Children's ability to recognize emotional expressions from faces and bodies develops during childhood. However, the low-level features that support accurate body emotion recognition during development have not been well characterized. This is in marked contrast to facial emotion recognition, which is known to depend upon specific spatial frequency and orientation sub-bands during adulthood, biases that develop during childhood. Here, we examined whether children's reliance on vertical vs. horizontal orientation energy for recognizing emotional expressions in static images of bodies changed during middle childhood (5 to 10 years old). We found that while children of all ages had an adult-like bias favoring vertical orientation energy, this effect was larger at younger ages. We conclude that in terms of information use, a key feature of the development of emotion recognition is improved performance with sub-optimal features for recognition--that is, learning to use less diagnostic features of the image is a slower process than learning to use more useful features.