Review
Hidden cognitive states revealed in choice reaching tasks

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Perceptual and cognitive processes have largely been inferred based on reaction times and accuracies obtained from discrete responses. However, discrete responses are unlikely to capture dynamic internal processes, occurring in parallel, and unfolding over time. Recent studies measuring continuous hand movements during target choice reaching tasks reveal the temporal evolution of hidden internal events. For instance, the direction of curved reaching trajectories reflects attention, language representations and the spatial number line, in addition to interactions between the ventral and dorsal visual streams. This elucidates the flow of earlier cognitive states into motor outputs. Thus, this line of research provides new opportunities to integrate information across different disciplines such as perception, cognition and action, which have usually been studied in isolation.

Introduction

Progress in understanding how human cognition operates owes much to the information processing approach, which has adopted the computer metaphor of distinct processing units. The theoretical assumption of discrete intermediate stages has inspired cleverly designed experiments to identify sequential stages of perception, cognition, decision-making and motor output. Reaction times and accuracies obtained from discrete responses such as button presses have been viewed as useful and effective behavioral measurements to individuate sub-components, each adding its own processing times 1, 2.

For decades, however, an alternative view of brain processing has also persisted, reappearing under various guises including connectionism and non-linear systems analysis: multiple internal states can be activated in parallel, and coexist 3, 4, 5, 6, 7. Furthermore, these unified perspectives of perception, cognition and action have emphasized a stronger role for action in perception and cognition 5, 7, 8, 9. Although conventional discrete measurements seem adequate under the assumptions of a symbolic-computational approach to cognition, they cannot fully capture dynamic interactions of internal states over time. What has been lacking in human studies on perception and cognition are easily available behavioral paradigms to measure the temporal evolution of relevant internal events.

We shed light on ongoing endeavors to capture the dynamics of multiple cognitive states unfolding over time 4, 10, 11, 12, 13, 14. There has been an attempt to take advantage of overt actions such as saccadic eye movements and manual reaching movements to read out cognitive processes. For instance, the distributions of saccadic landing positions and changes of saccadic movement trajectories have been used to examine language, attention, memory and oculomotor control 15, 16, 17. Yet, saccades, in general, are rapid and discrete, demonstrating relatively weak trajectory modulation. In contrast, reaching movements have numerous advantages as an alternative behavioral measurement (Box 1). The continuity of reaching movements enables each sample point to be modulated by the real-time progress of a wide range of internal processes 4, 18, 19.

Neurophysiological studies have demonstrated the existence of simultaneous multiple motor plans and blurred distinctions between sensory, decision-making and motor processes in the brain 20, 21, 22, 23, 24, 25, 26, 27. This provides physiological plausibility for the view that reaching movements can reflect underlying competing cognitive states. After a brief review of these neural mechanisms, we describe examples in which the direction of curved reach trajectories reveals otherwise hidden states and processes. This new approach using reaching movements demonstrates interactive parallel processes of perception, cognition and action, bridging the gap across different disciplines in which these processes have been studied independently 5, 6, 7, 9, 10, 28.

Section snippets

Perception, cognition and action: interactive parallel processes

For simplicity and convenience, theoretical models often assume separate and discrete neural substrates for perception, cognition and action. Perceptual evidence is gathered, followed by a decision process. Then the subsequent motor output is planned and executed. However, a growing number of studies have raised the question as to whether interpreting neural activity in terms of distinct perceptual, cognitive or motor processes is appropriate for bridging dynamic neural data with behavior. For

Evidence for real-time cognitive events in reach trajectories

Recent studies using target choice reaching tasks have taken advantage of the ‘leakage’ of earlier cognitive states into the final motor output. In these studies, the analyses of reaching movements demonstrate the current locus of attention, the nature of language representations, spatial representation of numbers, and high-level decision-making processes.

Spatial representation of numbers revealed by systematic trajectory shifts

The ‘numerical distance effect’, in which reaction times and error rates systematically decrease as the numerical distance between two numbers increases, suggests that numbers are represented spatially along a continuum. This evidence of spatial number representation has been observed in adults and in infants and animals [47].

However, this is an indirect inference based on the duration for completing the entire sequence of number comparison processes. Recent studies using reaching tasks further

Using reaching to identify interactions between dorsal and ventral streams

The dorsal and ventral visual streams have been identified as comprising two separate processes: an identification system in the ventral stream, and an action system in the dorsal stream 50, 51. Continuous reaching tasks have been informative in understanding how these two visual systems are dissociated. For instance, a patient with damage to the ventral portion of the visual system demonstrates normal temporal dynamics of goal-directed reach-to-grasp movements even without recognizing objects.

Conclusions

The detailed analysis of reaching movement provides not only insights into visuo-motor behavior itself but also reveals new information regarding otherwise hidden internal events. All of the aforementioned examples in choice reaching tasks indicate that action is not always the final product of perception and cognition; reach trajectories can reveal multiple competing representations in addition to intermediate products. This emphasizes a more unified conception of perception, cognition and

Acknowledgements

We thank R.M. McPeek, R. Rafal, A.Z Khan and E.M. Messer for valuable comments. J-H.S. was supported by an R.C. Atkinson Fellowship Award.

References (70)

  • G. Hesslow

    Conscious thought as simulation of behaviour and perception

    Trends Cogn. Sci.

    (2002)
  • T.N. Welsh et al.

    The effects of response priming on the planning and execution of goal-directed movements in the presence of a distracting stimulus

    Acta Psychol (Amst.)

    (2005)
  • L. Feigenson

    Core systems of number

    Trends Cogn. Sci.

    (2004)
  • M. Ishihara

    Interaction between space and number representations during motor preparation in manual aiming

    Neuropsychologia

    (2006)
  • M.A. Goodale

    Dual routes to action: contributions of the dorsal and ventral streams to adaptive behavior

    Prog. Brain Res.

    (2005)
  • V.A. Lamme

    Towards a true neural stance on consciousness

    Trends Cogn. Sci.

    (2006)
  • S. Dehaene

    Conscious, preconscious, and subliminal processing: a testable taxonomy

    Trends Cogn. Sci.

    (2006)
  • E.K. Cressman

    On-line control of pointing is modified by unseen visual shapes

    Conscious. Cogn.

    (2007)
  • B.D. McCandliss

    The visual word form area: expertise for reading in the fusiform gyrus

    Trends Cogn. Sci.

    (2003)
  • J.C. Culham et al.

    Human parietal cortex in action

    Curr. Opin. Neurobiol.

    (2006)
  • W.H. Warren

    The dynamics of perception and action

    Psychol. Rev.

    (2006)
  • M. Spivey

    The Continuity of Mind

    (2007)
  • P. Cisek

    Cortical mechanisms of action selection: the affordance competition hypothesis

    Philos. Trans. R. Soc. Lond. B Biol. Sci.

    (2007)
  • L.W. Barsalou

    Grounded cognition

    Annu. Rev. Psychol.

    (2008)
  • M.J. Spivey et al.

    Continuous dynamics in real-time cognition

    Curr. Dir. Psychol. Sci.

    (2006)
  • D.A. Balota et al.

    Mental chronometry: beyond onset latencies in the lexical decision task

    J. Exp. Psychol. Learn. Mem. Cogn.

    (1995)
  • M.G. Coles

    A psychophysiological investigation of the continuous flow model of human information processing

    J. Exp. Psychol. Hum. Percept. Perform.

    (1985)
  • M.K. Tanenhaus

    Integration of visual and linguistic information in spoken language comprehension

    Science

    (1995)
  • K. Rayner

    Eye movements in reading and information processing: 20 years of research

    Psychol. Bull.

    (1998)
  • J.S. Magnuson

    Moving hand reveals dynamics of thought

    Proc. Natl. Acad. Sci. U. S. A.

    (2005)
  • Spivey, M.J. et al. Do curved reaching movements emerge from competing perceptions? A Reply to van der Wel et al....
  • J.I. Gold et al.

    The neural basis of decision making

    Annu. Rev. Neurosci.

    (2007)
  • A. Tosoni

    Sensory-motor mechanisms in human parietal cortex underlie arbitrary visual decisions

    Nat. Neurosci.

    (2008)
  • T. Yang et al.

    Probabilistic reasoning by neurons

    Nature

    (2007)
  • A.P. Georgopoulos

    On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex

    J. Neurosci.

    (1982)
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