Bayley Scales of Infant and Toddler Development | Fourth Edition

Bayley-4 UK
Bayley-4 UK is the most comprehensive assessment tool for determining developmental delays in children. Sign-up here to stay updated on the Bayley-4 UK. 
Enjoy a special discount on our complete kit options for the Bayley-4 UK ! Use code SUMMERUK10 at checkout to receive 10% off. This limited-time offer is valid from 17th June 2024 to 30th August 2024. Don't miss out!
View all tests and materials
Prices include VAT where applicable
Bayley-4 US Technical Manual (Print)
A102001600044 Qualification Level B




Publication date:
Age range:
16 days to 42 months
Subtest level scaled scores, domain level composite scores, percentile ranks, confidence intervals, developmental age equivalents, and growth scale values 
Qualification level:
Completion time:
30 to 70 minutes (depending upon age of child)
Paper-and-pencil; Q-global
Scoring options:
Q-global (web-based); Manual


Unboxing the Bayley-4 UK kit 

Watch our unboxing video and see what is included in the Bayley-4 UK complete kit.

Find the video here

Product Details

Professionals have relied on the Bayley Scales of Infant and Toddler Development™ for more than 50 years to identify potential delays in children and get interventions in place early on. 


  • Use caregiver responses to support the scoring of certain items.
  • Determine the need for further in-depth assessment.
  • Administer one or more domain subtests individually.
  • Save significant time through shortened adaptive behaviour content from Vineland 3.


The new version of the Bayley Scales of Infant and Toddler Development Fourth Edition features:

  • The digital delivery option via Q-global combines the record form and administration manual, which allows greater flexibility, ease of use, and improved accuracy.
  • Content updates are made based on research and user feedback.
  • Updated normative data and clinical studies.

Five developmental domains





Bayley-4 UK Training Offerings

Visit our Bayley-4 UK training page to find the training that suits your needs including our scheduled 2-day online workshop. Upcoming dates and booking information can be found here.

Our interactive two-day online workshop will teach course participants to administer, score and interpret the Bayley-4, using videos of young children with and without clinical presentations. Participants will learn how to administer and score the Cognitive, Language and Motor scales.

Unsure about which Bayley-4 UK training is best for you? Download our Training Offering & Decision Tree PDF to compare the range of options available. 

To purchase, select the training tile above this tab to complete your order online. 





Kits, components, and pricing

If I have a Bayley-III UK kit, can I upgrade to Bayley-4 UK? If so, what are the options?

Materials are available to purchase separately; however, it is more expensive to upgrade this way than to purchase a new kit, i.e. the items required to upgrade would be:

  • Bayley-4 UK Administration Manual (paper or digital)
  • Bayley-4 UK Technical Manual (paper or digital)
  • Bayley-4 UK Stimulus Book (paper)
  • New Manipulatives (small set of discs (3); cat puzzle; memory cards; ducks; coins bank; large discs (6); small car)
  • For manual administration and scoring:
    • Bayley-4 UK Record Forms and Response Booklets (pkg of 25 of each)
    • Social-Emotional and Adaptive Behaviour Questionnaires (pkg 25)
    • Caregiver Report (pkg of 25)
  • For digital administration and scoring:
    • Q-global: Cognitive, Language and Motor administration, scoring & report and Response Booklets
    • Q-global: Social-Emotional & Adaptive Behaviour administration, scoring and report

What is the difference between Bayley-4 UK Q global Scoring Subscriptions and Bayley-4 UK Q global Reports?

The Scoring Subscriptions provide a digital scoring option for paper-based administration. They allow manual entry of raw data to generate scores and reports.

The Cognitive, Language and Motor Administration, Scoring and Report is used for the on-screen administration of these domains, and is a digital version of the Record Form. This is for the Examiner to use and complete.

The Social-Emotional and Adaptive Behaviour Administration, Scoring and Report is a digital equivalent of the Social-Emotional & Adaptive Behaviour Questionnaire. This is a caregiver questionnaire that can be emailed to the caregiver with a secure link to complete or can be completed within your office on an internet-enabled device.

I recently purchased the Bayley-III UK kit, can I return it and purchase the Bayley-4 UK instead?

Pearson provides product credit on qualifying returns. Find out more at here.

When will I receive my order?

We anticipate that Bayley-4 UK will ship Summer 2023.


How do the integrated caregiver questions contribute to the scoring of an item?

For certain questions a caregiver response is possible for scoring the item, see the example below:

Ask the caregiver, 'When you say the name of a familiar object, does [insert child's name] look at the object you named often, not often, or not at all?'

2 points, Often
1 point, Not often
0 points, Not at all

For those items for which a structured/observation score and a Caregiver Question score can be obtained, is it recommended to ask the caregiver question in every instance where mastery (i.e. a score of 2) is not assigned based on the structured item administration or observation? 

The Caregiver Question should not be used in every item where it is an option or where a score of '2' is not assigned. The intent of the caregiver questions is not to optimise scores as much as possible. Rather, they are to be used when a response is ambiguous, the child is not cooperative, or if the behaviour may have a greater likelihood of occurring in familiar surroundings. Frequent discrepancies between what is observed during testing and the caregiver question responses raises questions regarding the validity of Caregiver Question scores, and clinical judgement should guide interpretation.  

At what age is prematurity considered for Bayley-4 UK?

Prematurity is considered 36 weeks 6 days or less gestation. This is what is meant by '36 weeks or less gestation' on page 27 of the Bayley-4 UK administration manual.

Digital Administration and Scoring

Can you log in to the digital scoring and save the score report so that another discipline can enter and score their section for the same child?

This is possible and depends on how the account is set up. Some Q-global users intentionally set up their accounts so that all their team members can view their examinees as a group (rather than just the ones they have entered). Of course, an account can also be set up so that users can only see their own examinees. This is a choice made when the account is set up.

If an account is set up so that it is in the same hierarchy as other accounts, then the examinee record can be moved from one account to another for other disciplines to enter and score their section. Examinee records cannot be moved to an account within a separate entity / hierarchy.

Is there any data on differences between administration using paper vs. digital formats?

The digital administration of Bayley-4 UK is a digital record form, the child does not interact with the administration device (e.g. tablet/laptop), the administration guidelines between paper and digital are the same.

As part of the Bayley-4 UK validation we conducted a study comparing performance on Bayley-III UK (paper scoring) and Bayley-4 UK (digital scoring). The data indicates that the children's performance on the two tests are similar (no significant difference).

How do I administer Bayley-4 UK digitally?

The digital administration uses Q-global and combines the record form and administration manual for more streamlined administration. It is optimised for the screen-size of a tablet (e.g. iPad) or larger. Although it will work on a smart phone it will not be a good user experience. Q-global can be used on any device that has internet. You cannot use Q-global without internet access.

The Social-Emotional and Adaptive Behaviour Questionnaires can be administered remotely via a secure email link.

Will the programme be able to let the examiner know when you should stop correcting age for premature babies?

It is recommended to adjust for prematurity up to 24 chronological months, however, the platform will allow you to adjust beyond this age. There is on-screen text advising the recommended ages for adjusting.

Can you pull up the original evaluation and add to it for re-evaluations?

Growth Scale Values are included in Bayley-4 UK. These are useful for re-evaluation purposes and are available for both paper and digital administration.

For paper administration statistical significance is also available to evaluate change in Growth Score Values between two administrations.

What happens if your internet connection drops during administration?
Information is continually backed up in Q-global, if so a connection drops during administration then any data entered will have been saved. Once you're able to reconnect, the session will continue from where you left off.
Is offline administration available?
Offline administration is not available currently. The back-up option is to use paper administration, and enter the scores manually; a subscription version of Bayley-4 UK on Q-global is available to facilitate this.
Can Bayley-4 UK be administered remotely via telepractice?
The Social-Emotional and Adaptive Behaviour Questionnaire can be administered remotely. Guidance to support telepractice administration of Bayley-4 UK  is available here.


How are growth scale values reported?

Growth scale values (GSVs) provide a score metric that does not involve age-based comparisons. Their purpose is for tracking performance across repeated test administrations. If a raw score increases upon a repeat administration, the GSV also increases.

The GSVs have a mean of 500 and a SD of 25. Because of their construction, GSVs cannot be meaningfully compared between subtests or subdomains. GSVs enable the measurement of an individual child's progress or improvement in an absolute sense. Although the normative scaled scores provide information about a child relative to their peers at a given time and may show little change over time, the GSV can provide an ability to estimate independent of one's peers and can track growth over time.


How do you access training with new kit purchases?

If you purchased our Bayley-4 UK Complete Kit (Print) / On-demand Training Combo or Bayley-4 UK Complete Kit (Digital) / On-demand Training, please refer to the welcome letter provided with your kit.

If you have not purchased one of our bundled options (kit + training), you can view training options under the training tab on the Bayley-4 UK webpage.

What happens after I place my order for the Bayley-4 UK In Person Training Course? 

  • A Pearson consultant will contact you within 2-3 business days of order placement to coordinate your training, this includes confirming your choice of preferred dates and delegate numbers.  
  • Your Pearson consultant will then liaise with our Course Leader, Dr Betty Hutchon to confirm availability for your preferred date/s.  

  • On confirmation that your preferred date is available (and subject to you having ordered and paid online or submitted a purchase order), you’ll receive a confirmation email which will provide guidance on the next steps, this will include an excel template that we require to be populated with the first name, last name and email address of all delegates.  

  • The course organisers details and information will be passed on to our Course Leader, Dr Hutchon who will contact the organiser directly in advance of the training.  

  • Approximately 2 weeks before your scheduled training date, our customer support team will arrange for any course materials (record forms) to be delivered to your location. It's important that you look out for these as they will be used during the training. Please contact us at least 5 days before your course start date should you not receive these.  

  • Printed handouts are not provided as part of our training. Our Course Leader will email any such material to the course organiser only. 

  • Certificates of attendance/digital badges will be issued automatically via Credly following attendance at the training. This will be issued to the delegates you listed during either via the online ordering process (if you ordered online) or via the excel template the Pearson consultant asked you to complete. A post-course feedback request link will also be sent to this list of delegates. 



The following training events are available for Bayley-4 

Introduction to Bayley-4 UK Webinar (Recording)
Presenter(s): Melinda Cooper

Bayley-4 UK is the most comprehensive assessment tool for determining developmental delays in children. In this presentation Melinda Cooper, Senior Product Manager, Occupational Therapy will cover:

  • An introduction to the Bayley-4 UK
  • Revision goals
  • What has changed from Bayley-III
  • New administration and scoring features
  • What else is coming soon

Evaluating Language Skills and Early Signs of ASD with the Bayley-4  Webinar (Recording)
Presenter(s): Anise Flowers & Shannon Wang

One of the diagnostic areas that characterise Autism Spectrum Disorder is impaired communication. The Bayley-4 can be used to evaluate the early communication skills of children aged 16 days to 42 months. The presenters will describe Bayley-4's flexible administration process, which includes series items, related items, caregiver questions, and digital administration.

Recorded: Tuesday, 16th March, 2021

Considerations in Conducting Developmental Assessments Using the Bayley-4 Webinar (Recording)
Presenter(s): Gloria Maccow, Ph.D

Using multiple methods and collecting information from multiple sources are considered best practices when assessing infants and toddlers to identify developmental delays. When the assessment includes standardised tests, it is important to consider how the early development and behaviours of young children can impact their performance, especially on structured tasks.

Recorded: Thursday, 22nd October, 2020