Make sure you have a solid grasp of the Pearson General Alternative Text Guidelines and Understanding Image Types before reviewing this Science authoring section. You may also want to review the Math authoring section for guidance on writing alt text for numbers, equations, molecular formulae, and units.
Quick Reminders
- Word choice/terminology: Use the terminology and reading level from the main text.
- The alt text should not give away the answer or provide an unfair advantage to students using assistive technology.
- Image types (e.g., photo, drawing): Do not identify the image type in the alt text unless it’s important for understanding the information in the image.
- The importance of the image type depends on context (i.e., image purpose). For example, if a photo is meant to demonstrate the effects of using certain camera filters, then it should be identified as a “photo.”
- Always identify the following image types at the beginning of the alt text: graphs, line graphs, bar graphs, pie charts, flow charts, tree diagrams, box plots, stem and leaf plots, and micrographs.
- Assessment images: Provide enough information for the student to answer the associated questions. But do not give away the answer. Try to provide an equivalent level of challenge without unnecessarily increasing the cognitive load. For example, the alt text can include the image details related to the correct answer and two distractors.
- Static images used as links to open videos, simulations, or media: The alt text can simply read “Select to launch X” or “Launch X”.
- Tables: Whenever possible, tables should be marked up in HTML. However, there are times when tables must be rendered as images. When necessary, provide alt text and when applicable, long descriptions for the table images.
- Numbers/Symbols/Equations: Refer to the Math section for specific guidance on how to write alt text for these items.
- Superscript and Subscripts
- Denote subscripts and superscripts only when the user needs this information to understand the meaning of the equation.
- When a title comes up for re-edition, STEM elements which include subscripts or superscripts, it is not required to edit previously written descriptions. It is acceptable to maintain the alternative text previously written and follow the “refreshed” guidelines for new alternative text.
- The abbreviation “sub” and “super” are highly recommended for two main reasons:
- Fosters brevity.
- Reduces the alt text character count which is helpful when trying to stay under 255 characters.
In the following examples, subscripts and superscripts are NOT needed to understand the content:
| Math Expression | Alt Text |
|---|---|
| H2O | H 2 O |
| CH4 | C H 4 |
| x5 | x to the fifth power |
| f-1(x) | f inverse of x |
| d2y / dx2 | d 2 y over d x squared |
| 1s22s22p63s23p2 | 1 s 2, 2 s 2, 2 p 6, 3 s 2, 3 p 2 |
In the following examples, subscripts and superscripts are NEEDED to avoid ambiguity:
| Math Expression | Alt Text |
|---|---|
| P1V1=P2V2 | P sub 1 V sub 1 = P sub 2 V sub 2 |
| z1 = r1(cos θ1 + i sin θ1) | z sub 1 equals r sub 1 left paren cosine theta sub 1 plus i sine theta sub 1 right paren |
| anpn + an-1pn-1 + . . . | a sub n p to the n power plus a sub n minus 1 baseline p to the n minus 1 power plus ellipsis |
 | Super 12 sub 6 C |
Platform Authoring Information
Mastering
- Mastering has a title field and one alt text field.
- The title field can be used to display hover text, which is capped at about 255 characters including spaces. Hover text should be a short description of the image but should never replace the alt text.
- The alt text field is mandatory and capped at about 1024 characters including spaces.
- The alt text should never repeat the image title verbatim. When this happens, screen reader users may hear the information twice, resulting in a poor user experience.
- The title field is an optional field. Check with the Content Producer or Manager to determine if it will be used.
- Only plain text is allowed. The title and alt text fields do not support formatting such as bullets, bold, italics, sub/superscripts, and tables.
- When multiple figures are combined into one image, each figure must be addressed more succinctly so that all figures can be described within the character limit. If adequate alt text cannot be provided in this way, consider splitting the figures into separate image files.
- For answer types that include images, alt text must be written for each image.
- Provide alt text for images that are answer choices in multiple choice or multiple select answer types.
- The following answer types support background images: sorting, ranking, labeling, graphing, vector/moment, and input on diagram. In addition, hotspots can be added within the vector/moment tool, so for these, a brief description identifying the point in the diagram should be added.
- In the labeling answer type, alt text should be included for the background image, any image labels, and the targets. The target alt text must describe the context of the target in relation to the background image so that a vision-impaired student knows what is being asked for in that target. However, the target alt text should not give away the answer.
- For tables in Mastering, header cells should be designated accordingly by changing the Cell Type to Header Cell.
eText 2
- eText2 files contain both an alt text and long description fields.
- Alt text is sometimes referred to as the “short description.” It should be no more than 255 characters including spaces (approximately 30 words or less), and it should summarize the meaning or purpose of the image. Alt text must be in plain text and should NOT be written in HTML. It cannot support superscript characters, bulleted lists, or tables.
- If an image cannot be fully explained in the alt text, an additional “long description” is required.
- Long descriptions can be any length.
- Long descriptions can support structured text (e.g., bulleted lists, headings, and tables) and MUST be coded in HTML.
- When a long description is required, the image still needs alt text (short description). In such cases, the alt text should identify the image well enough for the user to decide whether to access the long description. For instance, “A flow chart” is not sufficient for alt text. “A flow chart of the manufacturing process” is better.
- If multiple figures are combined into one image file, the corresponding alt text for each figure/part is combined into one description. Most likely this description will have a short and long text alternative.
- Alfresco does not allow decorative or redundant images to be given a null alt attribute (i.e., skipped by the screen reader). So, we must provide alt text for all images.
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Guidance by Discipline or Topic
This section provides example alt text for representative images from the following disciplines/topics. Similar image types can be used for different disciplines, and you are encouraged to review all examples under each sub-section. For instance, the examples in the Biology and Chemistry sections might also apply to Anatomy and Physiology.
Dated: 2024-01-17