Bruce Milliken

On the strategic modulation of the time course of facilitation and inhibition of return.

In studies of exogenous attentional orienting, response times for targets at previously cued locations are often longer than those for targets at previously uncued locations. This effect is known widely as inhibition of return (IOR). There has been debate as to whether IOR can be observed in discrimination as well as detection tasks. The experiments reported here confirm that IOR can be observed when target discrimination is required and that the cue-target interval at which IOR is observed is often longer in discrimination than in detection tasks. The results also demonstrate that the later emergence of IOR is related to perceptual discrimination rather than to response selection differences between discrimination and detection tasks. More difficult discrimination tasks lengthen the SOA at which IOR emerges. In contrast, increasing task difficulty by adding a distractor to the location opposite the target shortens the SOA at which IOR emerges. Together, the results reveal an adaptive interaction between exogenous and endogenous attentional systems, in which the action of the orienting (exogenous) system is modulated endogenously in accord with task demands.

The context-specific proportion congruent Stroop effect: Location as a contextual cue.

The Stroop effect has been shown to depend on the relative proportion of congruent and incongruent trials. This effect is commonly attributed to experiment-wide word-reading strategies that change as a function of proportion congruent. Recently, Jacoby, Lindsay, and Hessels (2003) reported an itemspecific proportion congruent effect that cannot be due to these strategies and instead may reflect rapid, stimulus driven control over word-reading processes. However, an item-specific proportion congruent effect may also reflect learned associations between color word identities and responses. In two experiments, we demonstrate a context-specific proportion congruent effect that cannot be explained by such word—response associations. Our results suggest that processes other than learning of word—response associations can produce contextual control over Stroop interference.

Endogenous temporal orienting of attention in detection and discrimination tasks

Endogenous temporal-orienting effects were studied using a cuing paradigm in which the cue indicated the time interval during which the target was most likely to appear. Temporal-orienting effects were defined by lower reaction times (RTs) when there was a match between the temporal expectancy for a target (early or late) and the time interval during which the target actually appeared than when they mismatched. Temporal-orienting effects were found for both early and late expectancies with a detection task in Experiment 1. However, catch trials were decisive in whether temporal-orienting effects were observed in the early-expectancy condition. No temporal-orienting effects were found in the discrimination task. In Experiments 2A and 2B, temporal-orienting effects were observed in the discrimination task; however, they were larger when temporal expectancy was manipulated between blocks, rather than within blocks.

Inhibition of Return and the Attentional Set for Integrating Versus Differentiating Information

Cuing a location with an uninformative cue leads to a facilitatory effect at that location shortly afterward and later (about 300 ms) to a negative effect called inhibition of return (IOR). Until recently, it was argued that IOR occurs in detection and localization tasks, but not in discrimination tasks. However, the authors of several recent studies have demonstrated IOR effects in discrimination tasks, although at a later cue-to-target stimulus onset asynchrony (SOA). In this study, the authors examined why IOR occurs at a later SOA in discrimination tasks. In Experiments 1 and 2, different time courses of exogenous cuing effects in detection and discrimination tasks were established. In Experiment 3, the authors examined the role of an attentional set on the time course of exogenous cuing effects by manipulating the proportion of trials in which a distractor is presented in the location opposite the target. A new framework for understanding exogenous cuing effects and their dependence on endogenous attention is proposed.

Attending, ignoring, and repetition: On the relation between negative priming and inhibition of return

A series of spatial localization experiments is reported that addresses the relation betweennegative priming andinhibition of return. The results of Experiment 1 demonstrate that slowed responses to repeated location stimuli can be obscured by repetition priming effects involving stimulus dimensions other than spatial location. The results of Experiments 2, 3A, and 3B demonstrate that these repetition priming effects may occur only when participants are required to respond to the prime display. Together, these results suggest that differences between attended and ignored repetition effects in selective attention studies of spatial localization do not provide a basis for distinguishing between spatial negative priming and inhibition of return.

Independent effects of endogenous and exogenous spatial cueing: inhibition of return at endogenously attended target locations

Inhibition of return (IOR) is thought to reflect a bias against returning attention to previously attended locations. According to this view, IOR should occur only if attention is withdrawn from the target location prior to target appearance. In the present study, endogenous attention and exogenous cueing were manipulated orthogonally. IOR was observed both when a target appeared at an unexpected location, and when a target appeared at the expected location. A similar pattern of results was obtained in a reanalysis of data from a study with Neglect patients. These results suggest that IOR is independent of endogenous orienting.

The flexibility of context-specific control: Evidence for context-driven generalization of item-specific control settings

In two experiments we address an ongoing debate concerning the processes driving context-driven modulations to the Stroop effect (Crump, Gong, & Milliken, 2006). In particular, we demonstrate that context-driven processes can modulate the size of the Stroop effect for frequency-unbiased item types. We also clarify the role of item frequency in producing context-driven modulations to the Stroop effect. Taken together, our results provide unambiguous support for the claim that contextual processing can impart fast and flexible control over the operation of selective attention processes during online performance.

Context-specific learning and control: The roles of awareness, task relevance, and relative salience

The processes mediating dynamic and flexible responding to rapidly changing task-environments are not well understood. In the present research we employ a Stroop procedure to clarify the contribution of context-sensitive control processes to online performance. In prior work Stroop interference varied as a function of probe location context, with larger Stroop interference occurring for contexts associated with a high proportion of congruent items [Crump, M. J., Gong, Z., & Milliken, B. (2006). The context-specific proportion congruent stroop effect: location as a contextual cue. Psychonomic Bulletin &Review, 13, 316-321.] Here, we demonstrate that this effect does not depend on awareness of the context manipulation, but that it can depend on attention to the predictive context dimension, and on the relative salience of the target and predictive context dimensions. We discuss the implications of our results for current theories of cognitive control.

Inhibitory processes in auditory selective attention: Evidence of location-based and frequency-based inhibition of return

The possibility that there is an inhibitory component to auditory covert orienting was addressed. Each trial consisted of a cue followed by a target, and listeners were required to detect, localize, or identify the frequency of the target. At 150-msec stimulus onset asynchrony (SOA), performance was best when stimuli sounded from the same location or were of the same frequency. However, at 750-msec SOA, performance was best when stimuli differed in location or were of different frequencies. These results document the existence of both location-based and frequency-based auditory inhibition of return.

Separate Mechanisms Recruited by Exogenous and Endogenous Spatial Cues: Evidence from a Spatial Stroop Paradigm.

The present experiments tested whether endogenous and exogenous cues produce separate effects on target processing. In Experiment 1, participants discriminated whether an arrow presented left or right of fixation pointed to the left or right. For 1 group, the arrow was preceded by a peripheral noninformative cue. For the other group, the arrow was preceded by a central, symbolic, informative cue. The 2 types of cues modulated the spatial Stroop effect in opposite ways, with endogenous cues producing larger spatial Stroop effects for valid trials and exogenous cues producing smaller spatial Stroop effects for valid trials. In Experiments 2A and 2B, the influence of peripheral noninformative and peripheral informative cues on the spatial Stroop effect was directly compared. The spatial Stroop effect was smaller for valid than for invalid trials for both types of cues. These results point to a distinction between the influence of central and peripheral attentional cues on performance and are not consistent with a unitary view of endogenous and exogenous attention.