Análisis global de las técnicas utilizadas.

Findings

The present study examined a psychophysiological index of affective response in children with ASD to improve understanding of positive affect and the role it plays in the key domains of impairment in ASD. According to the motivational priming hypothesis, positive affective responses are pre-conscious, physiological responses that prepare individuals to approach or avoid certain situations. By applying the theoretical framework of the

motivational priming hypothesis), the present study sought to examine whether children with ASD would exhibit greater approach motivation to images related to circumscribed interests, relative to their typically developing peers. The study further examined whether greater approach motivation to those images would be associated with positive affect and behavior in a real-world context.

The first research question focused on PAR responses to High Autism Interest, Nonsocial Neutral Interest, and Social images in children with and without ASD. Overall, psychophysiological results were suggestive of group differences in PAR responses HAI images. Specifically, the large effect size (d= .75) suggested that participants with ASD tended to exhibit larger PAR responses to HAI images than their typically developing peers, which represents a trend toward greater appetitive responding to HAI images in the ASD group. Subjective valence ratings were consistent with this trend. Ratings for the HAI images from the ASD group were significantly more positive than ratings for the HAI images from the TD group. Considering this trend in context of the motivational priming hypothesis,

affective responses to HAI images may contribute to the intense and pervasive Circumscribed Interests that characterize many individuals with ASD.

The Group x Image Category linear trend approached significance, suggesting different patterns of PAR responses among the three image categories between the ASD and the TD group. This is consistent with previous research which has demonstrated atypical modulation of affect-modulated startle responses in individuals with ASD (Dichter et al., 2010; Wilbarger et al., 2009). In light of these findings, further exploration of the potential link between positive affective responses and approach motivation to engage in CIs is warranted.

The only other study that examined PAR responses in individuals with ASD reported notably low levels of PAR modulation to three image categories (Dichter et al., 2010). The image categories in that study were positive, neutral, and negative, and the patterns of modulation exhibited by the ASD group in that study made it difficult to determine whether the atypical pattern of responses exhibited by individuals with ASD reflected a deficit in basic affective reactivity or modulation patterns that differed based on the emotional content of the stimuli. The modulation patterns and valence ratings reported in the present study suggest that this question may best be pursued by continued examination of affective responses to images that are particularly appealing to individuals with ASD.

The relatively surprising finding of a significant main effect of group on valence ratings may also be relevant in designing future research studies. The fact that participants with ASD rated all of the images as more positive, regardless of image category, may suggest that the process of viewing images on a computer screen is a more positive experience for children with ASD than it is for children without ASD. Such a finding may have

implications for the multitude of computer-based interventions being developed to promote academic and social skills among children with ASD.

In seeking to understand why the psychophysiological results did not yield the predicted effects for the NNI and Social conditions, a few points should be considered. The final sample size was reduced due to difficulties with data acquisition, participant compliance with the protocol, and excessive artifact in a substantial portion of the psychophysiology data. Participants in the present study completed a full psychophysiology protocol as part of a larger study, which required the individual application of multiple EEG electrodes and an EEG cap. Although the process is harmless it could be unpleasant to children with sensory sensitivities or low tolerance for unfamiliar experiences. These methodological factors likely contributed to the low percentage of usable psychophysiology data. Since some of the analyses were near significance, it is likely that a larger sample size may have yielded stronger effects. An additional consideration is that the valence and arousal ratings for the Social images were relatively moderate across both groups. That is, neither group identified the Social images as especially appealing or arousing, so they may not have captured the positive or appetitive qualities of social interactions. Previous research has demonstrated the importance of using images that are sufficiently arousing, especially when examining

appetitive reflexes. For example, Sandt and colleagues found that PAR response magnitudes were significantly greater when participants viewed appetitive-related stimuli (e.g., food, erotica) compared to non-appetitive pleasant stimuli (adventure) (Sandt et al., 2009). This may have also contributed to the lack of correlation between affective responses and caregiver reports of social impairment.

The second research question pursued in the present study was whether PAR

responses correlated with caregiver reports of symptom severity. Contrary to the hypotheses, there was no correlation between PAR response magnitudes to HAI images and restricted interests as reported on the RBSR-Restricted Interest scale in the ASD group. The lack of correlation may suggest that the subscale was too specific to capture the broad range of behaviors that could be associated with potentiated affective responses to HAI images. Similarly, the relation between PAR responses to Social images and levels of social

impairment were not significant in either group. Since PAR is a particularly reliable index of positive affective state, it is possible that examining its relation with symptoms characterized by deficit or aversion (e.g., social deficits or active avoidance of social situations) is not ideal.

With regard to the third research question, the present study affirmed that EMA is a feasible measure to use with this population. It is one of only three studies to date to use EMA with participants who have ASD, and the response rates in both groups (85% in the ASD group, 94% in the typically developing group) exceeded average response rates in other EMA studies (50-90%) (Hufford & Shields, 2002). Notably, response rates did not differ between the groups and response rates did not vary as a function of age or IQ. The latter finding differs from results of a recent EMA study with adolescents who had ASD, which found that participants with lower IQs were less compliant (though inclusion criteria for IQ were roughly commensurate with the present study) (Khor et al., 2014). Additionally, the EMA protocol in the present study minimized cost by utilizing participants’ own cellular phones. The fact that such impressive response rates were obtained using a cost-effective

protocol may inform how future studies leverage limited resources to incorporate EMA into their study design.

The results from the EMA portion of the present study provide a unique picture of how children with ASD spend their free time and how their “real-world” behavior correlates with a physiological index of positive affect. The finding that children with ASD were more likely to be engaged in CI activities than their typically developing peers were to be engaged in PI activities is consistent with the defining features of CIs (i.e., intense and pervasive). It was interesting, though, that there was no group difference with regard to the frequency of nonsocial behavior. Taken together, these two findings demonstrate the importance of pressing beyond the dichotomy of social versus nonsocial behavior when examining what children with ASD are motivated to spend their time doing.

The planned analyses for examining associations between PAR response magnitudes to HAI images and self-reported positive affect were complicated by drastic reductions in sample size; however, findings suggest it may be more important to examine the frequency of certain behaviors, as opposed to self-reported affect. In the TD group, for example, there seemed to be a strong association between PAR responses to Social images and the amount of time spent in social activities. In the ASD group, there appeared to be a positive

association between PAR responses to HAI images and amount of time spent engaging in CIs.

It may be that the key to understanding how positive affect relates to motivation and behavior in ASD is examining what children with ASD do (i.e., activity types and

frequencies) rather than relying on self-report of affective state. The measure used in the EMA protocol was relatively simple; however, it still required participants to cease their

current activity, reflect on their internal state, and rate their affective state. Each of those steps may be more complicated or more frustrating for children with ASD and, consequently, the information obtained may be a less reliable measure of affective state.

Limitations

Several limitations must be noted with regard to the present study. First, the sample size for the psychophysiological analyses was relatively small, and the sample size for the correlational analyses of psychophysiological data and EMA data was extremely small. Consequently, results were considered preliminary with regard to affect-modulation of the postauricular reflex and exploratory with regard to the Ecological Momentary Assessment. Additionally, children with cognitive impairment were excluded from the present study so the results are limited to a subset of children with ASD (i.e., higher functioning children). With regard to the EMA procedure, participants were contacted six times over the course of four days. This was a relatively small number of contacts for an EMA study, though there is no evidence to suggest that increasing the number of prompts would have yielded more compelling results. Finally, the automated prompt system facilitated efficient data collection; however, it made it more difficult to ensure that participants completed the surveys right away or to confirm the method by which they filled out the survey (e.g., mobile device or computer).

Future Directions

The use of affect-modulated psychophysiology in the present study represents an important step in adapting a traditional experimental protocol to address research questions

unique to ASD. Future studies may improve the percentage of analyzable data by modifying protocols to provide greater accommodations to participants with ASD (e.g., shortened protocols). The finding that participants with ASD exhibited greater PAR responses to High ASD Interest images, relative to their TD peers, is an important contribution to the literature on positive affect in ASD. Future research may expand on this finding by refining the Social image category to increase the appetitive salience of the social images (e.g., adding pictures of social scenes, rather than just faces) to examine whether greater differences may be observed between groups, across image categories. Similarly, the appetitive salience of the HAI category may be increased by “personalizing” the images to an individual’s CI or PI.

Future research should explore new ways to examine positive affect in ASD, with the specific goal of expanding current conceptualizations about what motivates the behavior of children with ASD. Focusing on positive affect is an important component to understanding the physiological underpinnings of key behaviors in ASD and for developing effective interventions and supportive environments.

EMA should be considered an important and viable method for ASD research. It is being increasingly used in a variety of fields and advances in technology promise to expand the breadth and depth of EMA-acquired data in coming years. ASD research stands to benefit from EMA’s ability to gather data from subjects in naturalistic settings, and innovative research designs incorporating multiple approaches (e.g., physiological, behavioral) will magnify the impact that research has on children and families living with ASD. For example, incorporating technology that records physiological data (e.g., heart rate) along with subjective reports of affective state could enhance future studies on affective functioning in ASD. Effective utilization of technology in ASD-focused EMA protocols

may prove an effective way to collect data from individuals across a broad range of real- world settings (e.g., home, school, recreation) and improve understanding and treatment of challenging behaviors. The technology may also prove useful in gathering data from individuals across a broad range of functioning, whether via non-verbal subjective report, caregiver report, or physiological assessments.

Conclusion

The present study was the first to examine affect-modulation of the postauricular reflex in children with ASD in response to High Autism Interest, Neutral Nonsocial Interest, and Social images. One of the unique contributions of the present study was its emphasis on positive affect and how positive affect relates to the motivation to approach nonsocial, circumscribed interest activities in children with ASD. The trends observed in PAR

responses to HAI, NNI, and Social images, considered alongside the substantial effect sizes for PAR responses to HAI and NNI images, provide initial evidence that the core symptoms of ASD may be influenced by greater approach motivation for images associated with circumscribed interests, rather than aversion to social images. These findings suggest that using visual stimuli that are specifically tailored to core deficits in ASD may be a promising approach to studying positive affect, especially as it relates to motivation for children with ASD to engage in certain behaviors. Additionally, the present study successfully

implemented a low-cost EMA protocol with a broad age-range of children with and without ASD, affirming the feasibility of this important method in ASD research. Overall, findings from the EMA data indicated no group differences in self-reported positive affect; however, there were promising results when psychophysiological data were correlated with frequency

of behavior spent in social and nonsocial activities. In typically developing adolescents, for example, greater positive affect while viewing social images correlated with increased amounts of time spent in social situations in the real world setting. These findings have important implications for future research, especially with regard to improving understanding of the relation between affect and real-world behavior. Finally, the novel integration of psychophysiology and EMA used in the present study represents an important contribution to the literature on affective functioning in children with ASD.

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