Discussion Experiment 3-II

The present study on longitudinal age effects for emotion recognition within the visual domain aimed to replicate developmental effects from the cross-sectional Experiment 3-I within a sub-sample of child participants. The current study reported children’s emotion recognition abilities with a mean age of 7 years 2 months at Time 1 and were re-tested 18 months later at a mean age of 8 years 8 months. By providing longitudinal data, the current study aimed to validate findings from the cross-sectional experiment by reducing external variables and pinning down developmental effects of emotion recognition across a time span of 1.5 years. Data suggests that RTs as well as intensity ratings for the sub-sample used in Experiment 3-II were stable between Time 1 and Time 2. Results do not support either of the two hypotheses in relation to developmental changes in RTs or intensity ratings.

3.2.4.1. Age effects

Results for intensity ratings from the longitudinal study somewhat reflect the findings from the cross-sectional Experiment 3-I. Neither the cross-sectional (Experiment 3-I) nor the present longitudinal experiment reported age-related effects for intensity perception between the two age- groups. Data from the adult control sample in Experiment 3-I, however, indicates that intensity ratings increase between the age of 9 to10 and adulthood and important developmental changes may happen during teenage years. Findings from Experiment 3-I and 3-II equally support the idea that intensity perception of emotion in faces may require a higher degree of cognitive flexibility; hence, sensitivity to emotion expression may change in early adulthood which is not captured in the present study. However, the reader is to remember that the actual intensity of faces was not modified for the purpose of the current study.

For RTs data, results from the current experiment did not replicate findings from the cross- sectional Experiment 3-I. Time of data collection did not influence RTs, although there was a trend towards faster RTs at the second data collection time. A relationship between age and speed is

typically a common finding in emotion literature and has often been reported (e.g. de Sonneville et al., 2009). It is possible that the sample size for Experiment 3-II was not sufficient and including a larger sample of participants may result in a significant difference of speed over time. Another potential explanation is that the children included in the present experiment were younger (M = 8.1) than the average child in age-group II in Experiment 3-I (M = 8.96). It is possible that age-related effects for speed, which resulted in faster RTs for older versus younger children in Experiment 3-I, is not seen in the older child group at Time 2 in Experiment 3-II because the age does not match completely.

However, the interesting fact remains: children did not improve in RTs between the ages of 6.5 and 8 in a longitudinal design, suggesting that speed-related changes may happen in stages which may be longer than the included 1.5 years period.

106 In support, Mills and colleagues (2014) conducted several MRI scans in children 2 years apart and reported changes in brain structures related to emotion mechanisms such as the anterior temporal cortex at a time gap of 2 years.

3.2.4.2. External Variable (Gender of Stimulus)

For the cross-sectional Experiment 3-I, results suggested heightened intensity perception in children for angry male versus female faces. Interestingly, the same finding was reported in the longitudinal study in the present Experiment 3-II. The male superiority effect in angry faces seemed to be a robust finding and also supports previous literature such as Becker and colleagues (2007) who reported a connection between increased masculinity in a male face and perceived angriness. Becker and colleagues suggested that ‘the angry face naturally looks more masculine’ (p. 189).

Further, the present Experiment 3-II aimed to demonstrate a link between stimulus gender- related effects and emotion rating speed in younger children which may change over the period 1.5 years. Experiment 3-I reported gender stimulus effect for RTs for faces in younger but not in older children or adults. This possibly indicate that younger children relied on external factors such as gender of stimulus for making faster decisions about emotional meaning whilst older children and adults blocked out external factors and focus on the emotions displayed per se. However, findings from the current experiment led to a rejection of this hypothesis because the sub-sample from the longitudinal study actually demonstrated the opposite effect. The present smaller sub-sample did not exhibit gender stimulus effect for faces at Time 1 but on return after 1.5 years, the same children now showed gender-stimulus effects for rating speed of happy and disgusted faces with male superiority effects.

There are two possible explanations for this finding. It is quite likely that the sub-sample used in the longitudinal data collection is too small and hence does not deliver significant statistical effects. Including a larger sample and observing development over a longer period of time may give more reliable conclusions about emotion recognition across childhood. Alternatively, it is also possible that children between the aged of 6 and 8 – as included in the present longitudinal study - become indeed more sensitive to gender effects in stimuli with age. It is possible that this effect was overshadowed in the cross-sectional Experiment 3-I due to a higher degree of variability and external influences between the two child age-groups. Current results suggest that further investigation of the link between emotion recognition and external factors such as stimulus gender during development is necessary, especially with a larger sample that may include a wider range of age-groups and adult control groups.

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3.2.4.3. Limitations & Future Research

One drawback of the current longitudinal study is that the sample size was relatively small and the current study only included data from face – rather than voice - stimuli due to the study design requirements for Experiment 3-III which compared emotion recognition in child versus adult faces. For future investigations, it would be important to include a voice emotion recognition task in order to observe children’s emotion recognition developments across two independent modalities over time.

The lack of changes in intensity ratings and RTs whilst rating adult faces in the given child sample over time may be the result of children’s stable exposure to adults over a period of 1.5 years. However, when children enter primary school, they are suddenly surrounded by a large number of same- age peers. Young children between the ages of 7 to 10 make more friends than they break up with and relationships only become more stable with age (Berndt & Hoyle, 1985). Whilst adults such as parents or teachers are usually a more or less consistent and stable component in a child’s life, young children may encounter many new social situations with same-aged peers. This may include becoming a new member in a football club or attending after-school clubs which requires the ability to adhere to a social group and efficiently read emotions of same-aged peers. In order to validate the usefulness of including adult faces to be rated by children, it would be useful to investigate children’s ability to rate emotions expressed in children as well as in adults.

3.2.4.4. Conclusion

Overall, the current longitudinal data was not able to answer questions that resulted from the cross-sectional Experiment 3-I. However, it did replicate findings such as stable intensity perception in middle childhood and also suggested that important developmental changes in emotion perception in faces may happen after the age of 10. One must include a larger sample and possibly observe performance over a longer period of time in order to make a more qualified judgement regarding the development of emotion perception based on external factors such as gender of the stimuli. The following Experiment 3-III aims to investigate the contribution of including adult rather than child faces to the inability to report significant changes in emotion perception across 1.5 years.

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