Edited by: Wilfried Kunde, Julius-Maximilians-Universitaet Wuerzurg, Germany
Reviewed by: Marc Grosjean, Leibniz Research Centre for Working Environment and Human Factors, Germany; Birgit Elsner, University of Potsdam, Germany
*Correspondence: Stephan Verschoor, Cognitive Psychology Unit, Department of Psychology, Leiden University, Wassenaarseweg 52, 2333 AK Leiden, Netherlands. e-mail:
This article was submitted to Frontiers in Cognition, a specialty of Frontiers in Psychology.
This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.
One of the great questions in psychology concerns how we develop to become intentional agents. Ideomotor theory suggests that intentional actions depend on, and emerge from the automatic acquisition of bidirectional action–effect associations: perceiving an action–effect sequence creates an integrated representation that can be employed for action control in the opposite order, selecting an action by anticipating its effect. We provide first evidence for the spontaneous acquisition of bidirectional action–effect associations in 9- 12-, and 18-month-olds, suggesting that the mechanism underlying action–effect integration is in place at the latest around 9 months of age.
Humans actively manipulate their environment to reach goals, that is, to produce particular intended effects. As the selection of goal-directed actions logically depends on associations between actions and their consequences, memories for actions and their consequences must exist to permit the actor to choose the right action for a given desired outcome. Some authors have suggested that intentional action and the capability to create goal representations are with us from birth on – or even earlier (e.g., Meltzoff and Moore,
One of the first theories addressing how infants (and older learners of novel actions) acquire action–effect associations and how they utilize these associations to produce goal-directed actions was put forward by James (
Evidence for the acquisition of bidirectional associations between actions and their effects has been found in different species, such as cats, rats, and pigeons, in humans ranging in age from 4-year-olds (Eenshuistra et al.,
Given this apparently high degree of automaticity and the strong evidence that very young infants are sensitive to action–effect contingencies (e.g., DeCasper and Fifer,
The present study sought for more direct evidence for the acquisition of bidirectional action–effect in infancy. Although we hypothesize that the ability to learn action–effect associations is present from early infancy, action production and action control are extremely limited in very young babies, thus rendering behavioral measurements difficult. Since investigating bidirectional action–effect acquisition requires participants to carry out some sort of motor actions, a possible lack of evidence in very young infants could simply be due to limitations in their motor capabilities rather than to the inability to associate and rely on action–effect relations. Adult and children studies on learning action–effect associations typically used manual actions such as pressing a button. Good control over these types of manual actions develops in the second half of the first year (Belsky and Most,
Our task was modeled after the experimental setup used in the free-choice experiments of Elsner and Hommel (
When adopting this paradigm for our infant subjects, we realized after piloting that versions of the original binary-choice task were too demanding. We therefore simplified the task in such a way that only one (very large) touch-sensitive key was presented to the infants, the two action alternatives being the touching or not touching of the key. Moreover, given Dutzi and Hommel's (
Three groups of infants were tested: twenty-two 9-month-olds (mean: 9.09 months, SD = 0.18, 7 female), twenty-one 12-month-olds (mean: 12.10 months, SD = 0.26, 10 female), and twenty-two 18-month-olds (mean: 18.02 months, SD = 0.32, 8 female). Four additional 9-month-olds, three 12-month-olds, and two 18-month-olds were excluded due to fussiness. One 12-month-old was excluded due to experimental error. The participants were recruited through advertizements in local papers, daycares, maternity wards, and general practitioners. Infants were randomly and equally distributed across conditions, and they received small gifts as reward. An informed consent was obtained from all caretakers.
During the experiment infants sat in their caretaker's lap in a curtained booth. The multimodal stimuli (sounds and images) were presented via a 30-inch widescreen monitor with built-in speakers situated at a distance of 60 cm from the infants. A brightly-colored touch-sensitive key was placed right in front of the infant. The key was built into a wooden board that was attached to the booth below the monitor (see Figure
Instructions were given to the caretakers prior to the experiment. The experiment consisted of two phases: the acquisition phase and the test phase. The acquisition phase was composed of two blocks of five trials with self-produced multimodal events and two blocks of five trials with action-independent multimodal events, in an alternating order. This setup resulted for all infants in 20 acquisition trials, 10 self-produced effect trials, and 10 action-independent effect presentations. We chose multimodal events to maximize their discriminability and attention-grabbing potential.
In blocks with action-independent events, infants were presented with one of the two audiovisual events five times in a row, while the caregiver prevented the infant from touching the key by gently holding the infant's hands. To ensure the infant paid attention to the screen the presentation was triggered by the experimenter, who monitored the infant online. In case of distraction the experimenter waited for attention to return. In blocks with self-produced events, the infant's hands were free and could press the touch-sensitive key. Each touch of the key immediately elicited a presentation of an audiovisual event. Before another effect could be elicited the previous effect had to end. The caretakers were instructed to encourage the infants to press the key. Between the blocks there was a short break of 10 s to ensure that infant and caretaker were ready for the next block. Additionally, a red or green dot was presented on the monitor during the blocks to remind the caretakers which block they were in. The bimodal effects were two distinct 500 ms long meaningless sounds that started simultaneously with the 1000 ms presentations of a picture (either bright-colored cartoon of a car or a mouse)
After the acquisition phase there was a 30 s break during which caretaker and infant turned away from the monitor while engaging in entertaining the infant. The test phase consisted of three trials, in which the previously self-produced event, the previously experienced action-independent event, or no event was presented. Each of these trials lasted 30 s, during which the infant could freely touch the key. In between the test trials there was a 10 s break during which the caretaker prevented the infant from responding by holding his/her hands. The self-produced and action-independent events were presented first and second, or vice versa, with the order being balanced across participants, while the baseline trial was always administered last – so to minimize possible forgetting and extinction of action–effect associations. Methods were approved by the ethical committee of the Leiden University, Institute for Psychological Research.
In acquisition trials, we measured latencies online and, based on the offline inspection of the video tape, the number of undetected motor responses (visible scratches and touches of the key that were too light for the conductance-sensitive key to detect) and the number of responses on which the infants were helped by the caretaker. Given that the acquisition of action–effect associations is sensitive to contingency and extinction (Elsner and Hommel,
Test-trial type | Self-produced | Action independent | No event | |||
---|---|---|---|---|---|---|
Age groups | # | % | # | % | # | % |
9-month-olds | 5.00 | 38.95 | 4.91 | 41.23 | 2.50 | 19.73 |
12-month-olds | 3.67 | 36.38 | 4.33 | 41.60 | 2.24 | 22.02 |
18-month-olds | 4.86 | 49.53 | 4.36 | 26.67 | 2.41 | 23.75 |
One-way between-subjects ANOVAs were carried out to assess possible differences between the three age groups in the acquisition phase. No reliable differences were obtained for the mean latencies for responses in trials with self-produced events, in the percentage of responses in which the infants were helped by the caretaker, or in the timing of the presentation of the action-independent events (
To assess possible differences in motivation and/or motor abilities, we ran an ANOVA on the total number of responses made in all three test trials, but no effect of age was obtained. The mean number of responses during the test phase was 11.45.
A between-subjects ANCOVA was carried out on the latencies of first responses in the test trials, with trial type (previously self-produced vs. action-independent stimulus event) as within-subjects and age group (9, 12, 18 months) as between-subjects factor (see Figure
We ran another mixed-factor ANCOVA on the response proportions in the test trials, normalized through an Arcsin transformation. Trial type and age group served as factors (see Figure
In the present study we sought evidence for the spontaneous acquisition of bidirectional action–effect associations in early infancy. As expected, 9-, 12-, and 18-month-olds were faster to respond to events that they previously had actively produced than to action-independent events, indicating that all age groups indeed formed bidirectional action–effect associations during the acquisition phase. Moreover, at least the 18-months-olds also had a stronger tendency to perform the action again and more often compared when presented with the effect they previously caused than with the action-independent event. Altogether, we consider this pattern a rather close replication of the Elsner and Hommel (
Unexpectedly, the latency measure turned out to be more sensitive than the response-frequency measure, which showed evidence for action–effect acquisition in the 18-month-olds only. This differential sensitivity might be due to several, not necessarily mutually exclusive factors. For one, it is possible that the younger infants were creating weaker or less specific associations between action and effect representations in the acquisition phase. These weaker associations might have been sufficient to drive the first response, which therefore was faster to self-produced effects, but might have fallen prey to extinction too soon to produce a larger number of responses to self-produced effects than to action-independent effects. Indeed, some evidence for extinction has been obtained even in adults (Elsner and Hommel,
A disadvantage of our simplified design is that it does not allow distinguishing associations between the effect stimuli and specific motor responses from associations between effect stimuli and a broader range of motor activities. For instance, it is possible that the self-produced effect became associated not so much with particular manual key-reaching actions but with general motor activity or playing in general, while the action-independent effect became associated with lack of activity. On the one hand, such an approach does not seem to fit with the behavior of our participants in the action-independent effect condition – as evident from the session tapes, which did produce motor activity that however was not specifically directed to the key. On the other hand, even such a rather unspecific association between effect stimuli and motor activation as such must rely on bidirectional associations between action codes and action–effects codes, as predicted from ideomotor theory.
In summary, our findings demonstrate the spontaneous, non-intentional acquisition of bidirectional action–effect associations in infants no older than 9 months. This observation by no means contradicts nativist ideas about action goal representations but it does provide a theoretical alternative that makes the less parsimonious nativist assumptions unnecessary. Apparently, infants are able to pick up action effects that they are able to control on the fly and establish bidirectional associations between representations of these action effects and the motor actions (or class of motor action) producing them. This way, infants acquire not only possible future action goals but also the means to reach them whenever they might become interested in doing so later on. In other words, human action goals might be grounded in and through the acquisition and anticipation of action-contingent perceptual effects. This fits with findings from studies on action perception, showing that infants around 9 months more readily encode actions that have salient action effects as goal-directed (Biro, Verschoor, Coalter and Leslie, in preparation; Biro and Leslie,
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
This research was supported by the Netherlands Organization for Scientific Research. We especially thank Thijs Schrama for technical support and Birgit Elsner for theoretical and methodological assistance.
1We decided not to balance action-independent and self-produced effects across participants after a pilot experiment had revealed no preference for one or the other effect. The pilot investigated 15 participants, five from each of the three age groups. Infants were shown the button but prevented from touching; and it was checked whether the infant was actually looking at the button. We then presented the two bimodal events in random order, and the infant had the opportunity to touch the button for 30 s. A short break, during which infants were prevented from reacting again, divided the two presentations. The two effect stimuli did not yield any reliable difference in the latencies [