Table 1 Analytical dimensions for the review

A. Year of publication

B. Research design

 1. Descriptive

 2. Experimental

C. Sample size

D. Subsample size (studies with two or more experimental conditions)

E. Sample/subsample type. Based on sample/subsample sizes.

 1. Case study: one subject

 2. Intensive: up to 30 subjects

 3. Extensive: more than 30 subjects

F. Temporality

 1. Cross-sectional

 2. Cross-sequential

 3. Longitudinal

G. Age range of subjects (in months)

H. Stimuli

 1. Two-dimensional

  i. Drawings and images

  ii. Abstract patterns

  iii. Videos

 2. Three-dimensional

  i. Objects: material entities that have not been built to fulfil a particular purpose but can be easily recognised by members of a community (e.g., a piece of mass, geometric shapes of various materials)

  ii. Artefacts: material entities constructed by a certain technique to fulfil a culturally determined canonical purpose (e.g., a spoon or a ballpoint pen).

  iii. Object, artefact and living beings replicas: material entities (usually small) that exactly reproduce the characteristics of an object/artefact or living being (e.g., a toy horse, a toy spoon).

  iv. Non-objects: material entities that resemble an object or artefact but would not be accepted as such by members of a community (e.g., stimuli constructed by experimenters manipulating different dimensions of materiality).

 3. Language

  4. Sounds and music

I. Data analysis

 1. Quantitative

 2. Qualitative

 3. Mixed

J. Age of development of categorical representations (in months)