Inhibition of return is at the midpoint of simultaneous cues

When multiple cues are presented simultaneously, Klein, Christie, and Morris (Psychonomic Bulletin & Review 12:295–300, 2005) found a gradient of inhibition (of return, IOR), with the slowest simple manual detection responses occurring to targets in the direction of the center of gravity of the cues. Here, we explored the possibility of extending this finding to the saccade response modality, using methods of data analysis that allowed us to consider the relative contributions of the distance from the target to the center of gravity of the array of cues and the nearest element in the cue array. We discovered that the bulk of the IOR effect with multiple cues, in both the previous and present studies, can be explained by the distance between the target and the center of gravity of the cue array. The present results are consistent with the proposal advanced by Klein et al., (2005) suggesting that this IOR effect is due to population coding in the oculomotor pathways (e.g., the superior colliculus) driving the eye movement system toward the center of gravity of the cued array.     

Inhibition of return generated by voluntary saccades is independent of attentional momentum

Summoning attention to a peripheral location, either by a peripheral cue with the eyes fixed or when a voluntary saccade is made to it and gaze is then returned to the centre, delays detection of subsequent targets at that location compared to a location in the opposite visual field. It has been proposed that oculomotor activation generates this inhibition of return (IOR). This account presupposes that the asymmetry in detection results from inhibition at the cued location rather than facilitation at the uncued location. This has been confirmed for exogenously generated IOR. However, it has not, heretofore, been confirmed for “IOR” generated by voluntary saccades. The current study investigated whether the asymmetry in target detection, elicited either by a peripheral flash or by an eye movement generated in response to a central arrowhead, reflects facilitation at the opposite location due to the path of attentional momentum. Reaction times at the cued location were slower than reaction times at the opposite or perpendicular locations, which did not differ. Opposite facilitation due to attentional momentum requires that opposite be faster than perpendicular, which was not obtained. The results were the same whether IOR was generated by an exogenous cue or by a saccade executed endogenously to a central arrow.     

Inhibition of return

Immediately following an event at a peripheral location there is facilitation for the processing of other stimuli near that location. This is said to reflect a reflexive shift of attention towards the source of stimulation. After attention is removed from such a peripheral location, there is then delayed responding to stimuli subsequently displayed there. This inhibitory aftereffect, first described in 1984 and later labeled 'inhibition of return (IOR)', encourages orienting towards novel locations and hence might facilitate foraging and other search behaviors. Since its relatively recent discovery, IOR has been the subject of intensive investigation, from many angles and with a wide variety of approaches. After describing the seminal contribution of Posner and Cohen ('Who'), this review will discuss what causes IOR and, once initiated, what effects IOR has on subsequent processing ('What'). The time course ('When') and spatial distribution ('Where') of IOR, and what is known about IOR's neural implementation ('How') and functional significance ('Why') are also discussed.     

Inhibition of return is composed of attentional and oculomotor processes

Response time can be delayed if a target stimulus appears at a location or object that was previously cued. This inhibition of return (IOR) phenomenon has been attributed to a delay in activating attentional or motor processes to a previously cued stimulus. Two experiments required subjects to localize or identify a target stimulus. In Experiment 1, the subjects’ eyes were not monitored. In Experiment 2, the subjects’ eyes were monitored, and the subjects were instructed to either execute or withhold an eye movement to a target stimulus. The results indicated that IOR was always present for location and identification responses, supporting an attentional account of IOR. However, IOR was larger when eye movements were executed, indicating that a motor component can contribute to IOR. Finally, when eye movements were withheld, IOR was larger when a target was presented alone than when it was presented with a distractor, suggesting that IOR is larger for exogenous than for endogenous covert orienting. Together, the data indicate that IOR is composed of both an oculomotor component and an attentional component.     

Inhibition of return is not detected using illusory line motion

Inhibition of return (IOR) is the name that has been assigned to a response time (RT) delay to a stimulus presented at a recently stimulated spatial location. A commonly held explanation for the origins of IOR is that perceptual processing is inhibited and that this inhibition translates into slower RT. Three experiments with 10 subjects were used to directly test this perceptual explanation. The first two experiments assessed the level of perceptual facilitation present in the IOR paradigm using the frequency and latency of illusory line motion judgments. Contrary to the predictions of the perceptual view, the line motion and RT measures revealed only speeded processing at previously stimulated spatial locations. Experiment 3 required a simple detection response and used the same stimulus and timing parameters as those in Experiments 1 and 2. IOR was present, replicating the recent finding that judgments based on perceptual qualities of the stimulus do not demonstrate a RT delay, whereas simple detection tasks do show RT inhibition at previously stimulated locations. These findings are discussed in relation to a number of hypotheses about the origin of the RT delay.     

Inhibition of return is composed of attentional and oculomotor processes.

Response time can be delayed if a target stimulus appears at a location or object that was previously cued. This inhibition of return (IOR) phenomenon has been attributed to a delay in activating attentional or motor processes to a previously cued stimulus. Two experiments required subjects to localize or identify a target stimulus. In Experiment 1, the subjects' eyes were not monitored. In Experiment 2, the subjects' eyes were monitored, and the subjects were instructed to either execute or withhold an eye movement to a target stimulus. The results indicated that IOR was always present for location and identification responses, supporting an attentional account of IOR. However, IOR was larger when eye movements were executed, indicating that a motor component can contribute to IOR. Finally, when eye movements were withheld, IOR was larger when a target was presented alone than when it was presented with a distractor, suggesting that IOR is larger for exogenous than for endogenous covert orienting. Together, the data indicate that IOR is composed of both an oculomotor component and an attentional component.     

Inhibition of return in response to gaze cues: The roles of time course and fixation cue

Recent studies have demonstrated that orienting of attention in response to nonpredictive gaze cues arises rapidly and automatically, in a similar fashion to peripheral sudden onset cueing. However, while peripheral cues consistently elicit inhibition of return (IOR) at about 300 ms following cue onset, very little is known about inhibition effects in response to gaze cues. The present experiments systematically examined the conditions under which IOR arises with such cues. Reliable inhibition effects were obtained. Importantly, IOR emerged only at long cue-target intervals and only when a second cue actively triggered attention away from the cued location. This suggests that compared to sudden onset cueing, gaze cueing results in both prolonged facilitation and a delayed onset of inhibition processes. Thus, although both types of cues elicit very similar orienting effects in terms of their basic behavioural outcomes, there are more subtle differences between gaze and peripheral cues with respect to the maintenance and quality of those cueing effects across time.     

Auditory emotional cues enhance visual perception

Recent studies show that emotional stimuli impair performance to subsequently presented neutral stimuli. Here we show a cross-modal perceptual enhancement caused by emotional cues. Auditory cue words were followed by a visually presented neutral target word. Two-alternative forced-choice identification of the visual target was improved by emotional cues as compared to neutral cues. When the cue was presented visually we replicated the emotion-induced impairment found in other studies. Our results suggest emotional stimuli have a twofold effect on perception. They impair perception by reflexively attracting attention at the expense of competing stimuli. However, emotional stimuli also induce a nonspecific perceptual enhancement that carries over onto other stimuli when competition is reduced, for example, by presenting stimuli in different modalities.     

Audio-visual integration of emotional cues in song

We examined whether facial expressions of performers influence the emotional connotations of sung materials, and whether attention is implicated in audio-visual integration of affective cues. In Experiment 1, participants judged the emotional valence of audio-visual presentations of sung intervals. Performances were edited such that auditory and visual information conveyed congruent or incongruent affective connotations. In the single-task condition, participants judged the emotional connotation of sung intervals. In the dual-task condition, participants judged the emotional connotation of intervals while performing a secondary task. Judgements were influenced by melodic cues and facial expressions and the effects were undiminished by the secondary task. Experiment 2 involved identical conditions but participants were instructed to base judgements on auditory information alone. Again, facial expressions influenced judgements and the effect was undiminished by the secondary task. The results suggest that visual aspects of music performance are automatically and preattentively registered and integrated with auditory cues.     

Inhibition of return for faces

Inhibition of return (IOR) refers to slower reaction times when a target appears unpredictably in the same location as a preceding cue, rather than in a different location. In the present study, frontal images of human faces were presented intact as face configurations, were rearranged to produce scrambled-face configurations, or were pixilated and randomized to produce nonface configurations. In an orienting paradigm designed to elicit IOR, face and scrambled-face stimuli were used as cues (Experiment 1), as targets (Experiment 2), or along with pixilated nonface stimuli as both cues and targets (Experiment 3). The magnitude of IOR for subsequent localization targets was unaffected by cue configuration. Likewise, the magnitude of IOR was unaffected by target configuration. These results suggest that IOR is a "blind" mechanism that is unaffected by the mere occurrence of biologically relevant cue and target stimuli.     

Inhibition of return promotes stop-signal inhibition by delaying responses

Inhibition of return (10R) refers to a mechanism that slows response times (RTs) to detect, localize, or discriminate a target that is presented at a location previously occupied by an irrelevant peripheral cue. Generally, the slowing of RTs is described as a negative effect on responding that is believed to promote searching to new locations. In this report, we consider whether IOR might benefit performance when the goal is to prevent a prepared response. Using the stop-signal paradigm, we show that IOR improved the ability to inhibit a prepared response by delaying responses to the target. Thus, in addition to aiding visual search, IOR may also provide an opportunity for the adjustment of decisions and behaviour in accordance with the demands of a dynamic environment.     

Effects of spatial cues on locating emotional targets

Inhibition of return (IOR) refers to slower responding to a visual target appearing at a previously cued versus uncued location. In three experiments, we asked whether IOR would be affected by the emotional content of target stimuli. Participants reported the location of negative (spiders, angry faces) or neutral (objects, neutral faces) targets as quickly and accurately as possible after a valid or invalid location cue (a simple circle). IOR was significantly smaller when detecting negative versus neutral targets, but only after repeated exposures to these stimuli (i.e., with blocked presentations). This effect was eliminated when target type was randomized within blocks. By presenting negative versus neutral targets in short alternating blocks and examining IOR on the first trial of each new block, we show that the emotional modulation of IOR stems from the affective context in place before visual orienting is initiated, not by perceptual processing of the target after cue offset.     

Inhibition of return exaggerates change blindness

Peripheral cues trigger attention shifts, which facilitate perceptual processing and enhance visual awareness. However, this facilitation is superseded by an inhibition of return (IOR) effect, which biases attention away from the cued location. While the link between facilitatory effects of visual attention and awareness is well established, no study has reported negative effects of spatial cueing on visual awareness. This failure is puzzling, given the claim that attention is a necessary precondition for awareness. If attention is necessary for awareness, inhibiting attention should also inhibit awareness. This leads to a slightly counterintuitive prediction: Spatial cueing will inhibit awareness at long cue–target latencies. This study shows that subliminal peripheral cues exaggerate change blindness at long cue–change latencies, demonstrating that IOR can suppress visual awareness of changes and suggesting that IOR can directly affect the contents of consciousness.     

Speech segmentation is facilitated by visual cues

Evidence from infant studies indicates that language learning can be facilitated by multimodal cues. We extended this observation to adult language learning by studying the effects of simultaneous visual cues (nonassociated object images) on speech segmentation performance. Our results indicate that segmentation of new words from a continuous speech stream is facilitated by simultaneous visual input that it is presented at or near syllables that exhibit the low transitional probability indicative of word boundaries. This indicates that temporal audio-visual contiguity helps in directing attention to word boundaries at the earliest stages of language learning. Off-boundary or arrhythmic picture sequences did not affect segmentation performance, suggesting that the language learning system can effectively disregard noninformative visual information. Detection of temporal contiguity between multimodal stimuli may be useful in both infants and second-language learners not only for facilitating speech segmentation, but also for detecting word–object relationships in natural environments.     

Inhibition of return to occluded objects

Since many visual objects are vulnerable to occlusion, an active process that tracks objects behind occluders confers considerable ecological validity to the visual system. We studied this possibility by testing whether inhibition of return can be observed with occluded objects. In our experiments, two moving objects disappeared or reappeared behind occluders while a cue and a probe were presented. Contrary to the results of a previous study (Tipper, Weaver, Jerreat, & Burak, 1994), responses were consistently delayed for the cued object that was occluded when it was cued (Experiment 1), when it was probed (Experiment 2), or both (Experiment 3). These results suggest that attention can select occluded objects that are out of view. Our findings are in line with prior studies that have demonstrated similar perceptual/attentional effects for occluded objects, as well as for visible objects.     

Inhibition of return in discrimination tasks

Although inhibition of return is known to affect a wide range of detection tasks, it has not been found consistently in discrimination tasks. To examine this issue, 5 experiments were conducted in which participants discriminated between a visual target and a distractor. The responses were not inhibited if, before the onset of stimuli, attention had been overtly oriented (i.e., an eye movement was made) to the future target location and the stimulus at that location was the same symbol as the upcoming target. However, if attention was covertly oriented (i.e., no eye movement was made) to the future location of the target, or if the stimulus at the earlier attended location was a symbol different from the target, responses to the target were inhibited. Overall, the findings provide insights into the relation between movements of attention and discrimination judgments and support the notion that inhibition of return is an attentional phenomenon.     

Facial age cues and emotional expression interact asymmetrically: age cues moderate emotion categorisation

Facial attributes such as race, sex, and age can interact with emotional expressions; however, only a couple of studies have investigated the nature of the interaction between facial age cues and emotional expressions and these have produced inconsistent results. Additionally, these studies have not addressed the mechanism/s driving the influence of facial age cues on emotional expression or vice versa. In the current study, participants categorised young and older adult faces expressing happiness and anger (Experiment 1) or sadness (Experiment 2) by their age and their emotional expression. Age cues moderated categorisation of happiness vs. anger and sadness in the absence of an influence of emotional expression on age categorisation times. This asymmetrical interaction suggests that facial age cues are obligatorily processed prior to emotional expressions. Finding a categorisation advantage for happiness expressed on young faces relative to both anger and sadness which are negative in valence but different in their congruence with old age stereotypes or structural overlap with age cues suggests that the observed influence of facial age cues on emotion perception is due to the congruence between relatively positive evaluations of young faces and happy expressions.     

Inhibition of return using discrimination of location

The present study investigated "inhibition of return" which refers to increased response latency when the target in a location discrimination task appears in the same location on consecutive trials. Location discrimination tasks were performed by 28 university students (19-21 years of age) in two experiments. In Exp. 1 the task was to press a left or right button in response to a stimulus displayed on a computer screen. The first condition manipulated stimulus-response compatibility which resulted in changing the inhibition of return. Inhibition of return was stronger when the condition was stimulus-response incompatibility. This result shows that inhibition of return functions strongly under incompatible conditions. A second condition required performance of dual tasks in Exp. 2. Again, changes in inhibition of return were seen. These results show that inhibition of return functions strongly under both dual task and incompatible conditions. Inhibition of return was interpreted as functioning strongly when the task was more difficult.     

Inhibition of return and manual pointing movements

To examine whether the motor inhibition of return (IOR) postulated by Taylor and Klein (1998, 2000) generalizes to manual guided movements or is restricted to saccadic responses, the following three experiments were conducted. The first experiment combined peripheral cues (which generate IOR) with four types of manual responses made to central targets (central arrow indicating the response location). The responses were made on a touch-screen and were the equivalent of either a detection keypress, a choice keypress, a detection-guided pointing movement, or a choice-guided pointing movement. No IOR was found for any of the responses. The second experiment replicated the main result under eye fixation control. In Experiment 3, peripheral cues and peripheral targets were used, and IOR was present in all responses. Overall, these finding suggest that motor-based IOR is restricted to the oculomotor system. Implications for motor-based IOR and attention-based IOR are discussed.     

Inhibition of return impairs episodic memory access

The term inhibition of return (IOR) refers to a bias against returning attention to a location or object that has recently been attended. The effect has been shown to occur in various perceptual tasks including stimulus detection, localization, and discrimination, but also to affect higher cognitive processes like lexical access. The present experiments examined whether inhibition of return would impair the high-level processing that is required in accessing item representations in episodic memory. The results show that reaction times for recognition memory decisions are increased under IOR. Furthermore, IOR affects the accuracy of recognition memory, and this effect interacts with the ease of memory access, manipulated, for example, by encoding depth in the learning phase. These results suggest that IOR impairs attentional processing up to the highest cognitive levels, including the access of prior item encounters in episodic memory.