Extrinsic motivation underlies precise temporal production

Kentaro Yamamoto Kyushu University

Fukuoka, Japan yama-ken@kyudai.jp

Fuminori Ono The University of Tokyo

Tokyo, Japan fuminori@fennel.rcast.u-tokyo.ac.jp

Yuki Yamada, Kyoshiro Sasaki, Keiko IhayaKyushu University

Fukuoka, Japan yamadayuk@gmail.com, k-ssk@kyudai.jp,

ihaya@hes.kyushu-u.ac.jp

Katsumi Watanabe The University of Tokyo

Tokyo, Japan kw@fennel.rcast.u-tokyo.ac.jp

Abstract—The present study examined the effect of extrinsic motivation on temporal interval production. Observers were asked to produce the duration of 2.5 sec as accurately as possible, and gained or lost a certain amount of score after each trial. The amount of provided scores varied with the color of target: red or green circle was assigned to high or low scores. We found that the higher amount of expected gain and loss decreased the absolute error of temporal production. However, no effect of motivation was found on the constant error and variable error. These results suggest that extrinsic motivation improved the precision of temporal production. We propose that the striatal dopamine system may mediate motivational influences on time perception.

Keywords- time perception; motivation; cognition

I. INTRODUCTION

Motivation influences human performance. For example, prospectors can keep digging for quite a long time because they expect striking gold. In the field of behavioral science, researchers have investigated how rewards and punishments influence human behavior. Mir et al. [1] demonstrated that monetary incentive shortened reaction times in humans. It was also reported that in an incentive-force task, observers’ hand-grip force was altered depending on the amount of monetary rewards even when the observers were unaware of the rewards [2]. Similarly, a passive viewing of the imperceptible oriented stimuli improved observers’ orientation sensitivity for the stimuli only when a liquid reward was presented at the same timing [3].

In this study, we examined the effect of extrinsic motivation on temporal performance, more specifically that on a temporal production task. When an observer is provided with a reward or a punishment depending on their performance, their performance would improve because they are motivated to gain the reward or avoid the punishment. We manipulated the amount of reward (or punishment) to change their motivation. In the experiment, observers gained (or lost) the score after temporal production in each trial. The amount of score varied with the color of target: Observers

gained (or lost) a high score when the target color was green (or red), while they gained (or lost) a low score when the target color was red (or green). The score was accumulated throughout the experimental session, and the experiment concluded when the accumulated score was exceeded a given total score. We hypothesized that observers’ performance in the temporal production task would be better in high-motivation trials (i.e., trials in which the amount of gain or loss was high) than in low-motivation trials (i.e., trials in which the amount of gain or loss was low).

II. METHOD

A. Observers Twenty adults participated in this experiment. All of

them had normal or corrected-to-normal visual acuity. They were naive as to the purpose of the experiment.

B. Appratus Stimuli were presented on a 19-inch CRT monitor. The

resolution of the monitor was 1024 × 768 pixels, and the refresh rate was 100 Hz. The presentation of stimuli and collection of data were computer-controlled (Mac Pro; Apple). The observer’s head was fixed using a chin-head rest, at a viewing distance of 57 cm. The stimuli were generated by Matlab with psychtoolbox extension [4,5].

C. Stimuli The stimuli consisted of a fixation cross, target circle, a

prompt, and visual feedback. Stimulus size is provided hereafter in visual angles. The stimuli were displayed on a black background (2.04 cd/m2). The color of the fixation cross, the prompt, the visual feedback, and the target circle in a training session were white (179 cd/m2). The color of the target circle in a test session was green (CIE xycoordinates of .279/.581 and 125 cd/m2) or red (CIE xycoordinates of .606/.340 and 45.7 cd/m2), respectively. The side lengths of the fixation cross were 1.0 × 1.0 deg. The radius of the target circles was 3.05 deg. The prompt

2011 International Conference on Biometrics and Kansei Engineering

978-0-7695-4512-7/11 $26.00 © 2011 IEEE

DOI 10.1109/ICBAKE.2011.40

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2011 International Conference on Biometrics and Kansei Engineering

978-0-7695-4512-7/11 $26.00 © 2011 IEEE

DOI 10.1109/ICBAKE.2011.40

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(“space”) and the visual feedback (digits or words) subtended approximately 0.9 deg in height.

D. Procedure Observers were individually tested in a dark room. The

experiment was consisted of a training session and a test session (Fig. 1). In the training session, observers pressed the space key to start each trial. After the central fixation cross was presented for 1 sec, the white target circle appeared at the center of display. Observers were asked to press the space key when they felt that 2.5 sec had passed from the onset of the target circle. After the observers’ response, the target circle was disappeared and a visual feedback was presented at the same location as the target circle. When the produced duration was within a range of 2.5±0.1 sec, the visual feedback provided “correct”. When the produced duration was within a range of 2.5±0.1~0.5 sec, the visual feedback provided “long” or “short”, and when the produced duration exceeded those ranges, the visual feedback provided “too long” or “too short”. The visual feedback disappeared after 1 sec. Observers performed 30 trials in the training session.

A test session followed the training session. The colored target circle (green or red) appeared instead of the white circle used in the training session. Observers were asked to press "d" key (or "k" key) when they felt that 2.5 sec had passed from the onset of the green (or red) target circle: the combination of the key and the color was counterbalanced among observers. We instructed observers to press "k" key with the right hand and press "d" key with the left hand. After observers’ response, the target circle disappeared and a gained score appeared for 1 sec. When the produced duration was within a range of 2.5±0.5 sec, observers gained 10 points or 1 point. When the produced duration exceeded this range, observers lost 10 points or 1 point. The amount of the gain or loss corresponded to the color of the target

circle. The combination of the amount of the point and color of the circle was counterbalanced among observers. Following the gained score, a cumulative sum of the scores was presented for 1 sec and then the trial was finished. The test session was terminated when the observers gained 300 points or when 100 trials were finished.

III. RESULTS

Data from six observers were excluded from analysis because they could not reach a criteria score (300) in the test session. Produced durations that exceeded a range of 2.5±0.5 sec were excluded as outliers. In order to analyze the performances in the temporal production task, we calculated three indices of error (Fig. 2): absolute error (AE), constant error (CE), and variable error (VE). These errors were calculated with the following formulae:

Absolute Error = 1n

Xi −Tn=1

n

(1)

Constant Error = 1n

Xi −T( )n=1

n

(2)

Variable Error = 1n

Xi − X( )2

n=1

n

(3)

where, Xi is the ith produced duration, T is the target duration (i.e., 2.5 sec in our experiment), X is the mean produced duration. AE indicated the mean of differences between observers’ produced durations and the target duration (2.5 sec), representing the precision of temporal production. CE was the mean difference between observers’ produced durations and the target duration with direction information, representing the bias of temporal production. VE was identical to the standard deviation of observers’

(a) (b)

Figure 1. (a) Timeline of a single trial in the training session. Visual feedback was a word, which was varied between “correct”, “long”, “short”, “too long”, and “too short” depending on the produced duration. (b) Time line of a single trial in the test session. Target circle was colored either green or red. Visual feedback was a digit which was varied between “10”, “1”, “-10”, and “-1” depending on the produced duration and color of the target. Cumulative sum was presented with a target score of 300.

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produced durations, representing the variability of temporal production.

First, we confirmed that there was no significant difference between two colors in any indices [AE: t(13) = 1.66, p = .12; CE: t(13) = 0.99, p = .34; VE: t(13) = 0.56, p= .59]. Then, we analyzed the effect of motivation on temporal production performance (Figure 2). A two-tailed, paired t-test on AE revealed that AE was significantly lower in the high motivation condition than in the low motivation condition [t(13) = 2.25, p < .05] while there were no significant differences in CE and VE ([t(13) = 1.97, p = .07; t(13) = 1.55, p = .14]).

Moreover, we analyzed the effect of motivation including the factor of hand (key) by which observers’ responses were made. Half of the observers gained (or lost) 10 points when they pressed k key by right hand and gained (or lost) 1 point when they pressed d key by left hand and vice versa for the rest of the observers. A two-way mixed between-within subjects analysis of variance (ANOVA) on AE with motivation (high and low) as a within-subject factor and hand-motivation combination (right-high, left-high) as a between-subjects factor showed a significant main effect of motivation [F(1, 12) = 7.65, p < .05]. The interaction was also significant [F(1, 12) = 7.67, p < .05]. A main effect of hand-motivation combination, however, was not significant [F(1, 12) = 0.10, p = .76]. Tests of simple main effects based on the interaction revealed that AE was lower in the high motivation condition than in the low motivation condition in right-high observers [F(1, 12) = 15.32, p < .01]. On the other hand, there was no such tendency for CE and VE. A two-way mixed between-within subjects ANOVA found no significant main effects of motivation [CE: F(1, 12) = 4.05, p = .07; VE: F(1, 12) = 2.31, p = .15] or hand-motivation combination [CE: F(1, 12) = 3.21, p = .10; VE: F(1, 12) = 0.74, p = .41]. The interaction between motivation and hand-motivation combination was also not significant [CE: F(1, 12) = 1.55, p= .24; VE: F(1, 12) = 0.49, p = .50].

IV. DISCUSSION

The present study tested whether extrinsic motivation would affect observers’ performance of the temporal production task. The results showed that AE was lower in the high motivation condition than in the low motivation condition. These results suggest that extrinsic motivation may enhance the precision of temporal production. There was no main effect of motivation for CE, further suggesting that produced duration did not differ between the motivation conditions. For VE as well as CE, there was no main effect of motivation. Hence, it was unlikely that extrinsic motivation affected the variability of observers’ responses in each trial. Taken together, our findings indicate that extrinsic motivation selectively affects the precision of temporal performance.

Further analysis including the factor of hand (key) by which observers’ responses were made revealed another interesting aspect of the present results: The effect of extrinsic motivation on the precision of temporal production was observed only for observers who responded to the highly motivational stimulus by right hand and the lowly motivational stimulus by left hand. One possible explanation of this result is that temporal production was more precise when observers responded by right hand than by left hand, and thus the effect of extrinsic motivation was counteracted for the other observers. Possibly, one of the reasons why this right-hand superiority occurs was based on handedness of the observers. In fact, 13 out of 14 observers reported that they were right-handed. Helmuth and Ivry [6] showed that variability associated with response implementation (motor delay) in a repetitive tapping task was lower for the dominant (right) hand than for the non-dominant (left) hand. Their finding suggested that motor precisions for key press are different between the dominant and non-dominant hands. Increasing the number of left-

(a) (b) (c)

Figure 2. (a) Absolute error, (b) constant error, and (c) variable error in the high and low motivation conditions. Error bars denote standard errors of the means (SEM).

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handed observers would be one way to verify our hypothesis.

The results of the present study suggest that extrinsic motivation affects the precision of temporal production, whereas it is still unclear whether intrinsic motivation is also related to the precision of temporal performance. Given that some studies showed the relationship between intrinsic motivation toward non-temporal goal and subjective experience of time passing [7], it is possible that intrinsic motivation as well as extrinsic motivation influences temporal performance, possibly regarding precision. It is a bit premature to draw a conclusion on this issue due to a scarcity of evidence, and hence, we will directly test the influence of intrinsic motivation for the achievement in a temporal task on the performance of the task.

Regarding the possible mechanism of the present finding, some researchers proposed that the striatal dopamine system mediates motivational influences on movement performance (for review see [8]). Some other researchers on time perception suggested that striatal dopamine system were also involved in timing processing (for review see [9]). Given the common neural basis between the motivational and temporal processing, we speculate that the activities of the striatal dopamine system contribute to the motivational modulation of temporal performance. Further investigations are warranted for this issue in the future.

AKNOWLEDGEMENT

This work was supported by a Grant-in-Aid for JSPS Fellows (#224466 and #213959) from the Japan Society for the Promotion of Science and research grants from the Japan Science and Technology Agency.

REFERENCES

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[6] L. L. Helmuth, & R. B. Ivry, “When two hands are better than one: reduced timing variability during bimanual movements,” Journal of Experimental Psychology: Human Perception and Performance, vol. 22, pp. 278-293, 1996.

[7] R. Conti, “Time flies: investigating the connection between intrinsic motivation and the experience of time,” Journal of Personality, vol. 69, pp. 1-26, 2008.

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[9] C. V. Buhusi, and W. H. Meck, “What makes us tick? Functional and neural mechanisms of interval timing,” Nature Reviews Neuroscience, vol. 6, pp. 755-765, 2005.

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