” trials with the same procedure.

To determine whether the target letter’s color was encoded in memory, the shaped-based search had three conditions: (1) Target match—the color of the diamond target in the shape-based search was the same as the target letter’s color from the color- based search, (2) Distractor match—the color of one of the circle distractors in the shape- based search was the same as the target letter’s color from the color-based search, with the restriction that it could not be a circle directly adjacent to the target, (3) No match— the target letter’s color from the color-based search was not present in the shape-based search display (see Figure 1A). In all three conditions, the color of the distractor letters from the color-based search was never present in the shape-based search display. These three memory matching conditions occurred equally often with their order randomized. ATTRIBUTE AMNESIA AND WORKING MEMORY 8

Participants performed three separate 15 trial practice sessions. One for each of the color-based and shaped-based search tasks in isolation, and one for the two tasks combined. The experiment took approximately 50 minutes to complete.

Figure 1. Memory matching conditions for (A) Experiment 1 and (B) Experiment 2 for a color-based search trial with a red target and green distractors. Target Match refers to trials in the shaped-based search where the target’s color matched the color of either the target (Experiment 1) or distractor (Experiment 2) from the color-based search task. No Match refers to trials where no color from the color-based search appeared in the shaped- based search. Distractor Match refers to trials where one of the distractors’ colors in the shaped-based search matched the color of either the target (Experiment 1) or distractor (Experiment 2) from the color-based search task. 2.2.4 Procedure

See Figure 2 for a typical trial sequence. A central cross (1.2° x 0.9°) was presented at the beginning of each trial until the participant initiated the trial’s progression by pressing the spacebar. All stimuli were presented on a white background.

2.2.4.1 Color-based Search Task. The first search task was modeled after Chen and

Wyble’s (2015) Experiment 3, where participants searched for a uniquely colored letter in order to report its location. Four circles (1.2° diameter) were presented equidistant ATTRIBUTE AMNESIA AND WORKING MEMORY 9 from the fixation cross (9.2° diameter) for 300 ms and served as place holders for the upcoming search display items. The search items were presented for 400ms and were always the same four letters (A, B, D, E; font size 20) displayed equidistant from the fixation cross. For each trial, the target letter’s color was randomly selected from 8 possible colours (red [255 0 0], yellow [255 255 0], cyan [0 255 255], grey [127 127

127], green [25 200 25], blue [0 0 255], orange [255 127 0], pink [255 0 255]), and the distractor letters were all the same color randomly selected from the remaining colors.

Each letter was replaced with a mask for 400 ms that consisted of an ‘@’ symbol with four colored lines (colors chosen randomly from the of 8) overlaying the ‘@’ symbol in a hash-mark pattern. Participants remembered the location of the target letter for later report.

2.2.4.2 Shape-based Search Task. Immediately following the offset of the masks, the second search task was presented. The task was to report whether a line inside the diamond shaped target was oriented to the left or right of vertical using the left or right arrow keys, respectively. The shape-based search task consisted of 5 circles (1.8° diameter) and one diamond (2.1° side length) each filled with a unique color and a line

(0.5° length) oriented 45° left or right from vertical. The shapes were equidistant from a central fixation cross forming a circular display (9.2° diameter). The display remained present for 3000 ms or until response. If participants responded faster than 3000 ms, a blank screen was presented for the remaining interval.

2.2.4.3 Color-based Search Memory Test. Following the shape-based search, participants were tested for their memory of either the target letter’s location only (first

180 trials) or both the target letter’s color and its location (second 180 trials). For the 180 ATTRIBUTE AMNESIA AND WORKING MEMORY 10 trials before the surprise memory test for color (pre-surprise trials), the location response screen displayed (font size 20): “Press a corresponding number to indicate the ‘Location’ of the target letter”. Below the text, the numbers 1-4 (font size 40) were displayed overlaying the locations of the color-based search items. For the surprise memory test for color and the remaining 179 trials (post-surprise trials) both color and location of the target letter were tested. The color response screen displayed: “This is a surprise memory test! Here we test the colour of the target letter. Press a corresponding number to indicate the "Colour" of the target letter”. Below the text, the numbers 1-8 were presented in two columns beside rectangles (0.5° x 2.5°) of each of the possible colors described above.

After this response, the location memory test screen was presented. ATTRIBUTE AMNESIA AND WORKING MEMORY 11

Figure 2. An example trial sequence for Experiments 1 and 2. Note that the distractor colour, not target colour, from the color-based search could reappear in the shape-based search in Experiment 2. ATTRIBUTE AMNESIA AND WORKING MEMORY 12

2.3 Results

2.3.1 Color-based Search Analysis

During Pre-Surprise trials, mean location report accuracy for the target letter was

97.4%. Thus, participants could use color to locate the target letter and easily maintain it throughout the shape-based search. On the first trial that included the surprise memory test (the surprise trial) 25% of participants (8 out of 32) were able to report the target letter’s color. Memory for the uniquely colored target letter improved significantly on the first control trial to 71.9%, χ2(1) = 11.53, p = .001, φ = 0.60. Color accuracy remained high for the remainder of the Post-Surprise trials (M = 91.9%). Location accuracy was slightly lower on the surprise trial (59.4%) than on the first control trial (87.5%), χ2(1) =

5.82, p = .016, φ = 0.43, but accuracy remained high for the remainder of the Post-

Surprise trials (M = 93.4%). These results demonstrated a replication of attribute amnesia for color on the surprise trial and showed that both target attributes could be maintained for report throughout the second search task with no cost to performance.

2.3.2 Shape-based Search Analysis

RTs were only analyzed for trials in which both search tasks were performed accurately. Mean accuracy for the singleton search task was 97.5%. A Trial Time (Pre-

Surprise, Post-Surprise) x Memory Match (Target Match, Distractor Match, No Match) repeated measures analysis of variance (rmANOVA) was conducted on mean RTs (see

Figure 3). The ANOVA revealed a main effect of Trial Time, F(1,31) = 11.59, p = .002, partial η2 = .27, a main effect of Memory Match, F(2,62) = 103.25, p < .001, partial η2

= .77, and a significant interaction, F(2,62) = 50.69, p < .001, partial η2 = .62. ATTRIBUTE AMNESIA AND WORKING MEMORY 13

Figure 3. Mean RTs for the shape-based singleton task in Experiment 1. Error bars represent the mean square error of the Trial Time x Memory Match interaction term. To follow up the significant interaction, we ran separate ANOVAs for Pre- and

Post-Surprise trials. For Pre-Surprise trials, there was a main effect of Memory Match,

F(2,62) = 8.73, p < .001, partial η2 = .22. Two planned t-tests revealed faster RTs for the

Target Match condition (M = 0.796, SEM = 0.03) compared to the No Match condition

(M = 0.814, SEM = 0.03), t(31) = 2.40, p = .02, d = 0.42, and slower RTs for the

Distractor Match condition (M = 0.829, SEM = 0.03) compared to the No Match condition, t(31) = 2.15, p = .04, d = 0.38. For post-surprise trials, there was again a main effect of Memory Match, F(2,62) = 90.55, p < .001, partial η2 = .75. The same set of planned t-tests revealed the same RT pattern but larger effect sizes, such that RTs in the

Target Match condition (M = 0.759, SEM = 0.03) were faster than in the No Match condition (M = 0.906, SEM = 0.04), t(31) = 9.20, p < .001, d = 1.63, and RTs in the

Distractor Match condition (M = 0.978, SEM = 0.04) were slower than in the No Match ATTRIBUTE AMNESIA AND WORKING MEMORY 14 condition, t(31) = 5.02, p < .001, d = 0.89. Figure 4 summarizes these results in terms of search biases relative to the No Match condition.

Figure 4. Effect of the color-based search’s target’s color matching either the Target or Distractor item in the shape-based search. Search bias is the difference in mean RT of each condition subtracted from the No Match condition. Error bars represent the 95% confidence intervals of the comparisons. 2.4 Discussion

Consistent with the attended attribute being held in WM, we found that search behaviour during the shape-based search task was facilitated if the attended attribute (i.e., target color) from the color-based search task matched the color of the shape-based search target, and hindered if the attended attribute reappeared as the color of one of the shape-based search distractors. This respective speeding and slowing of RTs was magnified for the Post-Surprise trials when the color became required for report. This finding partially supports Wyble and Chen’s (2017) hypothesis of weaker memory consolidation for attributes deemed non-essential for report. However, their theory does not accommodate the fact that these representations are still consolidated into WM ATTRIBUTE AMNESIA AND WORKING MEMORY 15 representations, a robust form of WM capable of influencing behaviour in entirely new contexts. This finding casts doubt on Jiang and colleagues’ (2016) theory that after serving its purpose of identifying the to-be-reported attribute, the attended attribute is relegated to such a weak state that it is susceptible to overwriting from new information or contexts.

Interestingly, in another study by Chen et al., (2016) participants were unable to report the color of a ball they had been attending to for up to one minute, but the majority of incorrect responses were made to the color of the distractor ball. The authors proposed that the AA search task encodes all processed colors (i.e., target and distractors) into an accessory state of memory (e.g., LTM; Oberauer, 2002) whereas only the to-be-reported attribute is encoded into WM. Our results show that, though in a weaker form, the attended attribute is still represented in a non-accessory state of WM capable of influencing search behaviour.

However, it may be possible that attentional selection mechanics in the color- based search task lead to encoding of both target and distractor colors and either of these representations are sufficient to bias search performance in the shape-based search task.

To address this issue, we ran a second experiment to ensure our pattern of results was specific to the target color from the color-based search task. Specifically, instead of manipulating the match between the target color from the color-based search task and items from the shape-based search task (target, distractor, or none), we manipulated whether the distractor color from the color-based search task matched items from the shape-based search task (target, distractor, or none).

3.1 Experiment 2 ATTRIBUTE AMNESIA AND WORKING MEMORY 16

It was unclear whether the RT speeding and slowing found in Experiment 1 was specific to the target color from the color-based search task, or if attentional selection mechanisms during the color-based search task could produce similar RT effects in the shape-based search task for the inhibited distractor color. Therefore, in Experiment 2, we manipulated whether the distractor color from the color-based search task matched items from the shape-based search task (target, distractor, none).

3.2 Method

3.2.1 Participants

Thirty-two undergraduate students from Queen’s University participated in exchange for credit in an introductory psychology course. All had normal or corrected-to- normal vision and were naïve to the experiment’s purpose. The predetermined sample size was set at thirty-two for the same as in Experiment 1. We replaced any participant’s data if they responded with less than 50% accuracy on any response type

(none replaced) or had overall RTs greater than 3 SD from the mean (replaced n = 2).

3.2.2 Apparatus, Design and Procedure

The apparatus, design and experimental procedure for Experiment 2 were the same as Experiment 1 except for what constituted each of the memory matching conditions. Instead of the target letter’s color from the color-based search, the distractor letters’ color matched either the target’s or a distractor’s color or neither in the shape- based search task (see Figure 1B).

3.3 Results

3.3.1 Color-based Search Analysis ATTRIBUTE AMNESIA AND WORKING MEMORY 17

During Pre-Surprise trials, location report accuracy for the target letter was 97%.

Surprise trial memory performance was 6.3%; 2 of 32 participants were able to report the target letter’s color. Performance on the memory test for color rose significantly to 62.5% by the first post-surprise trial, χ2(1) = 14.45, p < .001, φ = 0.67, and was 92.5% for all

Post-Surprise trials. Location accuracy on the Surprise trial dropped to 50%, but rose significantly by the next trial to 93.8%, χ2(1) = 12.07, p = .001, φ = 0.61, and was 93.7% for all Post-Surprise trials. These results once again replicated attribute amnesia for color on the Surprise trial and showed that both target attributes could be maintained for report throughout the second search task with minimal cost.

3.3.2 Shape-based Search Analysis

RTs were only analyzed for trials in which both search tasks were performed accurately. Mean accuracy for the shape-based search task was 97.5%. The same Trial

Time (Pre-Surprise, Post-Surprise) x Memory Match (Target Match, Distractor Match,

No Match) rmANOVA was conducted on mean RTs as in Experiment 1 (see Figure 5).

The ANOVA revealed a main effect of Memory Match, F(2,62) = 3.82, p = .03, partial η2

= .11, a marginally significant effect of Trial Time, F(1,31) = 3.83, p = .06, partial η2

= .11, such that RTs for Post-Surprise trials (M = 0.813, SEM = 0.027) were slightly slower than Pre-Surprise trials (M = 0.796, SEM = 0.025), and a non-significant interaction, F(2,62) = 0.51, p = .95, partial η2 < .01. ATTRIBUTE AMNESIA AND WORKING MEMORY 18

Figure 5. Mean RTs for the shape-based singleton task in Experiment 2. Error bars represent the mean square error of the Memory Match main effect term. To follow up the main effect of Memory Match, we ran two paired t-tests for the three memory match conditions collapsing across Trial Time. The Target Match condition (M = 0.810, SEM = .027) was significantly slower than the No Match condition

(M = 0.794, SEM = .025), t(31) = 2.19, p = .04, d = 0.39, and the Distractor Match condition (M = 0.808, SEM = .03) was also slower than the No Match condition, t(31) =

2.32, p = .03, d = 0.41.

Though the interaction between Memory Match and Trial Time was not significant, we ran the same set of separate ANOVAs and t-tests as in Experiment 1 for the purposes of making more direct comparison across experiments. For Pre-Surprise trials, there was no effect of Memory Match, F(2,62) = 1.68, p = .20, partial η2 = .05.

Two planned t-tests revealed no differences between RTs for the Target Match condition

(M = 0.801, SEM = 0.03) compared to the No Match condition (M = 0.787, SEM = 0.03), t(31) = 1.51, p = .14, d = 0.27, or between the Distractor Match (M = 0.799, SEM = 0.03) ATTRIBUTE AMNESIA AND WORKING MEMORY 19 and No Match conditions, t(31) = 1.38, p = .18, d = 0.24. For post-surprise trials, there was also no main effect of Memory Match, F(1.49,46.22) = 2.11, p = .14, partial η2 = .06.

Planned t-tests revealed no difference between the Target Match condition (M = 0.820,

SEM = 0.03) and the No Match condition (M = 0.802, SEM = 0.03), t(31) = 1.61, p = .12, d = 0.28, however RTs in the Distractor Match condition (M = 0.978, SEM = 0.04) were slower than in the No Match condition, t(31) = 5.02, p < .001, d = 0.89. Figure 6 summarizes these results in terms of search biases relative to the No Match condition.

Figure 6. Effect of the color-based search’s distractor’s color matching either the Target or Distractor item in the shape-based search. Search bias is the difference in mean RT of each condition subtracted from the No Match condition. Error bars represent the 95% confidence intervals of the comparisons. 3.4 Discussion

Somewhat surprisingly, the inhibited distractor color from the AA search did influence search behaviour in the shape-based search task, though not in a way consistent with its encoding in WM. Namely, regardless of its reappearance as the target or distractor in the shape-based search task, the mere presence of the AA search’s distractor ATTRIBUTE AMNESIA AND WORKING MEMORY 20 color produced slower RTs compared to when it did not reappear. This finding is less surprising when attributed to an effect known as (May et al., 1995;

Tipper, 1985; see Frings et al., 2015 for a recent review). Negative priming describes how previously ignored attributes can impair one’s ability to identify them if they reappear on subsequent trials. Though originally considered a phenomenon arising from attentional selection mechanisms, more recent accounts acknowledge contributions from both attention and memory processes in the negative priming phenomenon (Mayr &

Buchner, 2007). The memory mechanism responsible for governing negative priming is thought to be an implicit or accessory memory storage system, both of which have been proposed as potential storage systems for the AA search’s target color (e.g., Jiang et al.,

2016; Chen et al., 2016). However, when we compared the pattern of search biases from

Experiments 1 and 2 directly we found a clear divergence that further underscores our conclusion from Experiment 1 that the attended attribute is stored not implicitly or in an accessory state, but in the more robust and privileged WM system.

4.1 General Discussion

Shortly after Chen and colleagues (2015a,b) demonstrated that participants fail to report an attended object’s feature if they don’t believe they will be required to report it,

Jiang and colleagues (2016) qualified this failure of by showing that the attribute persisted across trials in a form of evidenced by . This highlighted the lack of sensitivity in using a single surprise question to evaluate the robustness with which the attended attribute is consolidated into memory and led to two competing theories concerning the attribute’s mnemonic fate. We directly addressed these questions by examining the extent to which the attended attribute biased ATTRIBUTE AMNESIA AND WORKING MEMORY 21 search performance in a second shape-based search task commonly used to examine the influence of WM items on search behaviour. Performance on this shape-based search task was gathered over many trials and allowed us to directly compare the attended attribute’s representation in WM before and after it was required for report.

Before the attended attribute was required for report, shape-based search RTs were fastest when the target color of the color-based search task matched the target and slowest when it matched a distractor, a pattern of influence on search behaviour which has been shown to be specific to items consolidated into a robust WM representation.

This bias in search performance was found despite disruption of sensory persistence by visual masks and the change in search context and settings to achieve the search goal. The search bias was also present despite the replication of participants’ failure to explicitly report the attended attribute on a surprise memory test. Finally, when the attended attribute was also reported at the end of the trial, the bias in search performance was the same as before but in a magnified form.

In Experiment 2, the distractor color from the color-based search task was reintroduced in the shape-based search task in order to address the alternative explanation that attentional selection mechanisms (both attending the target and inhibiting the distractor attribute) were sufficient to produce the pattern of search bias observed in

Experiment 1. The same pattern of search bias was not observed; however, across all trials there was a significant search bias consistent with the reappearance of the AA’s distractor color producing negative priming. In a unique variation of the AA paradigm,

Chen and Wyble (2016) found that when tracking one of two colored balls for several seconds nearly all participants reported one of the two colors but still made errors about ATTRIBUTE AMNESIA AND WORKING MEMORY 22 which one was the target. The authors attributed this behaviour to both attributes in AA paradigms being represented in an accessory memory system, one of the memory systems putatively responsible for producing negative priming (Mayr & Buchner, 2007). Our results, showing a stark divergence in the search bias profiles during the shape-based search task for the reappearance of target compared to distractor colors from the color- based search, clearly demonstrate distinct mnemonic fates for these two items.

Our findings clearly show that attended attributes not available for explicit report are still consolidated in WM to a degree sufficient enough to influence behaviour even after considerable changes to context and task goals. Therefore, in contrast to Jiang and colleagues’ (2016) theory, they are not reduced to such a fragile state that new information overwrites them. In partial support of Wyble and Chen’s (2017) theory, the relevance of the attended attribute did directly influence its encoding strength, as evidenced by the magnification of search bias once participants had to report it as well.

However, they also stated that the attended attribute in a traditional AA paradigm is

“merely accessed without being consolidated” (Wyble and Chen, 2017, p. 999), so extant theories must be modified in order to explain our results.

By introducing a secondary search task into a traditional AA paradigm, we were able to overcome the significant limitations posed by single trial data gathered from a surprise memory test. Data from the second search task provides a rich opportunity for future studies to further investigate the fate of attended attributes no longer necessary for report, including the potential to examine the consequences of individual differences in search bias strength. Finally, our novel approach leads to more sensitive indexing of the mnemonic fate of information that observers only briefly make use of, a nascent area of ATTRIBUTE AMNESIA AND WORKING MEMORY 23 research that has only begun to receive laboratory attention but closely approximates the varied demands to memory and dynamic changes in context often seen in daily life. ATTRIBUTE AMNESIA AND WORKING MEMORY 24

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