Visual imagery influences attentional guidance during visual search: Behavioral and electrophysiological evidence

Visual mental imagery of nonpredictive central social cues triggers automatic attentional orienting

Previous research has demonstrated that social cues (e.g., eye gaze, walking direction of biological motion) can automatically guide people's focus of attention, a well-known phenomenon called social attention. The current research shows that voluntarily generated social cues via visual mental imagery, without being physically presented, can produce robust attentional orienting similar to the classic social attentional orienting effect. Combining a visual imagery task with a dot-probe task, we found that imagining a non-predictive gaze cue could orient attention towards the gazed-at hemifield. Such attentional effect persisted even when the imagery gaze cue was counter-predictive of the target hemifield, and could be generalized to biological motion cue. Besides, this effect could not be simply attributed to low-level motion signal embedded in gaze cues. More importantly, an eye-tracking experiment carefully monitoring potential eye movements demonstrated the imagery-induced attentional orienting effect induced by social cues, but not by non-social cues (i.e., arrows), suggesting that such effect is specialized to visual imagery of social cues. These findings accentuate the demarcation between social and non-social attentional orienting, and may take a preliminary step in conceptualizing voluntary visual imagery as a form of internally directed attention.

Visual mental imagery of atypical color objects attracts attention to an imagery-matching object

Mental imagery attracts attention to imagery-matching stimuli. However, it remains unknown whether voluntarily imagined atypical color also attracts attention to a stimulus that matches the imagery when the imagined stimuli are color-diagnostic objects, which are strongly associated with typical color. This study investigated whether people can voluntarily imagine atypical colors of such objects and attend to imagery-matching stimuli. Participants in the imagery group were instructed to imagine an atypical color of the black-white objects according to the instructed color or voluntarily selected color, whereas participants in the control group were instructed to attend to the objects without any instruction of imagery. Thereafter, they detected a color target in a visual search task. Results revealed that participants in the imagery group directed attention to the imagery-matching atypical color, not to the original color of the object in the search. Meanwhile, participants in the control group did not demonstrate any attentional guidance. These results suggest that voluntarily imagining atypical color can attenuate mental representations of the original color imagery and change attention to a stimulus that matches imagery.

Imagined object files: Visual imagery produces partial repetition costs where perception does not

The present study explored whether object (or event) files can be formed that integrate color imagery and perceptual location features. To assess this issue, a cue-target procedure was used whereby color imagery was cued to be generated at a particular location in space, which was then followed by a perceptual color discrimination task. Partial repetition costs (PRCs) were then measured by varying the overlap of the color and location features of the cue and target to evaluate whether an object/event file was formed. Robust PRCs were observed when imagery was generated at a location, supporting the idea that imagery and perception can be incorporated into a common event file. It was also revealed that the PRC effects for perceptual color cues were tenuous-they did not reach significance in the present study. Overall, the present study indicates that imagery can produce stronger binding effects than perception, offering important insights into the role that active engagement plays in the formation of object/event files.

A comparison of mental imagery and perceptual cueing across domains of attention

Mental imagery and perceptual cues can influence subsequent visual search performance, but examination of this influence has been limited to low-level features like colors and shapes. The present study investigated how the two types of cues influence low-level visual search, visual search with realistic objects, and executive attention. On each trial, participants were either presented with a colored square or tasked with using mental imagery to generate a colored square that could match the target (valid trial) or distractor (invalid trial) in the search array that followed (Experiments 1 and 3). In a separate experiment, the colored square displayed or generated was replaced with a realistic object in a specific category that could appear as a target or distractor in the search array (Experiment 2). Although the displayed object was in the same category as an item in the search display, they were never a perfect match (e.g., jam drop cookie instead of chocolate chip). Our findings revealed that the facilitation of performance on valid trials compared with invalid trials was greater for perceptual cues than imagery cues for low-level features (Experiment 1), whereas the influence of these two types of cues was comparable in the context of realistic objects (Experiment 2) The influence of mental imagery appears not to extend to the resolution of conflict generated by color-word Stroop stimuli (Experiment 3). The present findings extend our understanding of how mental imagery influences the allocation of attention.

Top-down then automatic: Instructions can continue to influence visual search when no longer actively implemented

The present study investigated the automaticity of top-down instructions in visual search when the instruction was no longer actively implemented. To do so, we exploited the Priming of Pop-out (PoP) effect, a selection history phenomenon that reflects faster responses when the target and distractor colors are repeated than switched across trials of singleton search. We then had participants perform a color singleton search task where they implemented the instruction of imagining the opposite color of the previous target, which put the target colors underlying PoP and the imagery instruction in opposition. To assess automaticity, on some trials participants were instructed to stop implementing the imagery instruction. When the imagery instruction was implemented, responses were faster when the target and distractor colors switched (i.e., imagery congruent) than repeated (i.e., imagery incongruent) across search displays - a pattern of results opposite to the PoP effect. When participants were to not implement this instruction, the PoP effect was absent, indicating the imagery instruction had a lingering influence on visual search. This remained true even when participants reported successfully not implementing the instruction, and only when the imagery abandonment instruction was supplanted by a different top-down task was the lingering influence removed such that the PoP effect returned. Overall, the present study demonstrates that top-down instructions can continue to influence visual search despite the will of the observer.

It hurts more than it helps: Cuing T1 with imagery can impair T2 identification in an attentional blink task

The purpose of the present study was to evaluate whether cuing a first target with color imagery could influence second target identification using the two-target attentional blink procedure of MacLellan, Shore, and Milliken (2015, Psychological Research, 79, 556-569.). This method asks participants to identify a first target word interleaved with a distractor word and a second target word that follows the first target after a variable stimulus onset asynchrony. Prior to each trial of the two-target procedure, participants were cued to generate color imagery that was congruent with the color of the first target word, the color of the distractor word, the color of neither the first target or distractor words (Experiment 2), or to withhold generating color imagery (Experiment 3). The results revealed that identification of the second target was impaired when the cue was congruent with the distractor word, and equivalent when the cue was congruent with the first target word, relative to when color imagery was withheld. These results suggest that the attentional resources needed to identify the first target were not reduced by a match between the color of imagery and the first target, but a match between the color of imagery and the distractor increased the attentional resources needed to identify the first target.

Comparing imagery and perception: Using eye movements to dissociate mechanisms in search

It has been demonstrated that color imagery can have a profound impact when generated prior to search, while at the same time, perceptual cues have a somewhat limited influence. Given this discrepancy, the present study evaluated the processes impacted by imagery and perception using a singleton search task where participants had to find an oddball colored target among homogenously colored distractors. Prior to each trial, a perceptual color was displayed or imagery was generated that could match the target, distractors, or neither item in the search array. It was revealed that color imagery led to both a larger benefit when it matched the target and a larger cost when it matched the distractors relative to perceptual cues. By parsing response times into pre-search, search, and response phases based on eye movements, it was revealed that, while imagery and perceptual cues both influenced the search phase, imagery had a significantly greater influence than perceptual cues. Further, imagery influenced pre-search and response phases as well. Overall, the present findings reveal that the influence of imagery is profound as it affects multiple processes in the vision-perception pipeline, while perception only appeared to impact search.

Looking into the mind's eye: Directed and evaluated imagery vividness modulates imagery-perception congruency effects

While most people have had the experience of seeing a representation in the mind's eye, it is an open question whether we have control over the vividness of these representations. The present study explored this issue by using an imagery-perception interface whereby color imagery was used to prime congruent color targets in visual search. In Experiments 1a and 1b, participants were required to report the vividness of an imagined representation after generating it, and in Experiment 2, participants were directed to create an imagined representation with particular vividness prior to generating it. The analyses revealed that the magnitude of the imagery congruency effect increased with both reported and directed vividness. The findings here strongly support the notion that participants have metacognitive awareness of the mind's eye and willful control over the vividness of its representations.