6.25 Monkey calls. The usual way to study the brain's re sponse to souiads is to have subjects listen to "pure tones."

The respoiase to recognizable sounds may differ. To compare re sponses, researchers anesthetized macaque monkeys. They fed pure tones and also monkey calls directly to their brains by in serting electrodes. Response to the stimulus was measured by the firing rate (electrical spikes per second) of neurons in var- T ious areas of the brain. Table 6.1 contains the responses for 37 neurons."

(a) One important finding is that responses to monkey calls are generally stronger than responses to pure tones. For how many of the 37 neurons is this true?

(b) We might expect some neurons to have strong responses to any stimulus and others to have consistently weak responses.

There would then be a strong relationship between tone re sponse and call response. Make a scatterplot of moiakey call resporise against pure tone response (explanatory variable). Find the correlation r between tone and call responses. How strong is the linear relationship?