Stimulus-driven attentional capture by subliminal onset cues

Atten Percept Psychophys (2015) 77:737–748 DOI 10.3758/s13414-014-0802-4 Stimulus-driven attentional capture by subliminal onset cues Tobias Schoeberl & Isabella Fuchs & Jan Theeuwes & Ulrich Ansorge Published online: 18 December 2014 # The Psychonomic Society, Inc. 2014 Abstract In two experiments, we tested whether subliminal abrupt onset cues capture attention in a stimulus-driven way. An onset cue was presented 16 ms prior to the stimulus display that consisted of clearly visible color targets. The onset cue was presented either at the same side as the target (the valid cue condition) or on the opposite side of the target (the invalid cue condition). Because the onset cue was presented 16 ms before other placeholders were presented, the cue was subliminal to the participant. To ensure that this subliminal cue captured attention in a stimulus-driven way, the cue’s features did not match the top-down attentional control settings of the participants: (1) The color of the cue was always different than the color of the non-singleton targets ensuring that a top-down set for a specific color or for a singleton would not match the cue, and (2) colored targets and distractors had the same objective luminance (measured by the colorimeter) and subjective lightness (measured by flicker photometry), preventing a match between the top-down set for target and cue contrast. Even though a match between the cues and topdown settings was prevented, in both experiments, the cues captured attention, with faster response times in valid than invalid cue conditions (Experiments 1 and 2) and faster response times in valid than the neutral conditions (Experiment 2). The results support the conclusion that subliminal cues capture attention in a stimulus-driven way. Keywords Subliminal perception . Cueing . Attention capture T. Schoeberl (*) : I. Fuchs : U. Ansorge Department of Psychology, University of Vienna, Vienna, Austria e-mail: J. Theeuwes Department of Psychology, Vrije Universiteit Amsterdam, Amsterdam, Netherlands Evolution has equipped the human visual system with functional mechanisms of attentional guidance to cope with threats imposed on the organism in the course of its phylogeny. Selective attention is the gateway to cognition, allowing us to allocate mental resources to visual input relevant for the task at hand. One very functional attentional guidance mechanism could ensure the failsafe selection of abrupt onsets in the visual periphery. As abrupt onsets in the periphery may contain novel information and possibly a potential threat, shifting attention to the location of an abrupt onset may provide an important survival mechanism (Breitmeyer & Ganz, 1976; Yantis & Jonides, 1984). Because from an ecological viewpoint such a mechanism should operate regardless of the current attentional set, it may not be surprising that abrupt onsets capture attention in an exogenous or stimulusdriven way. The hypothesis that abrupt onsets capture attention in a stimulus-driven way, regardless of top-down control, was initially supported (Jonides, 1981, Posner & Cohen, 1984) where participants searched for a target presented at one of several peripheral locations. If the target happened to be preceded by an abrupt onset cue (the valid cue condition), participants were relatively fast to respond to the target. However, in the invalid cue condition, when the cue was presented at a location other than the target participants were relatively slow (Jonides, 1981, Posner & Cohen, 1984). This validity or cueing effect was assumed to reflect the stimulusdriven capture of attention by the onset cue, which in turn facilitated responding to a target presented at that location relative to a condition in which the target appeared at an uncued location (Posner, 1980). These authors concluded that the validity effect reflected stimulus-driven attentional capture, because the peripheral cues were uninformative about the likely position of the target. Moreover, in Jonides (1981) a validity effect was even found if the participants were asked to actively ignore the cues. On the basis of these latter findings, it was concluded that the cueing effect must be stimulus-driven 738 as participants were not even able to overcome attentional capture when they actively tried. However, following these initial studies a whole host of new findings questioned the generalizability of the stimulusdriven nature of attentional capture by onsets. Indeed, Folk, Remington, and Johnston (1992) demonstrated that an abrupt onset cue only captured attention if participants searched for an abrupt onset target. If participants searched for a particular color defined target, there was no cueing effect of the abrupt onset cue. This finding led Folk et al. to their top-down contingent-capture theory according to which attentional capture is always contingent on a match between the top-down attentional control settings and the features of the impinging stimuli. Even though the debate of whether clearly visible (i.e., supraliminal) onset cues capture attention in a stimulusdriven way is still unresolved (see Theeuwes, 2010), more recent work has made the claim that onset cues that are presented subliminally should at least be considered to be stimulus-driven as the observer is not aware that such a cue was presented in the first place (McCormick, 1997; Mulckhuyse, Talsma, & Theeuwes, 2007). A stimulus is considered to be subliminal when the observer is not aware of this stimulus. For example, in Mulckhuyse et al. (2007) one black disk was presented as a single abrupt onset cue in the periphery, either to the right or to the left of the center of a computer screen. Immediately after this cue [with a stimulus onset asynchrony (SOA) of 16 ms], two other black disks were shown as placeholders: one in the center of the screen and one on the opposite side of the cue. In this situation, participants remained unaware that one of the onset cues was presented earlier in time than the other two placeholders as the temporal interval between cue and placeholders was too small to notice this. Even though participants were unaware that the cue had a lead time, it nevertheless captured attention, because participants were faster when a subsequent target was presented at the location of the cue (i.e., valid cue condition) than when it was presented at the location away from the cue (i.e., invalid cue condition). Although it is difficult to ensure absolute subliminality in this kind of experimental protocol (Fuchs & Ansorge, 2012a, 2012b; Fuchs, Theeuwes, & Ansorge, 2013), several findings suggested that the cues were indeed not consciously noticed by the participants, as long as the participants were not directly informed about the presence of the cues. For example, participants were not able to strategically use the subliminal cues while they were able to do so when the cues were presented supraliminally. Also, participants were not aware of the (...truncated)