how to manipulate attention

From Scholarpedia

Curator: Dr. Naotsugu Tsuchiya, California Institute of Technology, Pasadena, CA, USA
Curator: Dr. Christof Koch, Division of Biology, Caltech, Pasadena, CA

Psychophysical tools to manipulate top-down attention

Top-down attention and consciousness are usually tightly coupled. To dissociate these two, experimental tools that manipulate either one independently in a specific manner with few side effects are called for.

There exist at least two forms of selective attention: stimulus-driven, bottom-up, saliency-mediated attention as well as task- and goal-dependent top-down attention. Previously neutral stimuli (such as text, or abstract images) can be associated with reward or punishment to acquire additional saliency. Biologically relevant stimuli may be preferred or disliked based on individual differences (e.g., snakes, spiders, and nude pictures).

A variety of techniques to manipulate these components of attention has been invented. It is not always easy to compare them, as each method interferes with attention at a different level of processing (Sperling and Dosher, 1986; VanRullen et al., 2004).

Cueing

In Posner’s cueing paradigm, popular in the study of orienting (Posner et al., 1980), a target is preceded by an informative or a non-informative cue that appears at the target location or at fixation. Attentional effects are inferred in terms of reaction time and/or accuracy of target detection. Variants of the method demonstrated that an invisible cue can direct exogenous attention to a particular spatial location (McCormick, 1997; Kentridge et al., 2004; Rajimehr, 2004; Feng et al., 2006; Jiang et al., 2006; Sumner et al., 2006), clear support for the orienting of exogenous attention without the intervention of consciousness.

Visual search

In visual search, subjects need to find a target among distractors; reaction time is related to the number of distractors. When the search slope is steep, the search process is said to be serial, and when flat, parallel. The former is usually taken as the evidence of serial processing by top-down attention. However, the steep serial search may arise due to completely bottom-up factors (VanRullen et al., 2004). This exemplifies a case where dual-tasks and visual search methods may yield inconsistent results.

Figure 1: Dual-tasks paradigm. How performance of a secondary task in the periphery (empty red circle) is affected when a centrally presented attention-demanding task is performed simultaneously is studied with the aid of the dual-tasks paradigm.

Dual-task paradigm

Figure 2: Deciding whether or not a natural scene includes an animal can be done at the same time as the central task – here a demanding letter discrimination - (single task performance (y-axis) is the same as dual-task performance (x-axis)), while discriminating a red-green disk from a green-red one can’t be done when attention is engaged at the center. Modified from (Li et al., 2002). From (Koch and Tsuchiya, 2007) with permission.

The dual-tasks paradigm (Sperling and Dosher, 1986; Braun and Sagi, 1990; Braun and Julesz, 1998) manipulates top-down, focal attention without affecting bottom-up saliency: a central, attentionally-demanding discrimination task is present at the center of gaze, while a secondary stimulus is projected somewhere into the periphery (Fig.1). Subjects carry out either the central, the peripheral, or both tasks simultaneously while the scene and its layout remain the same.

Surprisingly, seemingly complex peripheral tasks can be done equally well under either single or dual-task condition (Li et al., 2002; Reddy et al., 2004; Reddy et al., 2006) (Fig.2, left), while other, computationally simpler tasks deteriorate when performed simultaneously with the central task (Fig.3, right). The dual-task paradigm quantifies what type of stimulus attributes can be signaled and possibly consciously perceived in the near absence of spatial attention (VanRullen et al., 2004).

Independent manipulation of top-down attention and visibility

Figure 3: (Left) An example of a bistable conscious percept (Rubin vase: two silhouettes versus a vase). (Right) It would be interesting to characterize the effect of withdrawing top-down attention from Rubin’s vase illusion by embedding this bistable percept into a dual-task experiment (Paffen et al., 2006; Pastukhov and Braun, 2007). From (Koch and Tsuchiya, 2007) with permission.

Most importantly, the dual-task paradigm can be combined with a multitude of visual illusions that render stimuli invisible, allowing the independent manipulation of top-down attention and consciousness (Fig.3), although such a full factorial analysis for many popular experiments awaits future work Attention and Consciousness/Opposite Effects.

Caveat of dual-task paradigm

The inference of attentional requirements from dual-task performance demands caution. High proficiency in such tasks is only achieved after extensive training of many hours. Such an extended training phase renders the experience of the task quite different for trained subjects from what naïve subjects experience (Joseph et al., 1997; Braun, 1998).

Neurological disorders of attention & other attention-related visual illusions

Finally, there is a class of neurological conditions as well as visual illusions in normal subjects where stimuli become invisible because of impairments in the mechanisms of top-down or bottom-up attention. Hemineglect and extinction (Driver and Mattingley, 1998), attentional blink (Raymond et al., 1992; Chun and Potter, 1995), inattentional blindness (Mack and Rock, 1998), and change blindness (Simons and Rensink, 2005) are sometimes used as positive evidence for “without attention, no consciousness” (O'Regan and Noe, 2001). Although some attributes of the visual input need attentional amplification to rise to the level of consciousness, other aspects, such as the gist of the scene and its emotional content, are quite resistant to such attentional manipulations (Mack and Rock, 1998; Anderson and Phelps, 2001).

References

• Anderson AK, Phelps EA (2001) Lesions of the human amygdala impair enhanced perception of emotionally salient events. Nature 411:305-309.
• Braun J (1998) Vision and attention: the role of training. Nature 393:424-425.
• Braun J, Sagi D (1990) Vision outside the focus of attention. Percept Psychophys 48:45-58.
• Braun J, Julesz B (1998) Withdrawing attention at little or no cost: detection and discrimination tasks. Percept Psychophys 60:1-23.
• Chun MM, Potter MC (1995) A two-stage model for multiple target detection in rapid serial visual presentation. J Exp Psychol Hum Percept Perform 21:109-127.
• Driver J, Mattingley JB (1998) Parietal neglect and visual awareness. Nat Neurosci 1:17-22.
• Feng C, Jiang Y, He S (2006) Invisible images can influence saccadic eye movements. Journal of Vision 6:819-819.
• Jiang Y, Costello P, Fang F, Huang M, He S (2006) A gender- and sexual orientation-dependent spatial attentional effect of invisible images. Proc Natl Acad Sci U S A 103:17048-17052.
• Joseph JS, Chun MM, Nakayama K (1997) Attentional requirements in a 'preattentive' feature search task. Nature 387:805-807.
• Kentridge RW, Heywood CA, Weiskrantz L (2004) Spatial attention speeds discrimination without awareness in blindsight. Neuropsychologia 42:831-835.
• Koch C, Tsuchiya N (2007) Attention and consciousness: two distinct brain processes. Trends Cogn Sci 11:16-22.
• Li FF, VanRullen R, Koch C, Perona P (2002) Rapid natural scene categorization in the near absence of attention. Proc Natl Acad Sci U S A 99:9596-9601.
• Mack A, Rock I (1998) Inattentional blindness. Cambridge, Mass.: MIT Press.
• McCormick PA (1997) Orienting attention without awareness. Journal of Experimental Psychology-Human Perception and Performance 23:168-180.
• O'Regan JK, Noe A (2001) A sensorimotor account of vision and visual consciousness. Behav Brain Sci 24:939-973; discussion 973-1031.
• Paffen CL, Alais D, Verstraten FA (2006) Attention speeds binocular rivalry. Psychol Sci 17:752-756.
• Pastukhov A, Braun J (2007) Perceptual reversals need no prompting by attention. Journal of Vision.
• Posner MI, Snyder CR, Davidson BJ (1980) Attention and the detection of signals. J Exp Psychol 109:160-174.
• Rajimehr R (2004) Unconscious orientation processing. Neuron 41:663-673.
• Raymond JE, Shapiro KL, Arnell KM (1992) Temporary suppression of visual processing in an RSVP task: an attentional blink? J Exp Psychol Hum Percept Perform 18:849-860.
• Reddy L, Wilken P, Koch C (2004) Face-gender discrimination is possible in the near-absence of attention. J Vis 4:106-117.
• Reddy L, Reddy L, Koch C (2006) Face identification in the near-absence of focal attention. Vision Res 46:2336-2343.
• Simons DJ, Rensink RA (2005) Change blindness: past, present, and future. Trends Cogn Sci 9:16-20.
• Sperling G, Dosher B (1986) Strategy and optimization in human information processing. In: Handbook of Perception and Human Performance (Boff KR, Kaufman L, Thomas JP, eds), pp 1-65. New York: Wiley.
• Sumner P, Tsai PC, Yu K, Nachev P (2006) Attentional modulation of sensorimotor processes in the absence of perceptual awareness. Proc Natl Acad Sci U S A 103:10520-10525.
• VanRullen R, Reddy L, Koch C (2004) Visual search and dual tasks reveal two distinct attentional resources. J Cogn Neurosci 16:4-14.

See Also

Attention, Cueing, Visual Search, Inattentional blindness, Attentional Blink, Change blindness