Lovaas technique
Encyclopedia
LOVAAS technique, which is known to the general public as Applied behavior analysis
(ABA), as well as Intensive behavioral intervention (IBI), and Early intensive behavioral intervention (EIBI), is a form of treatment guided by ABA and developed by Dr. Ivar Lovaas
, a psychology professor at UCLA. It is an early intervention therapy designed for children diagnosed with autism
or related disorders. The technique consists of an intensive behavioral intervention which is carried out early in the development of autistic children. It involves discrete-trial teaching, breaking skills down into their most basic components and rewarding positive performance. It is also known for its previous use of aversives
to punish
unwanted behaviors.
") behavior, teaches imitation, establishes playing with toys in their intended manner, and integration of the family into the treatment protocol. The second year teaches early expressive and abstract linguistic skills, peer interaction, basic socializing skills, and strives to include the individual's community in the treatment to optimize mainstreaming while eliminating any possible sources of stigmatization. The third year focuses on emotional expression and variation in addition to observational learning, and pre-academic skills such as reading writing, and arithmetic. Rarely is the technique implemented for the first time with adults.
The Lovaas method is ideally performed five to seven days a week with each session lasting from five to seven hours, totaling an average of 35–40 hours per week. Each session is divided into trials with intermittent breaks. The trials do not have a specified time limit to allow for a natural conclusion when the communicator feels the child is losing focus. Each trial is composed of a series of prompt
s (verbal, gestural
, physical
, etc.) that are issued by the “communicator” who is positioned directly across the table from the individual receiving treatment. These prompts can range from “put in”,” put on”,” show me”,” give to me” and so on, in reference to an object, color, simple imitative gesture
, etc. The concept is centered on shaping
the child to correctly respond to the prompts, increasing the attentive ability of the individual, and mainstreaming the child for academic success. Should the child fail to respond to a prompt, a “prompter,” seated behind the child, uses either a partial-, a simple nudge or touch on the hand or arm or a full-, hand over hand assistance until the prompt has been completed, physical guide to correct the individual’s mistake or non-compliance. Each correct response is reinforced with verbal praise, an edible, time with a preferred toy, or any combination thereof. DTT is often used in conjunction with the Picture Exchange Communication System (PECS) as it primes the child for an easy transition between treatment types. The PECS program serves as another common intervention technique used to mainstream individuals with autism. As much as 25% of the autistic population has no functional speech, the remainder typically display pronounced phonological and grammatical deficits in addition to a limited vocabulary. The program teaches spontaneous social communication through symbols and/or pictures by relying on ABA techniques. PECS operates on a similar premise to DTT in that it uses systematic chaining
to teach the individual to pair the concept of expressive speech with an object. It is structured in a similar fashion to DTT, in that each session begins with a preferred reinforcer survey to ascertain what would most motivate the child and effectively facilitate learning.
Lovaas was developed based on research performed by Lovaas and his assistants. This research reported that 47% of those children that had received an average of 40 hours of intensive therapy were mainstreamed into regular classrooms, and were classified as "indistinguishable" from their peers in follow-up studies. Although subsequent studies have shown that intensive behavioral therapy clearly benefited children with autism, it has been claimed that Lovaas's original claims of effectiveness were overstated. A 2005 California study found that early intensive behavior analytic treatment, a form of ABA, was substantially more effective for preschool children with autism than the mixture of methods provided in many programs; this study did not use random assignment or a uniform assessment protocol, and provided limited information about the intervention, making it difficult to replicate.
Smith et al. (2002) performed a preliminary study of nine high-functioning autistic children, all of whom were previous recipients of early intensive behavioral intervention (EIBI), of ages five to seven in free play settings. The purpose was to assess the effects of EIBI on solitary activities, ritualistic behaviors, and social activity when exposed to the two experimental groups. Each child participated in four, one hour sessions consisting of 15 minute periods of play with either a typically developing peer or a lower functioning autistic child with major deficits in pragmatic communication, social interaction and self-care. Children had never met prior. The period of play began with 15 minutes of play with either the typically developed (TD) peer or the developmentally disabled (DD) peer and alternated accordingly in one of two variations: TD-DD-TD-DD or DD-TD-DD-TD. Observers rated play on five criterion: i. interactive toy play, ii. interactive speech, iii. solitary toy play, iv. solitary speech, and v. self-stimulation. Data showed the high-functioning children displayed significantly more instances of interactive play and interactive speech when paired with the typically developed.
The Lovaas Technique is best generalized when paired with natural settings, and the implementation is clearly structured. A good sense of direction is needed when planning for intervention. Although this is one approach, many children with autism spectrum disorder learn differently and this needs to be taken into account to ensure the Lovaas approach is effective for all. For some children it is shown that typical peer interaction can increase an autistic child's chances of leading a normal life. Lovaas Techniques are cost effective for administrators.
such as striking, shouting, or using electrical shocks. These procedures have been widely abandoned for over a decade. A review of literature by autistic activist Michelle Dawson
asserts that the method has become less effective since these stimuli were abandoned. Only one institution, the Judge Rotenberg Center, still employs electric shocks as aversives—a practice that continues to cause them considerable legal and political controversy. This has led some to question whether behavioral techniques should be limited to those who are licensed (see licensed behavior analyst)
Another study estimated the expenses of a three year period of DTT to total a conservative cost of $20,000 and the extreme cost of $60,000, with a yearly average of $40,000. These costs were based on a sliding scale model that would be adjusted accordingly to socio-economic status and parental involvement. Yearly expenditures were predicted to drop to an average of $22,500 a year when parents and family became involved in the process. Additional family involvement would subsequently alleviate case manager and paraprofessional hours by assuming their roles in the process. The upfront costs of DTT for the state of Texas would initially amount to $67,500 for three years compared to the currently state budgeted $33,000 for Special Education. The difference is predicted to be recovered within five years of the initial implementation of the program. Texas would experience a 72% reduction in expenses in the 15 year offset following the conclusion of DTT, amounting to a total savings of $84,300 per child.
However, the federal law called the Individuals with Disabilities Education Act (IDEA) requires school districts to provide a Free and Appropriate Public Education (FAPE) to all children over the age of three. Many Due Process and court decisions have found 35–40 hours per week of ABA to be FAPE. Parents may wish to consider hiring and attorney or advocate if their school district denies ABA treatment.
Thomas et al. (2007) conducted a survey study that involved 383 families with children diagnosed with autistic spectrum disorder from North Carolina. Three quarters of these families reported using a major treatment plan. Of these, college or graduate degree holding parents were two to four times more likely to use a neurologist and/or PECS. Annual incomes of $50,000 or more had higher rates of using developmental pediatricians and speech/language therapists. Racial and ethnic minorities were half as likely to see a case manager. These families also had a quarter of the odds of seeing a psychologist, developmental pediatrician, or implementing sensory integration. This supports several other national studies that concluded racial and ethnic families, parents with a low degree of education, and those not residing in a metropolitan area were more likely to receive limited care, utilize a less diverse range of services and less likely to follow a major treatment plan. Both the national studies and the North Carolinian study yielded a correlation between high stress levels and amount of services sought.
Families that did not identify with a major treatment approach had one fifth to one half the odds of using support of friends and family in providing care. Therapeutic support services (PECS, parent support classes, sensory integration, casein- and gluten-free diets) were also one fifth to one half as likely to be used compared to families identifying with major treatment plans.
Insurance coverage is another major determinant in the amount of support services received. Recipients of Medicaid or other forms of public health insurance have 2-11 times the odds of using services that are considered medically necessary. Utilization of respite, PECS, case managers, speech or language therapists also increases markedly in this bracket compared to families with private insurance.
Rising costs in education and the provision of adequate care for developmentally disabled individuals have been a continuing concern for state policy makers and tax payers alike. A study was conducted on cost comparison of 18 years of traditional Special Education on Early Intensive Behavioral Intervention (EIBI) for autistic children. The Texas state budget for the year 2002 allotted $11,000 per child for Special Education. The study suggested the state would save an average of $208,500 per child over an 18 year period by implementing DTT in early childhood, effectively curbing or eliminating future special needs costs by preparing the child academically for mainstreaming. This amounted to a potential total savings of $2.9 billion over an 18 year period for a cohort consisting of 10,000 autistic children.
al design of matched pairs regarding the distribution of subjects within the experimental and control groups. Gresham and MacMillar (1998) also state a lack of a true representation of autism in that the subjects were neither randomly sampled from the cumulative autistic population nor were they randomly assigned to treatment groups. The internal validity
of the study was also called into question due to the possibility of skewed data resulting from three influential threats. Instrumentation, changes or variations in measurement of procedures over time, was argued to have been altered in both the pre-test and post-test conditions which were confounded by a differentiation in ascertaining cognitive abilities and intelligence of the subjects. The pre-test utilized four measures of cognitive ability and mental development. Five of the subjects' intelligence was determined through a parent-reported measure of adaptive behavior. All of the subjects were post-tested three years later using five other measures of intelligence and cognitive ability. Long-term follow-up was assessed with three measurements of (1) intelligence, (2) nonverbal reasoning, and (3) receptive language. The original three measurements during the testing phase were determined by (1) IQ score, (2) class placement, and (3) promotion/retention. External validity was called into question concerning sample characteristics. Lovaas' (1987) criteria for acceptance into the program required a psychological mental age greater than 11 months and a chronological age less than 46 months in the case of echolalic
children. Schopler et al. (1989) purport that if both the intellectual and echolalia criteria were rigidly adhered to at the North Carolina institute, approximately 57% of the referrals would have been excluded from the program.
Other criticisms include a failure to operationally define the use of the term 'reinforcement' for compliance, the use of a Pro-rated Mental Age, and the statistical regression of the child's IQ over time. Boyd (1998) addressed the potential impact of a disproportionate sex ratio
of females to males on the control group's mean IQ score. Females with autism typically display slightly lower levels of functioning in comparison to their male counterparts.
In a rejoinder to Boyd's (1998) article that cited an unequal sex ratio as a source of error, Lovaas (1998) listed three reasons as to why the disporportionate ratio's influence on the data was negligible. The autistic population at the time had a ratio of 4:1. Lovaas (1998) argued that the ratios for the experimental group, control group 1, and control group 2 of 16:3, 11:8, and 16:5, respectively, were in fact near the expected ratio scale of the general population with the exception of control group 1. The second argument lay in the studies Boyd (1998) referenced in regards to low intellectual performance in females diagnosed with autism. One of the studies admitted to having a female subject with Rett disorder, a condition that showed little responsiveness to intensive early behavioral intervention. Lovaas (1998) concluded by proposing that males may more readily meet diagnostic criteria for autism because of certain salient characteristics inherent in the sex while the subtleties in their female counterparts may be overlooked.
Applied Behavior Analysis
Applied behavior analysis is a science that involves using modern behavioral learning theory to modify behaviors. Behavior analysts reject the use of hypothetical constructs and focus on the observable relationship of behavior to the environment...
(ABA), as well as Intensive behavioral intervention (IBI), and Early intensive behavioral intervention (EIBI), is a form of treatment guided by ABA and developed by Dr. Ivar Lovaas
Ole Ivar Lovaas
Ole Ivar Løvaas, Ph.D. was a clinical psychologist at UCLA. He is considered to be one of the fathers of applied behavior analysis therapy for autism through his development of the Lovaas technique and the first to provide evidence that the behavior of autistic children can be modified through...
, a psychology professor at UCLA. It is an early intervention therapy designed for children diagnosed with autism
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
or related disorders. The technique consists of an intensive behavioral intervention which is carried out early in the development of autistic children. It involves discrete-trial teaching, breaking skills down into their most basic components and rewarding positive performance. It is also known for its previous use of aversives
Aversives
In psychology, aversives are unpleasant stimuli that induce changes in behavior through punishment; by applying an aversive immediately following a behavior, the likelihood of the behavior occurring in the future is reduced. Aversives can vary from being slightly unpleasant or irritating to...
to punish
Punishment (psychology)
In operant conditioning, punishment is any change in a human or animal's surroundings that occurs after a given behavior or response which reduces the likelihood of that behavior occurring again in the future. As with reinforcement, it is the behavior, not the animal, that is punished...
unwanted behaviors.
Implementation
The Lovaas approach is a highly structured comprehensive program that relies heavily on discrete trial training (DTT) methods. Within Lovaas therapy, DTT is used to reduce stereotypical autistic behaviours through extinction and the provision of socially acceptable alternatives to self-stimulatory behaviors. Intervention can start when a child is as young as three and can last from two to six years. The first year seeks to reduce self-stimulating ("stimmingStimming
Stimming is a repetitive body movement, such as hand flapping, that is hypothesized to stimulate one or more senses. The term is shorthand for self-stimulation. Repetitive movement, or stereotypy, is often referred to as stimming under the hypothesis that it has a function related to sensory input....
") behavior, teaches imitation, establishes playing with toys in their intended manner, and integration of the family into the treatment protocol. The second year teaches early expressive and abstract linguistic skills, peer interaction, basic socializing skills, and strives to include the individual's community in the treatment to optimize mainstreaming while eliminating any possible sources of stigmatization. The third year focuses on emotional expression and variation in addition to observational learning, and pre-academic skills such as reading writing, and arithmetic. Rarely is the technique implemented for the first time with adults.
The Lovaas method is ideally performed five to seven days a week with each session lasting from five to seven hours, totaling an average of 35–40 hours per week. Each session is divided into trials with intermittent breaks. The trials do not have a specified time limit to allow for a natural conclusion when the communicator feels the child is losing focus. Each trial is composed of a series of prompt
Prompt
Prompt may refer to:* Command prompt, in computing, one or more characters in a command line interface to indicate that the computer is ready to accept typed input...
s (verbal, gestural
Gesture
A gesture is a form of non-verbal communication in which visible bodily actions communicate particular messages, either in place of speech or together and in parallel with spoken words. Gestures include movement of the hands, face, or other parts of the body...
, physical
Physical
Physical may refer to:*Body, the physical structure of an organism**Human body, the physical structure of a human*Physical abuse, abuse involving contact intended to cause feelings of intimidation, injury, or other physical suffering or bodily harm...
, etc.) that are issued by the “communicator” who is positioned directly across the table from the individual receiving treatment. These prompts can range from “put in”,” put on”,” show me”,” give to me” and so on, in reference to an object, color, simple imitative gesture
Gesture
A gesture is a form of non-verbal communication in which visible bodily actions communicate particular messages, either in place of speech or together and in parallel with spoken words. Gestures include movement of the hands, face, or other parts of the body...
, etc. The concept is centered on shaping
Shaping
Shaping can refer to:* In electricity generation, maintaining reliable delivery, for example by use of pumped storage hydroelectricity* Shaping , the reinforcement of successive approximations to train a type of behavior...
the child to correctly respond to the prompts, increasing the attentive ability of the individual, and mainstreaming the child for academic success. Should the child fail to respond to a prompt, a “prompter,” seated behind the child, uses either a partial-, a simple nudge or touch on the hand or arm or a full-, hand over hand assistance until the prompt has been completed, physical guide to correct the individual’s mistake or non-compliance. Each correct response is reinforced with verbal praise, an edible, time with a preferred toy, or any combination thereof. DTT is often used in conjunction with the Picture Exchange Communication System (PECS) as it primes the child for an easy transition between treatment types. The PECS program serves as another common intervention technique used to mainstream individuals with autism. As much as 25% of the autistic population has no functional speech, the remainder typically display pronounced phonological and grammatical deficits in addition to a limited vocabulary. The program teaches spontaneous social communication through symbols and/or pictures by relying on ABA techniques. PECS operates on a similar premise to DTT in that it uses systematic chaining
Chaining
Chaining is an instructional procedure used in behavioral psychology, experimental analysis of behavior and applied behavior analysis. It involves reinforcing individual responses occurring in a sequence to form a complex behavior. It is frequently used for training behavioral sequences that are...
to teach the individual to pair the concept of expressive speech with an object. It is structured in a similar fashion to DTT, in that each session begins with a preferred reinforcer survey to ascertain what would most motivate the child and effectively facilitate learning.
Effectiveness
Over 500 articles have been published showing the effectiveness of Lovaas technique for children with autism. Effectiveness questions appear to arise around specific claims of recovery from autism based on the intervention.Lovaas was developed based on research performed by Lovaas and his assistants. This research reported that 47% of those children that had received an average of 40 hours of intensive therapy were mainstreamed into regular classrooms, and were classified as "indistinguishable" from their peers in follow-up studies. Although subsequent studies have shown that intensive behavioral therapy clearly benefited children with autism, it has been claimed that Lovaas's original claims of effectiveness were overstated. A 2005 California study found that early intensive behavior analytic treatment, a form of ABA, was substantially more effective for preschool children with autism than the mixture of methods provided in many programs; this study did not use random assignment or a uniform assessment protocol, and provided limited information about the intervention, making it difficult to replicate.
Smith et al. (2002) performed a preliminary study of nine high-functioning autistic children, all of whom were previous recipients of early intensive behavioral intervention (EIBI), of ages five to seven in free play settings. The purpose was to assess the effects of EIBI on solitary activities, ritualistic behaviors, and social activity when exposed to the two experimental groups. Each child participated in four, one hour sessions consisting of 15 minute periods of play with either a typically developing peer or a lower functioning autistic child with major deficits in pragmatic communication, social interaction and self-care. Children had never met prior. The period of play began with 15 minutes of play with either the typically developed (TD) peer or the developmentally disabled (DD) peer and alternated accordingly in one of two variations: TD-DD-TD-DD or DD-TD-DD-TD. Observers rated play on five criterion: i. interactive toy play, ii. interactive speech, iii. solitary toy play, iv. solitary speech, and v. self-stimulation. Data showed the high-functioning children displayed significantly more instances of interactive play and interactive speech when paired with the typically developed.
The Lovaas Technique is best generalized when paired with natural settings, and the implementation is clearly structured. A good sense of direction is needed when planning for intervention. Although this is one approach, many children with autism spectrum disorder learn differently and this needs to be taken into account to ensure the Lovaas approach is effective for all. For some children it is shown that typical peer interaction can increase an autistic child's chances of leading a normal life. Lovaas Techniques are cost effective for administrators.
Aversives
While the therapy has always relied principally on positive reinforcement of preferred behavior, Lovaas's original technique also included more extensive use of aversivesAversives
In psychology, aversives are unpleasant stimuli that induce changes in behavior through punishment; by applying an aversive immediately following a behavior, the likelihood of the behavior occurring in the future is reduced. Aversives can vary from being slightly unpleasant or irritating to...
such as striking, shouting, or using electrical shocks. These procedures have been widely abandoned for over a decade. A review of literature by autistic activist Michelle Dawson
Michelle Dawson
Michelle Dawson is an individual diagnosed with autism and an autism researcher. She has written a paper challenging the ethical and scientific foundations of Applied Behavior Analysis -based autism interventions. She also challenged the medical necessity of ABA for individuals with autism in...
asserts that the method has become less effective since these stimuli were abandoned. Only one institution, the Judge Rotenberg Center, still employs electric shocks as aversives—a practice that continues to cause them considerable legal and political controversy. This has led some to question whether behavioral techniques should be limited to those who are licensed (see licensed behavior analyst)
Cost of Care
A concern that parents have brought up regarding Lovaas is the cost, which in April 2002 amounted to about US$4,200 per month ($50,000 annually per child). In addition, the 20–40 hours per week intensity of the program, often conducted at home, may place additional stress on already challenged families.Another study estimated the expenses of a three year period of DTT to total a conservative cost of $20,000 and the extreme cost of $60,000, with a yearly average of $40,000. These costs were based on a sliding scale model that would be adjusted accordingly to socio-economic status and parental involvement. Yearly expenditures were predicted to drop to an average of $22,500 a year when parents and family became involved in the process. Additional family involvement would subsequently alleviate case manager and paraprofessional hours by assuming their roles in the process. The upfront costs of DTT for the state of Texas would initially amount to $67,500 for three years compared to the currently state budgeted $33,000 for Special Education. The difference is predicted to be recovered within five years of the initial implementation of the program. Texas would experience a 72% reduction in expenses in the 15 year offset following the conclusion of DTT, amounting to a total savings of $84,300 per child.
However, the federal law called the Individuals with Disabilities Education Act (IDEA) requires school districts to provide a Free and Appropriate Public Education (FAPE) to all children over the age of three. Many Due Process and court decisions have found 35–40 hours per week of ABA to be FAPE. Parents may wish to consider hiring and attorney or advocate if their school district denies ABA treatment.
Thomas et al. (2007) conducted a survey study that involved 383 families with children diagnosed with autistic spectrum disorder from North Carolina. Three quarters of these families reported using a major treatment plan. Of these, college or graduate degree holding parents were two to four times more likely to use a neurologist and/or PECS. Annual incomes of $50,000 or more had higher rates of using developmental pediatricians and speech/language therapists. Racial and ethnic minorities were half as likely to see a case manager. These families also had a quarter of the odds of seeing a psychologist, developmental pediatrician, or implementing sensory integration. This supports several other national studies that concluded racial and ethnic families, parents with a low degree of education, and those not residing in a metropolitan area were more likely to receive limited care, utilize a less diverse range of services and less likely to follow a major treatment plan. Both the national studies and the North Carolinian study yielded a correlation between high stress levels and amount of services sought.
Families that did not identify with a major treatment approach had one fifth to one half the odds of using support of friends and family in providing care. Therapeutic support services (PECS, parent support classes, sensory integration, casein- and gluten-free diets) were also one fifth to one half as likely to be used compared to families identifying with major treatment plans.
Insurance coverage is another major determinant in the amount of support services received. Recipients of Medicaid or other forms of public health insurance have 2-11 times the odds of using services that are considered medically necessary. Utilization of respite, PECS, case managers, speech or language therapists also increases markedly in this bracket compared to families with private insurance.
Rising costs in education and the provision of adequate care for developmentally disabled individuals have been a continuing concern for state policy makers and tax payers alike. A study was conducted on cost comparison of 18 years of traditional Special Education on Early Intensive Behavioral Intervention (EIBI) for autistic children. The Texas state budget for the year 2002 allotted $11,000 per child for Special Education. The study suggested the state would save an average of $208,500 per child over an 18 year period by implementing DTT in early childhood, effectively curbing or eliminating future special needs costs by preparing the child academically for mainstreaming. This amounted to a potential total savings of $2.9 billion over an 18 year period for a cohort consisting of 10,000 autistic children.
Criticisms
Gresham and MacMillar (1998) specifically cite a lack of a true experimental design in Lovaas' (1987) experiment on early intervention. They charge that he instead implemented a quasi-experimentQuasi-experiment
A quasi-experiment is an empirical study used to estimate the causal impact of an intervention on its target population. Quasi-experimental research designs share many similarities with the traditional experimental design or randomized controlled trial, but they specifically lack the element of...
al design of matched pairs regarding the distribution of subjects within the experimental and control groups. Gresham and MacMillar (1998) also state a lack of a true representation of autism in that the subjects were neither randomly sampled from the cumulative autistic population nor were they randomly assigned to treatment groups. The internal validity
Internal validity
Internal validity is the validity of inferences in scientific studies, usually based on experiments as experimental validity.- Details :...
of the study was also called into question due to the possibility of skewed data resulting from three influential threats. Instrumentation, changes or variations in measurement of procedures over time, was argued to have been altered in both the pre-test and post-test conditions which were confounded by a differentiation in ascertaining cognitive abilities and intelligence of the subjects. The pre-test utilized four measures of cognitive ability and mental development. Five of the subjects' intelligence was determined through a parent-reported measure of adaptive behavior. All of the subjects were post-tested three years later using five other measures of intelligence and cognitive ability. Long-term follow-up was assessed with three measurements of (1) intelligence, (2) nonverbal reasoning, and (3) receptive language. The original three measurements during the testing phase were determined by (1) IQ score, (2) class placement, and (3) promotion/retention. External validity was called into question concerning sample characteristics. Lovaas' (1987) criteria for acceptance into the program required a psychological mental age greater than 11 months and a chronological age less than 46 months in the case of echolalic
Echolalia
Echolalia is the automatic repetition of vocalizations made by another person. It is closely related to echopraxia, the automatic repetition of movements made by another person....
children. Schopler et al. (1989) purport that if both the intellectual and echolalia criteria were rigidly adhered to at the North Carolina institute, approximately 57% of the referrals would have been excluded from the program.
Other criticisms include a failure to operationally define the use of the term 'reinforcement' for compliance, the use of a Pro-rated Mental Age, and the statistical regression of the child's IQ over time. Boyd (1998) addressed the potential impact of a disproportionate sex ratio
Sex ratio
Sex ratio is the ratio of males to females in a population. The primary sex ratio is the ratio at the time of conception, secondary sex ratio is the ratio at time of birth, and tertiary sex ratio is the ratio of mature organisms....
of females to males on the control group's mean IQ score. Females with autism typically display slightly lower levels of functioning in comparison to their male counterparts.
In a rejoinder to Boyd's (1998) article that cited an unequal sex ratio as a source of error, Lovaas (1998) listed three reasons as to why the disporportionate ratio's influence on the data was negligible. The autistic population at the time had a ratio of 4:1. Lovaas (1998) argued that the ratios for the experimental group, control group 1, and control group 2 of 16:3, 11:8, and 16:5, respectively, were in fact near the expected ratio scale of the general population with the exception of control group 1. The second argument lay in the studies Boyd (1998) referenced in regards to low intellectual performance in females diagnosed with autism. One of the studies admitted to having a female subject with Rett disorder, a condition that showed little responsiveness to intensive early behavioral intervention. Lovaas (1998) concluded by proposing that males may more readily meet diagnostic criteria for autism because of certain salient characteristics inherent in the sex while the subtleties in their female counterparts may be overlooked.