Autism spectrum disorders (ASD) are characterized by abnormalities in reciprocal social interaction and communication, and by the presence of restricted and repetitive behaviors (American Psychiatric Association, 1994
). During the past 20 years, the increased use of standardized diagnostic instruments has contributed to significant advances in clinical assessment of ASD. These instruments have sought to operationalize general diagnostic concepts, such as ‘abnormalities in social interaction’, by delineating specific behavioral markers of impaired social reciprocity. Based on DSM-IV criteria, the instruments provide information about particular areas of abnormality, such as limited attempts to direct others’ attention through pointing, showing, or commenting, and decreased awareness of and/or responses to other people, such as not responding to one’s name being called, or not seeking out other children. Scores on these measures thus provide a standardized means of organizing and conceptualizing ASD symptoms by ensuring that children across different sites and settings are assessed using similar sets of behavioral criteria (Risi, et al., 2006
Parent interviews such as the Autism Diagnostic Interview-Revised (Rutter, Le Couteur, & Lord, 2003
) and the Diagnostic Interview for Social and Communication Disorders (DISCO: Wing, Leekam, Libby, Gould, & Larcombe, 2002
) are designed to gather information about a child’s current and past behaviors that may be relevant to a diagnosis of ASD. The ADI-R includes questions about how a child behaves during various social situations, such as “When your child is excited, how does he share those feelings with you?”, or “How does your child respond when another child approaches him/her?” (ADI-R: Rutter, et al., 2003
). Alternatively, tools like the Autism Diagnostic Observation Schedule (ADOS: Lord et al., 2000
), the Screening Tool for Autism in Two Year Olds (STAT: Stone, Coonrod, & Ousley, 2000
), and the Autism Observation Scale for Infants (AOSI: Bryson, Zwaigenbaum, McDermott, Rombough, & Brian, 2008
) provide an opportunity for the clinician to directly observe the child’s social interchanges with an unfamiliar adult, and in some cases, with a parent. In the ADOS, the clinician presents a standard set of activities or questions that are intended to elicit a variety of behaviors and emotional reactions from the child. The clinician then scores his/her observations of these behaviors immediately following the assessment (Gotham, Risi, Pickles, & Lord, 2007
; Lord, et al., 2000
). In the “Shared Enjoyment” code, for example, the clinician determines a score based on how well the child was able to indicate pleasure during interactions with the examiner. In the case of a young child, a clear indication of sharing enjoyment might be smiling at the examiner and saying “Wow Bubbles” when the examiner blows bubbles. Shared enjoyment that might be observed in an older child could include a visible demonstration of enthusiasm (e.g., smiling, leaning forward in his chair attentively, laughing) as the child relates vacation stories to the examiner. On the other hand, a child would not be rated as sharing enjoyment if he or she exhibited only neutral facial expressions in response to new toys and activities presented by the examiner, or if he responded to the examiner’s attempts to initiate conversation without eye contact and with brief, monotone responses that seemed to indicate a lack of interest.
Standardized diagnostic instruments such as the ADI-R and ADOS are designed to be administered by clinicians trained in ASD diagnostic practices and in coding procedures specific to each of the measures. Unlike symptom checklists that indicate only whether a certain symptom is present or absent, these investigator-based instruments offer clinicians the flexibility to employ their clinical experience to make judgments about symptoms in the context of other behaviors, and to use different clinical skills to gather information needed to derive an overall clinical diagnosis. However, whereas built-in flexibility and reliance on the clinical skills of the examiner are necessary in the context of diagnostic assessment, these features present significant challenges for research aimed at understanding the etiology of ASD. Thus, while these instruments have undoubtedly moved the field toward thinking more specifically about the particular behavioral markers that characterize the ASD phenotype(s), behavioral codes yielded by the instruments’ are still relatively broad and do not readily map onto underlying mechanisms (see also Klin, 2008
Just as the clinical diagnosis of ASD now relies on standardized diagnostic instruments that incorporate a variety of measures of social impairment, evaluations of mouse genetic and toxicological models need to be assessed for an array of distinct social deficits, including sociality, social interaction, social motivation, acoustic communication, and empathy. In the absence of biomarkers that can be used to diagnose ASD, both human and animal researchers are highly dependent upon behavioral observation methodology to characterize their samples. Therefore, in order to more effectively coordinate ASD phenotyping research with basic science investigations into the causes of ASD-related impairments, there is clearly a need to develop and apply novel assessment methods that can be more readily employed to achieve translational research goals (e.g., Klin, Jones, Schultz, Volkmar, & Cohen, 2002
This paper represents collaboration between a clinical psychologist whose research focuses on assessment of the behavioral phenotypes of children with ASD, and an expert in mouse social behavior who has designed novel behavioral measures of social motivation and communication in mice. We hope that our dialogue can contribute to ongoing efforts to coordinate animal model and clinical research efforts (Lahvis, Alleva, & Scattoni, 2010
; Silverman, Yang, Lord, & Crawley, 2010
) to identify the underlying causes of ASD.
For the purposes of this discussion, we focus on the issue of impaired shared affect in ASD, which is arguably one of the most central and defining features of the disorder (e.g., Dawson, Hill, Spencer, Galpert, & Watson, 1990
; Kanner, 1943
; Wing & Gould, 1979
; Yirmiya, Kasari, Sigman, & Mundy, 1989
). Shared affect can be conceptualized in terms of a “Reciprocity Chain.” As with previously proposed organizational structures, such as the Social Information Processing Network (SIPN: Nelson, Leibenluft, McClure, & Pine, 2005
), the Reciprocity Chain can be used to translate and extend current ASD diagnostic instruments, with their considerable dependence upon clinician insight, to a useful scientific framework. The Reciprocity Chain isolates shared affect into a linked interplay of four components (see ).
Measurable features of the reciprocity chain include the expression of emotion by individual A and individual B’s ability to physiologically and behaviorally respond to these expressions. Using the Reciprocity Chain as an organizing structure, we will contrast typical human development with ASD, and then examine ways that the broad concept of shared affect might be reduced to elements that can be studied as minimal functional units of behavior in mouse development. Through this process, we hope to draw clear links between relevant human behaviors and potential opportunities to measure those same behaviors in mice.