Divided attention enhances explicit but not implicit conceptual memory: an item-specific account of the attentional boost effect

Attentional boost effect: research based on source memory and emotional materials

The attentional boost effect (ABE) refers to the phenomenon that stimuli which appear with targets in a detection task are better remembered than those that appear with distractors. Previous studies have consistently reported a robust ABE in item memory, but inconsistent conclusions have been drawn for source memory. Additionally, regarding the impact of emotional stimuli on the ABE, conclusions have also been inconsistent. The aim of this research was to clarify these inconsistencies. In Experiment 1, participants were asked to memorize different emotional background words (primary task), monitor the symbols above the words, press the spacebar when encountering the "+" (secondary task), and remember the size of the emotional background stimuli (as a source feature). Results revealed that the ABE of negative stimuli was stronger in item memory. For source memory, an ABE was observed only for large fonts. In Experiment 2, participants performed the same task as in Experiment 1, except for recalling the color of emotional stimuli instead of their size. Results indicated a stronger ABE for emotional stimuli in item memory, with no ABE observed in source memory. These findings suggest: (1) Item and source memory are regulated by distinct cognitive processes, leading to differential effects of emotionality on ABE in both types of memory. (2) Contrary to previous literature, emotional stimuli, such as negative words, do not consistently diminish the ABE.

The attentional boost effect in free recall dynamics

With the attentional boost effect (ABE), responding to a briefly presented target in a detection task enhances the encoding of other items presented at the same time. However, the effects of target detection on context memory for the event in which the stimulus appeared remain unclear. Here, we present findings from verbal free recall and recognition experiments that test the effects of target detection during encoding on temporal and relational aspects of context memory. Consistent with prior demonstrations of limited effects of target detection on context memory, in Experiment 1 there was no evidence that target detection influenced the likelihood of transitioning to items that were presented at similar times during encoding, or that were in the same encoding condition. These null effects were replicated in a second experiment, which added an old/new recognition and relational memory test. These results indicate that target detection during encoding has minimal effects on the formation of temporal associations between words in memory.

The effect of target detection on memory retrieval

Attention and memory are fundamental cognitive processes that closely interact. In the attentional boost effect (ABE), the stimuli that co-occur with targets are remembered better than those that co-occur with distractors in target detection tasks performed during memory encoding. In target detection tasks performed during retrieval, the stimuli that co-occur with targets are recognized as 'old' more easily than the stimuli that co-occur with distractors. This study mainly explored the internal mechanism of the effect of target detection on recognition. In Experiment 1, the full attention (FA; where participants performed only the memory task) condition was used to compare with divided attention (DA; where participants performed target detection while performing memory retrieval) condition to explore the impact of target detection and distraction inhibition on recognition. In Experiment 2, the proportion of old and new words in the retrieval stage was adjusted to 1:1 to eliminate the possible reaction tendency caused by the high proportion of old words. In Experiment 3, the presentation time of words was extended to 1.5 s and 3 s to eliminate the possible impact of rapid processing. The results indicated that the effect of target detection on recognition was attributed to both target detection and distraction rejection and is not affected by the ratio of old and new words and the word presentation time. The effect of target detection on recognition may be owing to temporal yoking of the dual tasks, which is different from the effect of target detection on memory encoding.

Exploring the roles of distinctiveness and performance anticipation in the Attentional Boost Effect

We tested the validity of two alternative accounts of the Attentional Boost Effect (ABE) - the finding that words associated with to-be-responded targets are recognized better than words associated with to-be-ignored distractors. The distinctiveness hypothesis assumes that, during recognition, participants probe their memories for distinctive information confirming that a word was studied (e.g., "I remember having pressed the spacebar, so I must have studied the word"). This strategy cannot be used in a between-subjects condition in which participants cannot appreciate the differences between target - and distractor-paired words. In agreement, Experiments 1A and 1B found that the ABE was significant in a within-subjects design, whereas it was eliminated in a between-subjects design. On the other hand, the performance anticipation hypothesis assumes that, during the study phase, participants anticipate the need of responding to a subset of target-paired words: this would create a persistent performance anticipation that would prevent them from effectively encoding distractor-paired words. In contrast with this account, we found that, when blocks of five distractor trials were regularly alternated with blocks of five target trials in Experiment 2, recognition accuracy decreased linearly in both conditions. Overall, these results suggest that distinctiveness, but not performance anticipation, might underlie the ABE.

Memory and attention: A double dissociation between memory encoding and memory retrieval

Research has found substantial negative effects of divided attention (DA) during encoding but less substantial effects when attention is divided during retrieval, an asymmetry which has been interpreted as indicating that different control processes or forms of attention are involved in encoding and retrieval (e.g., Chun & Johnson, 2011; Craik, Govoni, Naveh-Benjamin, & Anderson, 1996; Long, Kuhl, & Chun, 2018). The extant evidence, however, is not strong support for qualitative differences and might simply indicate differential sensitivity. The present experiments document a stronger, double dissociation by focusing on the Attentional Boost Effect (ABE) - a phenomenon in which the detection of targets in a secondary task enhances encoding of co-occurring stimuli. The dual-task interaction account proposes that the classical negative effects produced by dual-task interference are offset by a transient increase in externally-directed attention brought about by target detection. Since externally-directed attention is less valuable for retrieval processes, the ABE should result in a net negative effect when applied in the test phase because the dual-task interference would no longer be offset by the externally-directed boost occurring during target trials. Experiments 1, 2 and 4 confirmed the predictions by showing that test words paired with target stimuli were recognized significantly worse than test words paired with distractor stimuli. In contrast, Experiments 3 and 4 replicated the usual positive effects of the ABE with respect to encoding. We discuss these findings in light of recent theoretical proposals suggesting that encoding and retrieval processes are subserved by different forms of attention (external [perceptual] vs. internal [reflective]). Implications for the Transfer-Appropriate-Processing view of memory are also illustrated.

Can divided attention at retrieval improve memory? Effects of target detection during recognition

The attentional boost effect (ABE) is an improvement of memory under divided attention conditions in which stimulus encoding is enhanced when a target is detected in a simultaneous target-monitoring distracting task. Here we asked whether memory is similarly improved when the target-monitoring task occurs at the time of retrieval. In four experiments, participants encoded words under full attention then completed a recognition test under either divided attention, during which participants made recognition judgments while performing the target-monitoring task, or full attention, in which the target-monitoring task was not performed. Relative to distractor rejection, target detection increased hits and false alarms under divided attention with no net effect on discrimination. Targets and distractors had no effect on recognition under full attention. The target-related increase in hits and false alarms occurred regardless of whether the target-monitoring material matched or mismatched the test material and regardless of the target-to-distractor ratio and the target response. A change in bias accounts for the phenomenon, in which participants adopt a more lenient criterion for target-paired words than for distractor-paired words. The same divided attention manipulation that enhances memory at encoding does not similarly enhance memory at retrieval. Theoretical explanations are discussed.

The attentional boost effect facilitates visual category learning

Increasing evidence has shown that summary visual statistics, such as the mean size or centroid of locations, can be perceived without focal attention. Here, we tested the role of attention in visual category learning - rapid learning of visual similarities among paintings of the same artist. Participants encoded paintings from two famous artists into memory while simultaneously monitoring a rapid serial visual presentation (RSVP) stream of colored squares, pressing the spacebar for target colors and making no response to distractor colors. Paintings encoded with the RSVP targets were better remembered than those encoded with the RSVP distractors, demonstrating an Attentional Boost Effect. Importantly, pairing one artist's paintings with the RSVP targets led to better visual category learning - participants were more accurate at recognizing novel paintings from this artist, relative to another artist whose paintings were presented with the RSVP distractors. Thus, visual category learning is subjected to the same constraint of attention as exemplar memory, demonstrating common mechanisms for exemplar and category learning.

Grounding the Attentional Boost Effect in Events and the Efficient Brain

Attention and memory for everyday experiences vary over time, wherein some moments are better attended and subsequently better remembered than others. These effects have been demonstrated in naturalistic viewing tasks with complex and relatively uncontrolled stimuli, as well as in more controlled laboratory tasks with simpler stimuli. For example, in the attentional boost effect (ABE), participants perform two tasks at once: memorizing a series of briefly presented stimuli (e.g., pictures of outdoor scenes) for a later memory test, and responding to other concurrently presented cues that meet pre-defined criteria (e.g., participants press a button for a blue target square and do nothing for a red distractor square). However, rather than increasing dual-task interference, attending to a target cue boosts, rather than impairs, subsequent memory for concurrently presented information. In this review we describe current data on the extent and limitations of the attentional boost effect and whether it may be related to activity in the locus coeruleus neuromodulatory system. We suggest that insight into the mechanisms that produce the attentional boost effect may be found in recent advances in the locus coeruleus literature and from understanding of how the neurocognitive system handles stability and change in everyday events. We consequently propose updates to an early account of the attentional boost effect, the dual-task interaction model, to better ground it in what is currently known about event cognition and the role that the LC plays in regulating brain states.

The attentional boost effect facilitates the encoding of contextual details: New evidence with verbal materials and a modified recognition task

In the attentional boost effect (ABE), words or images encoded with to-be-responded targets are later recalled better than words or images encoded with to-be-ignored distractors. The ABE has been repeatedly demonstrated to improve item memory, whereas evidence concerning contextual memory is mixed, with studies showing both significant and null results. The present three experiments investigated whether the ABE could enhance contextual memory when using a recognition task that allowed participants to reinstate the original study context, by simultaneously manipulating the nature of the instructions provided at encoding. Participants studied a sequence of colored words paired with target (gray circles) or distractor (gray squares) stimuli, under the instructions to remember either the words and their colors (Exps. 1–2) or only the words (Exp. 3) and simultaneously press the space bar whenever a gray circle appeared on the screen. Then, after a brief interval, they were administered a modified recognition task involving two successive stages. First, participants were presented with two different words and had to decide which word was originally encoded; second, they were presented with five colored versions of the (correct) old words and had to remember the color in which they were studied. Results converged in showing that the ABE enhanced contextual memory, although the effect was more robust with intentional encoding instructions.

Concurrent target detection is associated with better memory for object exemplars

Under continuous dual-task conditions, participants show better memory for background information appearing at the same time as a response target in a concurrent task than for information appearing with a nontarget (the attentional boost effect, or ABE). While this effect has been demonstrated across a wide range of stimuli, few studies have examined the perceptual specificity of the memory difference. Here, we explored whether the ABE affects general category memory or perceptually specific exemplar memory. In an encoding phase, participants memorized images of objects presented in a continuous stream. At the same time, they pressed the space bar when a square appearing in the center of each image appeared in a target color, ignoring distractor-colored squares. The following four-alternative forced-choice memory test included the previously seen image, a perceptually distinct exemplar from the same category as the previously seen image, and two images from a new category. Regardless of whether images appeared during encoding three times (Experiment 1) or once (Experiment 2), participants recognized the correct exemplar more often during testing for images that had appeared with a target in encoding than for images that had appeared with a distractor. The difference in exemplar memory was not associated with a difference in false memories for within-category foils. This suggests that the ABE reflects modulation of perceptually detailed exemplar memory, which may be related to facilitation of pattern separation by detection-induced changes in cortical-hippocampal connectivity.

The Attentional Boost Effect in Young and Adult Euthymic Bipolar Patients and Healthy Controls

In the Attentional Boost Effect (ABE), stimuli encoded with to-be-responded targets are later recognized more accurately than stimuli encoded with to-be-ignored distractors. While this effect is robust in young adults, evidence regarding healthy older adults and clinical populations is sparse. The present study investigated whether a significant ABE is present in bipolar patients (BP), who, even in the euthymic phase, suffer from attentional deficits, and whether the effect is modulated by age. Young and adult euthymic BP and healthy controls (HC) presented with a sequence of pictures paired with target or distractor squares were asked to pay attention to the pictures and press the spacebar when a target square appeared. After a 15-min interval, their memory of the pictures was tested in a recognition task. The performance in the detection task was lower in BP than in HC, in both age groups. More importantly, neither young nor adult BP exhibited a significant ABE; for HC, a robust ABE was only found in young participants. The results suggest that the increase in the attentional demands of the detection task in BP and in adult HC draws resources away from the encoding of target-associated stimuli, resulting in elimination of the ABE. Clinical implications are discussed.

The attentional boost effect with semantic information detection tasks

The attentional boost effect (ABE) is a phenomenon in which in some dual tasks, increased attention to target detection causes an increase in memory performance related to items paired with the target. However, in previous studies concerning the ABE, the detection task objects usually reflected perceptual information. Whether the ABE could be observed if the task involves detecting semantic information is unclear. To answer this question, the present study adopted the classic dual-task paradigm of the ABE. Arabic numerals were used as semantic information stimuli in the detection tasks, and the degree of semantic processing in the detection task gradually increased over three experiments. The results showed that target detection with semantic information (i.e., digits) triggered the ABE (Experiment 1) and that the ABE was also generated under the semantic judgement-based detection task (i.e., odd-even detection task) regardless of whether the detection task used a single-target stimulus (Experiment 2) or a multi-target stimulus (Experiment 3). These findings indicate that an increased semantic load before the target decision in the detection task does not affect the ABE, and both perceptual detection and semantic detection can trigger the ABE.

The attentional boost effect enhances the recognition of bound features in short-term memory

In the Attentional Boost Effect (ABE), images or words encoded with unrelated to-be-responded targets are later remembered better than images or words encoded with to-be-ignored distractors. In the realm of short-term memory, the ABE has been previously shown to enhance the short-term recognition of single-feature stimuli. The present study replicated this finding and extended it to a condition requiring the encoding and retention of colour-shape associations. Across four experiments, participants studied arrays of four coloured squares (the colour-only condition), four gray shapes (the shape-only condition) or four coloured shapes (the binding condition), paired with either a target letter (to which participants had to respond by pressing the spacebar) or a distractor letter (for which no response was required). After a short delay, they were presented with a probe array and asked to decide whether it matched or not the encoded array. Results showed that, in all conditions, the recognition of target-paired arrays was significantly better than the recognition of distractor-paired arrays. These findings suggest that the ABE can enhance feature binding.

The role of distractor inhibition in the attentional boost effect: evidence from the R/K paradigm

Stimuli presented with targets in a detection task are later recognised more accurately than those presented with distractors, an unusual effect labelled the attentional boost effect (ABE). This effect may reflect an enhancement triggered by target detection, the inhibition of distractor rejection, or some combination of both. To test these possibilities, the present study adopted a baseline similar to that of Swallow and Jiang ([2014b]. The attentional boost effect really is a boost: evidence from a new baseline. Attention, Perception, & Psychophysics, 76(5), 1298-1307); the goal was to separate target-induced enhancements from distractor-induced inhibition. An R/K procedure was applied to further explore the kind of memory that might be affected by target detection or distractor rejection. The results show that the memory advantage for target-paired words was robust relative to that of baseline words; this advantage was mainly observed in R responses. More importantly, a memory reduction was also observed for distractor-paired words relative to baseline words, though this reduction was only observed in R responses. These data led us to conclude that the ABE was triggered by both processes: target-induced enhancement and distractor-induced inhibition. Moreover, both processes were more likely to affect recollection-based recognition.

Attending to behaviorally relevant moments enhances incidental relational memory

Memory for the items one has recently encountered is sometimes enhanced in divided attention tasks: Attending to behaviorally relevant items, such as a target in a detection task, boosts memory for unrelated background items (e.g., scenes or words). However, a central feature of episodic memory is memory for the spatiotemporal relationship between items and other elements of an event (relational memory), not just the item itself. Three experiments examined whether attending to a behaviorally relevant target-item boosts memory for the relationship between that item, its features, and a background scene. Participants memorized briefly presented scenes. At the same time, they pressed a button if a second unrelated item (a figure or face) was a particular target color (Experiments 1 and 2) or target gender (Experiment 3) rather than a distractor color or gender. Target and distractor items also varied in task-irrelevant features (shape, location, or facial identity). If attending to behaviorally relevant events influences relational memory, then participants should be better able to report both target-defining and irrelevant features of items that appeared with target-paired scenes rather than distractor-paired scenes. This was the case in all experiments: memory was enhanced for the target-paired scenes as well as the association between a scene and features of the paired target-item. Attending to behaviorally relevant moments therefore has broader effects on memory encoding than previously thought. In addition to boosting memory for unrelated background items, attending to targets facilitates relational memory in these tasks.