Cat intelligence
The brain of the domesticated cat is about long, and weighs . If a typical cat is taken to be long with a weight of , then the brain would be at 0.91% of its total body mass, compared to 2.33% of total body mass in the average human. Within the encephalization quotient proposed by Jerison in 1973, values above 1 are classified big brained, while values lower than 1 are small brained. The domestic cat is attributed a value of between 1–1.71 relative to human value that is 7.44–7.8. The largest brains in the Felidae family are those of the tigers in Java and Bali, of which the largest relative brain size within the "panthera" is the "tigris". It is debated whether there exists a causal relationship between brain size and intelligence in vertebrates. Correlations have been shown between these factors in a number of experiments. However, correlation does not imply causation. Most experiments involving the relevance of brain size to intelligence hinge on the assumption that complex behavior requires a complex (and therefore intelligent) brain; however, this connection has not been consistently demonstrated.
Fetal EEG
The youngest fetus that Borkowski and Bernstine studied was between 43 and 45 days post-conception – only 16mm long. At 45 days after conception, the brain is bent forward and is almost as large as the entire body of the fetus, allowing for these deep recordings. The 45-day old fetus’s electrical signals resembled the “discontinuous” patterns observed in healthy newborns, premature infants, and fetuses in the last trimester of pregnancy. The doctors also observed patterns that resembled “sleep spindles” in adults. The scientists continued recording until they consistently observed patterns of brain death, since the fetuses could not survive outside the uterus.