Academic journal article Attention, Perception and Psychophysics

Feature-Based Attention to Unconscious Shapes and Colors

Academic journal article Attention, Perception and Psychophysics

Feature-Based Attention to Unconscious Shapes and Colors

Article excerpt

Two experiments employed feature-based attention to modulate the impact of completely masked primes on subsequent pointing responses. Participants processed a color cue to select a pair of possible pointing targets out of multiple targets on the basis of their color, and then pointed to the one of those two targets with a prespecified shape. All target pairs were preceded by prime pairs triggering either the correct or the opposite response. The time interval between cue and primes was varied to modulate the time course of feature-based attentional selection. In a second experiment, the roles of color and shape were switched. Pointing trajectories showed large priming effects that were amplified by feature-based attention, indicating that attention modulated the earliest phases of motor output. Priming effects as well as their attentional modulation occurred even though participants remained unable to identify the primes, indicating distinct processes underlying visual awareness, attention, and response control.

Early theories of visual attention and visual awareness hypothesized a close connection between both processes: Only objects we attend to should reach awareness (James, 1890; cf. Merikle & Joordens, 1997; O'Regan & Noë, 2001; Posner, 1994). However, recent studies suggest that visual attention and awareness are distinguishable and depend on different neurophysiological processes (Dehaene, Changeux, Naccache, Sackur, & Sergent, 2006; Koch & Tsuchiya, 2007; Lamme, 2003, 2005). In particular, several studies have shown effects of space-based attention on stimuli that do not reach visual awareness (e.g., Kentridge, Nijboer, & Heywood, 2008; Melcher, Papathomas, & Vidnyánszky, 2005; Sumner, Tsai, Yu, & Nachev, 2006; Zhaoping, 2008). Recently, Shin, Stolte, and Chong (2009) demonstrated attentional effects on contrast thresholds for the detection of grating stimuli and on thresholds for the discrimination of gender in faces, for stimuli rendered invisible by binocular rivalry.

A further development in visual attention research is the growing interest in attentional processes based on visual features (such as color, shape, or motion direction) instead of spatial position. It has been shown that when macaque monkeys attend to the direction of a moving texture, feature-based attention modulates throughout the visual field the responses of neurons selective for that motion direction (Treue & Martínez-Trujillo, 1999). Effects of feature-based attention have also been demonstrated in numerous other psychophysical, imaging, and single-unit studies using motion as well as color or shape stimuli (e.g., Corbetta, Miezin, Dobmeyer, Shulman, & Petersen, 1990; Martínez-Trujillo & Treue, 2004; Mounts & Melara, 1999; O'Craven, Rosen, Kwong, Treisman, & Savoy, 1997; Sàenz, Buracas, & Boynton, 2002, 2003; Serences & Boynton, 2007; Tapia, Breitmeyer, & Shooner, 2010; for a review, see Maunsell & Treue, 2006).

But can feature-based attention also be dissociated from visual awareness? Kanai, Tsuchiya, and Verstraten (2006) employed continuous flash suppression where an adaptation stimulus is rendered invisible by presenting rapidly changing masking patterns to the other eye. They demonstrated that the invisible adaptation stimulus (a bar slightly tilted from the vertical axis) was still able to induce a tilt aftereffect (the perception of opposite tilt in a subsequently presented, truly vertical stimulus). Adaptation to invisible stimuli was modulated by feature-based attention, with stimulus orientation as the relevant feature. Note, however, that tilt adaptation is a slow-acting process, working in a time range of seconds or minutes. What is still lacking is a paradigm able to trace the time course of feature-based attention in ongoing, speeded visuomotor processing.

In the domain of space-based attention, such a paradigm was devised by Schmidt and Seydell (2008). …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.