Children's time estimation literature lacks of studies comparing prospective and retrospective time estimates of long lasting ecological tasks, i.e. tasks reflecting children's daily activities. In the present study, children were asked to estimate prospectively or retrospectively how much time they played a video game or read a magazine. Regardless of the task, the results revealed that prospective time estimates were longer than the retrospective ones. Also, time estimates of the video game task were longer, less accurate and more variable than those of the reading task. The results are discussed in the light of the current literature about time estimation of long lasting ecological tasks.

Introduction

From an adaptive stand point, time estimation is an important ability that individuals need to master in order to adapt to their environment. On that regard, literature on time estimation draws a distinction between prospective and retrospective timing [1], [2], [3], [4], [5]. In the former case, participants are informed in advance that they will have to judge time, while, in the latter case, they are told they will have to do so only after they have completed a task. In both situations, time judgments are made after the task is over. However, while they execute the task, participants of the prospective condition are aware that a time judgment will be required, while participants from the retrospective group are uninformed of this additional request. Since time estimation is made at the same moment, i.e. once the task is over, the key difference between these two conditions is that in the prospective paradigm, participants are aware that time is a critical component during the task, and therefore, can allow more attentional resources to time [6]. Thus, whereas prospective timing is reported to depend mainly on the amount of attention dedicated to time —with more attention to time resulting in longer perceived duration— retrospective timing is based mostly on memory processes and the number along with complexity of events that occur during the period to be timed, with more events and higher complexity resulting in longer perceived duration [3], [7]. Generally speaking, prospective time estimates are reported to be longer and less variable than retrospective time estimates [3]. Although researchers have been interested in understanding the paradigm differences with adult participants, very few have studied them with children samples.

Literature on children's prospective time estimation indicates that they become more sensitive to time between 3- and 8-years old [8], [9], [10]. Indeed, some authors report that children are less sensitive at 3- than at 5-years old, and that both groups are less sensitive than children at 8 [11], [12]. Moreover, some authors have reported that 8-year old children are prone to the same temporal illusions or effects than adults are: empty intervals are overproduced compared to filled intervals [13] and detracting attention from time results in temporal underestimation [10], [14]. Even if these findings are relevant for a better understanding of the developmental trajectory for time estimation by humans, some limitations could be addressed to this portion of the timing and time perception literature. First of all, there is a lack of studies comparing directly both time estimation paradigms (i.e. prospective vs. retrospective) with children samples. Secondly, there is a lack of studies addressing the capabilities of children for estimating long intervals (i.e. in the range of minutes), intervals marked by a task having some ecological validity. These two issues will be further discussed below.

As underlined by many authors, there is a need in the time estimation literature for studies where prospective and retrospective paradigms would be compared within the same task [3], [15]. This observation also applies specifically to the time estimation literature emphasizing the participation of children. As a matter of fact, of all the studies involving children participants that can be found in this literature, very few have used the retrospective paradigm. Moreover, in a recent meta-analysis on the effect of the cognitive load on prospective and retrospective time estimates, none of the data which contributed to the reported effect sizes came from studies comparing both paradigms in a children sample [1]. Finally, as Block, Zakay and Hancock [16] mentioned, comparing children's, adolescent's and adult's retrospective time estimates could provide the literature with an important theoretical and practical developmental knowledge about the processes involved in time estimation. As cognitive processes implied in time estimation (e.g. attention, memory) develop as children advance in age, a first step toward developmental comparisons could be to assess both time estimation paradigms in a children sample. This approach could then provide the occasion to verify if the results replicate what is generally found in the adolescent's and adult's time estimation literatures.

Another weakness of the psychological time literature that also applies to children research concerns the nature of the tasks used in the studies. Indeed, as pointed out by Tobin et al. [15], and almost five decades ago by Orme [17], this literature does not offer much about the perception of time involving ecological tasks. Such tasks can be defined as long lasting tasks reflecting daily activities like reading or playing a video game. On the contrary, time perception researches normally use non ecological tasks (e.g. pure tones marking the onset and offset of a 500-ms empty interval) in order to enhance the control on the experimental situation.

As a matter of fact, time estimation studies are usually interested in duration ranging from 100 ms to few seconds [5]. Children time estimation literature is not an exception. Indeed, in his literature review of children's time estimation, Friedman [18] mentions that most studies involving children used short duration intervals, normally 10 seconds or less. Moreover, out of the 20 studies included in Block and Zakay's [3] meta-analytic review concerning paradigms' comparison, only three used durations over 4 minutes: from 7.75 to 13.9 minutes [19], from 7.7 to 19.6 minutes [20] and 60 minutes [21]. Since this 1997 meta-analysis, only two studies concerned with a direct comparison of both paradigms and long durations were published: 8 or 24 minutes [22] and 12, 35 or 58 minutes [15]. Furthermore, of all studies that used durations above four minutes, only Tobin and Grondin [22] used a non-adult sample (participants were 14 or 15 years old).

Besides the duration issue, the nature of the task used in children's time estimation literature can be judged as quite different from what children are asked to do on a daily basis. For instance, the filled-duration effect was tested with children. This effect reveals that filled intervals are generally perceived as longer than empty intervals of the same length. To explore the filled-duration effect with children, researchers normally use a variety of stimuli to fill the temporal intervals: tones [11], [13], [23], [24], geometrical form pictures [10], [23]–[27], drawings [10], [24] and light bulbs [14]. Yet, in daily activities, children are asked to estimate durations of more complicated stimuli (e.g. book reading or video game play periods) than those used in the previously cited studies about the filled-duration effect.

In brief, these critics highlight the need to compare both time estimation paradigms with more ecological tasks, i.e. daily activities lasting more than 10 seconds. Indeed, tasks that are used in most experiments do not reflect the temporal demands of day to day tasks in children's life. Thus, the conclusions drawn from “non-ecological” tasks may not apply to other daily situations in which time perception is involved. With that in mind, the present study was designed to fill this gap in the literature.

The main objective of this study is to compare children's prospective and retrospective time estimates when they execute an ecological task: playing a video game. The reason behind the choice of children as participants is related to the fact that no study has ever compared prospective and retrospective time estimates with this population. Moreover, video gaming as an ecological task is a relevant choice when one considers that video gaming is a normal activity in most of children's daily life. Indeed, it takes up a large amount of children and adolescents' leisure time: up to 16 hours a week for boys and up to 9 for girls [28]. Therefore, selecting such an activity in the context of a time estimation study would be most relevant if the purpose is to estimate children's timing capabilities in a real-life situation (an ecologically valid task).

As stated earlier, only one known study has used a non-adult sample to compare prospective and retrospective time estimates with an ecologically valid task, i.e., with a task different from those normally used. Indeed, Tobin and Grondin [22] tested the hypothesis that adolescents play video games for long periods of time because they underestimate their play time. Thus, they asked adolescents of 14 and 15 years old to prospectively or retrospectively estimate the duration of three consecutive tasks: play a computer video game called Tetris (8 or 24 minutes), read a text about Einstein on a computer screen (8 minutes) and finally, play the video game (8 or 24 minutes). Half the participants were asked to prospectively estimate the duration of the three tasks while the other half had to estimate them retrospectively. Contrary to what is normally reported in time estimation literature, Tobin and Grondin [22] reported no paradigm effect: prospective and retrospective time estimates were not significantly different. Moreover, results showed that time estimates from both paradigms behaved like retrospective time estimates normally do, that is being shorter than the real duration. The authors argued that the absence of a difference between prospective and retrospective time estimates might have been caused by the fact that participants in both paradigm conditions were asked to estimate the duration of three tasks at once. Consequently, this manipulation might have changed the prospective nature of time estimates. Indeed, when the prospective paradigm is used in a study, durations are normally estimated one at the time, not three at the same time after durations have been presented to the participant. Also of interest is the study of Tobin et al. [15], which used a young adults sample (mean age of participants was 22.4 years old). Indeed, the authors have compared prospective and retrospective time estimates of long duration (12, 35 and 42 minutes) video game play periods in a computer video game center. In brief, the authors reported that prospective time estimates were: (a) longer, (b) not more or less accurate and (c) not more or less variable compared to retrospective time estimates. Therefore, we predict that, regardless of the task, children's prospective time estimates will be: (a) significantly longer (i.e. overestimated), (b) not significantly more or less accurate and (c) not significantly more or less variable than the retrospective ones.

Also, as gamers report loosing track of play time [29], it is important to consider the fact that time estimates of video game play periods can be different than those of other tasks. Thus, video game time estimates will be compared to those of a pleasant reading task. In their study with adolescents, Tobin and Grondin [22] reported that the duration of the video game period was more underestimated than the duration of a reading period. To explain these results, Tobin and Grondin argued that, in comparison with the reading task, the video game used required more cognitive resources (e.g. attention). Consequently, fewer resources were available during the video game condition to process temporal information, resulting in shorter time estimates. Thus, in the present study, we predict that children's time estimates of the video game task will be significantly underestimated compared to the reading task ones.