Matching activities are popular for toddlers. For instance, the Lovevery play kit for months 19-21 has a match pictures activity (e.g. matching the image of a butterfly to another image of a butterfly). The kit for months 22-24 has an activity to match animal figures to pictures of animals (e.g., a cow figure to a picture of a cow).1 But beyond that including an object shape recognition activity for toddlers might be helpful. For instance, matching a silhouette to a picture or an object can help practice object shape recognition.
In a 2019 study from Sweden, how well children recognized silhouettes at 20 months old was significantly correlated to their “language and cognitive abilities at 6-7 years even after controlling for toddler vocabulary size”. For instance, toddlers had to recognize the silhouette of a duck correctly as a duck and that the silhouette of a car is not a duck. This was measured by electrophysiological data. This was a longitudinal study, not an intervention study.2
So while there is more research to be done, the study shows that paying attention to shapes is important and silhouettes can help with that. You can create a shape recognition activity for toddlers yourself. For instance, you can extend a picture-to-picture or picture-to-object activity you already have by adding silhouette pictures. You could also use silhouettes to match pictures in a book or objects around the house. Pinterest also offers a lot of activities that are already down. They often are labeled “shadow match”, with other terms including “vector silhouettes”. Especially look for those where you (as an adult) would recognize what the object is by the shadow picture alone. For instance, this one has animals. The giraffe, elephant, and dromedary are easy to recognize just from the shadow image, while the rhino is not (that could be a hippo, too, as the horn is not clearly visible). Here are some more examples: an excavator, different leaves, wild animals (squirrel, bunny, bear, hedgehog, …), or farm animals.
References:
1 Lovevery (n.d.) The Play kits. https://lovevery.com/products/the-play-kits?gad_source=1&gclid=Cj0KCQjwiMmwBhDmARIsABeQ7xT2bgLJ6GUVXEy5KSN8nCvvgKOYoCvgHxw0NTWTF4hhVM7BuGOzhtQaAlmmEALw_wcB
2 Borgström, K., von Koss Thorkildsen, J., Sohlen, B., and Lindgren, M. (2019). Brain Measures of Toddlers’ Shape Recognition Predict Language and Cognitive Skills at 6–7 Years. Frontiers in Psychology, Vol. 10, Art. 1945. doi: 10.3389/fpsyg.2019.01945