Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by persistent deficits in social-emotional reciprocity as well as the presence of restricted and repetitive behaviors and interests (RRBI) [1]. In the Diagnostic and Statistical Manual (DSM-V), ASD is defined as a spectrum of behaviors marked by heterogenous core and co-occurring features [1], diagnosable according to behaviorally defined criteria [2] by trained clinicians. A full diagnostic assessment involves several hours of expert clinician time and standardized assessments; however, studies indicate that nearly all clinicians (97%) report forming an immediate, strong impression of diagnostic status in many cases [3]. Such impressions are generally consistent with gold-standard diagnoses [4]. This impression represents the distinct behavioral presentation of a subset of autistic individuals, dubbed “frank autism,” purportedly recognizable within minutes. The current study evaluates the consistency of frank autism impressions in adolescents and young adults, including impressions of a group of individuals diagnosed early in life who no longer display autism symptoms, and compares them to gold-standard diagnostic classifications. We also characterize the behavioral factors that contribute to clinician impressions of autism, to better understand how frank autism impressions relate to enduring, core symptoms, and discuss how the presence of “frank autism” relates to the construct of “prototypical autism” [5]. Note that person-first and identity-first language will both be used in this manuscript to acknowledge the diverse preferences within the autism community [6, 7]; in addition, we limit the use of language consistent with the medical model of autism (e.g., “symptoms” and “deficits”) in our discussion of diagnostic criteria.

DSM-V ASD diagnostic criteria can differentiate autistic individuals from non-autistic individuals and capture the wide variability within the autism spectrum [8]. Indeed, autism is one of the most reliable diagnoses in the DSM-V [9] with Kappa values from 0.60 to ≥ 0.80 (considered moderate to substantial agreement). A study assessing expert clinician team-based diagnoses reported that some clinicians relied heavily on “feeling autism in the encounter,” along with quality of collateral report from parents, to inform diagnostic decisions [10]. However, a study utilizing expert clinician consensus to evaluate the reliability of evaluations performed by community clinicians without ASD-specific expertise found suboptimal agreement on diagnostic status [11]. Of the 87 children and young adults, ages 2–25 years, with community ASD diagnoses, 23% were classified by expert clinician consensus as not autistic, illustrating a discrepancy in diagnostic judgments based on available resources (e.g., time, access to diagnostic tools, expert consultation, etc.) and clinician training.

In one study of frank autism, licensed psychologists watched 10-minute video clips of another clinician administering the Autism Diagnostic Observation Schedule [12] to 42 toddlers who had been flagged with possible ASD during screening [13]. After watching a 10-minute clip, clinicians indicated whether they would refer the child for a comprehensive ASD-specific assessment; two referral decisions were made per child by different clinicians (84 total videos). In this sample, 17 (61%) were referred by one or both clinicians for further ASD assessment and ultimately diagnosed with ASD; seven (25%) were referred by one or both clinicians, but ultimately diagnosed with language delays but not autism; and three (11%) were referred by one or both clinicians, but ultimately found to be typically developing, indicating sensitivity of 0.61 and specificity of 0.82. Of the 57 videos for which neither clinician recommended an ASD-specific evaluation, 11 (39%) were ultimately diagnosed with ASD (i.e., these cases were missed by the observing clinicians). These findings suggest that trained clinicians can identify and distinguish autistic symptoms from characteristics of other developmental delays in toddlers with some accuracy, based on 10 min of behavioral observation. However, the high number of false negatives suggests that this information alone is insufficient, at least in the case of toddlers. Furthermore, the determination needed in a clinical evaluation requires not just ruling autism in or out, but also differentiating between autism and other conditions – a significantly more challenging endeavor.

A related study explored the initial impressions of trained clinicians for a sample of 294 children ages 1–4 years who were referred for a diagnostic evaluation after being flagged as at-risk for autism on a brief parent-report screener [4]. After five minutes of interaction during the diagnostic evaluation, clinicians paused and indicated their initial diagnostic impression (ASD or non-ASD) and rated their confidence in this initial impression. Results showed that 238 (81%) initial clinical impressions were concordant with the final diagnosis; the autism cases were judged more accurately than the non-ASD cases, with 86 (92%) of the ASD impressions ultimately receiving an autism diagnosis, consistent with a frank autism phenotype. There was a high false negative or “missed cases” rate: 49 (24%) cases initially viewed as not autism ultimately received an ASD diagnosis; false positive rates were far lower (7%). Clinicians were confident in their initial impressions, particularly for non-autistic cases, with an average confidence rating of 3.74 out of 5. These results highlight the ability of trained clinicians to detect ASD from brief behavioral observation, but underscore that some young autistic children (e.g., 18% in this sample) would be missed by an initial diagnostic impression.

A recent study by the same group [14] further explored what behavioral characteristics informed diagnostic impressions within the first five minutes of interaction with 55 toddlers (mean age = 22.9 months) referred for a developmental evaluation due to parent or pediatrician concerns for autism-related behaviors. Junior (e.g., graduate student) and senior (e.g., PhD level) clinicians were asked to rate their diagnostic impression (autistic or non-autistic), their confidence in this impression, and what behaviors contributed to their impression. Consistent with prior findings, clinicians rated 63% of cases that ultimately received an autism diagnosis as autistic and 100% of cases that did not receive an autism diagnosis as non-autistic. Both junior and senior clinicians relied on social reciprocity, nonverbal communication, and eye contact to form accurate initial impressions. Additionally, senior clinicians relied on the child’s focus of attention in forming accurate impressions of both autistic and non-autistic children, whereas junior clinicians only relied on this behavior in forming accurate impressions of non-autistic children. These results are the first to explore the behaviors that contribute to diagnostic impressions during brief clinical interactions with young children.

The prevalence of first-time diagnostic evaluations of adolescents and adults has significantly increased in the past decade, in part because of changes in awareness, diagnostic criteria, and professional practice [15, 16]. The assessment of older individuals provides a unique set of challenges that are not present when assessing young children. Typical diagnostic practice relies heavily on parent or caregiver report of the early developmental history of the individual, which may be difficult to obtain or inaccurately recalled years later [15, 17, 18]; it can also display “telescoping” effects, such that caregivers of individuals who currently display stronger adaptive skills are more likely to recall more strengths and fewer delays in early development [19]. This lack of clear developmental history may force clinicians to rely more heavily on current behavioral observation alone. This, in combination with the evidence that some clinicians rely on less operationalized behavioral observations, by “feeling autism in the encounter” [10], may lead some autistic adults to receive an official diagnosis of autism more readily than others. To date, no studies have explored the behavioral factors that impact clinician impressions of autistic adults.

Despite clinical and empirical evidence regarding the good reliability of brief initial impression, the specific factors that contribute to this impression in adolescents and adults are unknown. The initial study proposing frank autism [3] surveyed 151 clinicians with autism-specific expertise about their representation and usage of this construct. Results showed that nearly all (97%) believed that something like frank autism exists, and that they could determine whether an individual fits the phenotype of frank autism in roughly the first ten minutes of interaction or observation. The clinicians who were familiar with the construct estimated that roughly 40% of the ASD population exhibits the frank autism phenotype. Clinicians also reported that the most common specific behaviors associated with this phenotype included impairments or atypicalities in reciprocity, vocal prosody, eye contact, motor mannerisms (such as stereotypies), and gait or posture. These findings highlight factors that may impact initial impressions during ASD diagnostic decision making. To date, no studies have empirically tested the endorsements of these behaviors associated with correct or incorrect frank autism impressions in adults.

Gestures, facial expressions, eye contact, vocal prosody, and social reciprocity have each been implicated as atypical in autistic individuals, and relevant for difficulties with social functioning. Compared to neurotypical peers, autistic individuals produce semantically, pragmatically, and motorically atypical gestures [20,21,22,23,24,25], as well as atypical facial expressions [26, 27], eye contact [28], and vocal prosody [29, 30]. Together, these characteristics may negatively impact autistic individuals’ social interactions and elicit impressions of social awkwardness from naïve observers [26, 27, 29, 31]. Initial impressions for expert clinicians and naïve laypeople may reflect similar processes, despite differences in rater goals (e.g., motivation to engage in future social interaction, versus clinical motivation to arrive at an accurate diagnosis) and the nature of ratings (Likert scales measuring the likeliness that an individual has friends versus binary diagnostic ratings).

In summary, the construct of frank autism is widely assumed in clinical practice and is relevant for initial impressions of behavioral atypicalities in non-clinical settings. As such, it is important to establish which behavioral factors contribute to this impression, as they likely have implications for diagnostic decision making (e.g., who is ultimately diagnosed with autism), as well as clinical management.

Although developmental disorders are typically seen as life-long conditions, a series of studies has identified and characterized a group of individuals who were diagnosed with autism in childhood but who no longer meet DSM-V criteria in adolescence, based on ADOS-2 observations, parent and child symptom report, and clinical best estimate. Estimates suggest that 3–25% of children diagnosed with ASD in early childhood fall into this category [32] by adolescence, although a recent study reported that 37% of toddlers diagnosed with ASD lost the diagnosis by early school age [33]. Our research team has extensively studied these types of individuals [34]. Findings indicate that in early development, the “loss of autism diagnosis” (LAD) group had milder symptoms in the social domain, compared to an age-matched currently autistic group, but equally significant difficulties with communication and repetitive behaviors, including the presence of early language delays. Tests of current functioning indicated that, compared to age- and IQ-matched children with a current autism diagnosis and with neurotypical (NT) children with no history of autism, the LAD group had typical or above-average scores on standardized and experimental assessments of language [35,36,37,38,39], social skills [40, 41], and restricted and repetitive behaviors [42]. To date, no studies have explored frank autism in LAD, and whether these individuals present with subtle or overt frank autism behaviors during initial interactions; findings would help to establish the degree to which these individuals continue to display subtle behavioral characteristics of autism. More broadly, understanding frank autism in LAD may be useful in addressing controversies about the nature of the autism diagnosis [43, 44]. For example, Mottron and colleagues have suggested that developing more constrained diagnostic criteria for autism, informed by strong developmental history data, would facilitate clinical ascertainment and homogeneity of research samples [5, 45].

The current study had three pre-registered aims (see https://osf.io/5tkrn/?view_only=1f0b6bf70d7d4bab9ebf22da7603e647). Our first aim was to evaluate group (autism, LAD, NT) differences in frank autism impressions made by seven graduate-level (clinical psychology PhD student) and two expert PhD-level clinicians as a predictor of current gold-standard diagnosis in an adolescent and young adult sample. Based on prior studies of LAD and autism, we predicted significantly reduced ASD-like impressions in the LAD and NT groups relative to the autism group, and significant positive correlations between initial impressions of frank autism and ADOS-2 Calibrated Severity Scores (CSS).

Second, drawing on the prior frank autism studies of young children, we asked which behaviors were the most salient contributors to frank autism impressions, by assessing rates of atypicality in gesture, eye contact, motor mannerisms, prosody, facial expressions, attentional focus, and shifting attention (including perseverative thinking and distractibility), social reciprocity, and social initiations. We predicted significantly higher (more atypical) ratings for gesture, eye contact, motor mannerisms, prosody, facial expressions, and social reciprocity. We also predicted that attentional focus and social initiations would be similar across groups, as prior literature typically implicates these more infrequent behaviors (that may be difficult to perceive during a brief encounter) as less consistently associated with a frank autistic presentation.

Third, we hypothesized high overall confidence (e.g., 3 or above on a scale of 1–5) in initial impressions, with higher ratings for NT individuals that had never received an autism diagnosis (based on Wieckowski et al., 2021). We also predicted that the confidence ratings for the LAD group would be significantly lower than both the ASD and NT groups due to possible subclinical social impairments. We hypothesized that higher confidence would be significantly associated with eye contact, motor mannerisms, prosody, and social reciprocity, but not gesture, facial expressions, focus/shifting of attention, or social interactions.