Unpacking the IDS-2 with Dr Selma Ruiter (Q&A)

Anticipation is mounting for the forthcoming Intelligence and Development Scales – Second Edition (IDS-2) – a ground-breaking new assessment coming in September (and available to pre-order now). The IDS-2 allows the user to assess the ‘whole child’ through six cognitive and developmental domains (Intelligence, Executive Functions, Psychomotor skills, Social-emotional skills, Scholastic skills, and Motivation and Attitude) with one test kit. 

Whilst awaiting these brand-new kits fresh from the printer, we spoke with one of the authors of the Dutch version of the IDS-2, Dr Selma Ruiter, about the theoretical basis of the test, some of the key areas it measures, and the value it offers to psychologists today. 

While the IDS-2 has already seen incredible success in The Netherlands, Germany and Switzerland, the test will be new to the UK market when it launches next month. How would you describe the IDS-2?

The IDS-2 is an instrument with which the psychologist can perform an integrative diagnostic examination. The intelligence test is very extensive and forms the core of the instrument, however, the IDS-2 also offers the possibility of mapping general cognitive functioning, because not only intelligence but also executive functioning can be examined. An analogy we use for this is that of the engine and fuel: the engine (intelligence) cannot run without the fuel (executive function). 

The uniqueness of the IDS-2 is that both specific referral questions and very broad questions can be answered. The IDS-2 is like a doctor's kit for psychologists: in addition to intelligence and executive functioning , you can also use it to assess social-emotional functioning, gross and fine motor functioning and do an evaluation of academic skills in reading, writing and mathematics.

The IDS-2 is an instrument that is not only very broad in terms of content, but also in terms of the age range, which is 5 to 20 years and 11 months.


The IDS-2 is like a doctor's kit for psychologists: in addition to intelligence and executive functioning , you can also use it to assess social-emotional functioning, gross and fine motor functioning and do an evaluation of academic skills in reading, writing and mathematics.

Does the IDS-2 have a strong theoretical base? What is the research evidence to support it?

The IDS-2 is intended to represent the full CHC model. This CHC model is a theoretical model that is strongly empirically-based. All major and modern IQ tests worldwide are based on this model, which is a foundation of the construct for ‘Intelligence’. Tests based on this model offer the user a huge range of insight.

The IDS-2 can be used to build a cognitive profile of the child or adolescent through assessing both intelligence and executive functioning. What sort of questions does this help to answer?

As an example, children with learning difficulties may have a high IQ, so they score well on an intelligence test, but have a lot of difficulty with school learning, because they have, for instance, difficulty concentrating, difficulty switching between assignments or strategies, difficulty focusing attention for a long time, or difficulty with planning and memory. In assessing learning problems and obtaining information to set up guidance or treatment, it is important to have a good picture of general cognitive functioning.

And how does the IDS-2 measure psychomotor skills? Why is it important to be able to assess these?

Psychomotor skills affect a person's general functioning and also specifically a child's performance in education. A slow learner may not actually be slow to process information, but may have difficulty handling a pen or pencil. In addition, some learning disabilities go hand in hand with motor coordination disorders – a low score on a part of the motor functioning can be a signal for problems with a certain subject at school. Motor coordination problems are related to, for example, maths problems.

The IDS-2 also measures social-emotional skills – what information can it provide and why is it helpful?

The IDS-2 can accurately assess a child's ability to recognise emotions, regulate them, and deal with social situations. The connection between the social-emotional functioning of a child and, for example, performance at school or specific behavioural problems, has often been proven. Information in this area can provide insight into the cause of specific problems concerning the daily functioning of a child, or specifically the functioning of a child at school. Problems in this area can also be the cause of secondary problems. It is therefore important to treat possible problems on a social-emotional level or to take this into account when treating learning problems.

How does the IDS-2 inform next steps and possible interventions?

The IDS-2 first gives a snapshot of the performance level of a person at this moment in time, and then to determine the strengths and weaknesses of a child. These strengths and weaknesses are the most important part of building a treatment plan. Predicting future functioning is not a primary goal of the test, but rather obtaining an accurate and up-to-date picture of the functioning of a child at this moment – this then informs the areas where a child can use help and support to improve future functioning and prevent the chance of developmental delays or problems becoming worse.

What has the response to the IDS-2 been like from psychologists in The Netherlands?

Extremely positive. The two striking features of the IDS-2, in particular its extended age range and extensive content, distinguish the IDS-2 from all other important instruments we have at our disposal in The Netherlands.

More on the IDS-2

Coming to the UK September 2021, the IDS-2 is a global cognitive assessment for use with ages 5 to 20 years and 11 months. Find out more about the IDS-2, or pre-order your kit today by visiting our website. If you have a question about the IDS-2, please visit our FAQs page or contact us to discuss.


About Selma Ruiter

Dr Selma Ruiter completed her training in Orthopedagogics at the University of Groningen in 1998 with a combined practical and research internship at University College London. She is an expert in the development and application of intelligence tests and is very engaged in research, education and practice. She authored the Dutch version of the IDS-2 and other tests such as the Dutch version of the WISC-V as well as the Bayley-III-NL SNA and the SON-R 2-8, the WISC-V-NL). She is also a teacher of post-master's programs about psychodiagnostics in general and development and intelligence research. She provides training on behalf of training institutes and test publishers in the application and interpretation of the most important development and intelligence tests in the Netherlands. Finally, Selma, is responsible for conducting and interpreting psychodiagnostic research in practice at the Children's Academy Groningen, which she co-founded in 2012.