Personality & Emotion

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Personality & Emotion
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Chao sleeping due to a high Sleepiness value.
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Some content to this article is speculative. Be warned.

Pesonality and Emotions are two features that determine the different ways that Chao behaves.


Personalities are features of Chao, displayed at the Health Center in the Chao Doctor's medical chart, which control some of a Chao's interactions and behavior in the Gardens. Personalities are a source of much mystery in current Chao Research, in how they effect a Chao's Actions, how and if they are determined genetically, and how they may effect a Chao's Face.

While the medical chart at the Doctor's office will only display one personality at a time, the same Chao over several visits, without even returning to the Garden, may display up to three different personalities, which are seemingly determined with equal likelihood. A Chao may have zero, one, two, or three total personalities that it may cycle through. The set of personalities a Chao may display at the Doctor's can be called a "personality profile" to differentiate it from the individual personality types it goes through.

The 13 personality sliders can be found in the table below.

Personality Constraints
(Min - Max)
Normal - Curious -100 to 100
Crybaby - Energetic -100 to 100
Naive - Normal -100 to 100
Normal - Big Eater -100 to 100
Normal - Carefree -100 to 100
Kindness -100 to 100
Solitude -100 to 100
Vitality -100 to 100
Regain -100 to 100
Skillful -100 to 100
Charm -100 to 100
Chatty -100 to 100
Fickle -100 to 100

Personalities which a Chao may display are determined through the above personality sliders. Since the characteristic names are only known through the game's debug menu, some of the names are rather non-descriptive, such as a "Charm" value, while others are quite clear on their function, such as the Crybaby-Energetic value. A Chao will have a certain personality if it has a slider value magnitude greater than 54. For example, if a Chao's value for the Crybaby-Energetic personality slider is <-54 it will display a Cry baby personality, while if it is >54 it will display an Energetic personality. Any value between -54 and 54 will not show either personality.

Effects on Behavior

A Chao's personalities (or rather, their personality slider values) affect its behavior in the Gardens. Most notably are the Big eater and Cry baby personalities, which are well known for their effects on Chao behavior. A Big eater Chao will eat in a ravenous way, the way which starving Chao eat, even while full. A Cry baby Chao cries for a longer period of time. While the Chao appears sad, this crying does not reduce the Chao's Happiness.

Broadly speaking, personalities cause various changes to a Chao's Emotion, or feelings, which are certain values that promote Chao into performing certain actions. For example, a Cry baby personality causes the Chao's "Urge to Cry" value to increase more quickly than other Chao, causing the Cry baby to cry more often if abused or hurt. A more subtle example is in the Solitude personality slider effecting a Chao's Loneliness emotion, which promotes a Chao into looking for the player's attention, by either nuzzling up to them or greeting them.


Substantial further testing is needed before any conclusive statements can be made on the inheritance of personality profiles on Chao. When breeding two homozygous Chao, both purchased from the Black Market, and who both only display one personality exclusively at the Doctors, their resulting children had one, two, or three personalities, including personality types which would not have been present as alleles in the parents. However, certain personality profiles seemingly occurred with unexpectedly great frequency. For example, breeding a purely Naive and purely Crybaby Chao resulted in repeat occurrences of child Chao which had a personality profile of Curious, Naive, and Carefree, and those which had personality profiles of Big Eater and Naive.

Personality and Face Relationships

A Chao's personality is seemingly related to values which also determine its initial face, as in its eyes and mouth. For example, a Chao which displays Curious, Naive, and Carefree personalities will have normal eyes, and a toothy grin. However, face and personality determination are seemingly related to several hidden values- a Chao may have the same normal eyes and toothy grin but display different personality combinations, such as being exclusively Naive. Additionally, the same personality profile may have different associated faces, where a Chao which is exclusively Naive may have normal eyes and a V-mouth, and another exclusively Naive Chao may have normal eyes and a normal mouth.

Since these relationships are non-injective and non-surjective, there are likely more hidden values involved, likely the exact personality slider values.


Emotions are the various values that influence a Chao's actions in the garden. These emotions are found in SA2B.

Emotion Constraints
(Min - Max)
Joy 0 - 200 Joy increases when a chao nuzzles against your character. This is achieved through a high character bond, and a high Lonely value.
After a certain level of Joy is reached, the chao will begin to jump around and cheer in an effort to get your attention.
The value slowly decreases during this time, until the behaviour ends.
Anger 0 - 200 Anger increases upon abuse/taking away food. Anger only affects dark chao, by causing them to stomp their feet and throw a tantrum.
High anger and dislike of a character may cause a dark chao to attack the player. Each attack landed decreases Anger by 10.
The value slowly decreases over time, until the behaviour ends.
Urge to Cry 0 - 200 Urge to cry is increased through abuse/taking away food. At high values, the chao will begin to cry.
The value slowly decreases over time, until the behaviour ends.
Fear 0 - 200 Fear is increased through abuse. The chao will cower and make a shivering noise to show it has been mistreated.
A high fear value, plus a high character fear value will result in the chao running away from the player in terror.
The value slowly decreases over time, until the behaviour ends.
Surprise 0 - 200 Surprise is increased through abuse, and decreases over time.
It is currently unknown what behaviour is tied to this value.
Relax 0 - 200 Relax increases when a chao is pet or picked up.
It is used to calculate how long a chao will stay still after being interacted with.
Total 0 - 200 Unused value of unknown purpose.
Sleepiness 0 - 10000 Sleepiness naturally increases over time, and with feeding. A high sleepiness value will make a chao fall asleep.
Sleepiness decreases while a chao sleeps.
Tiredness 0 - 10000 This value increases while a chao is asleep. It causes a chao to act groggy if its sleep is disturbed by the player.
This value significantly decreases near the end of a chao’s nap.
Hungry 0 - 10000 Hunger decides how hungry your chao is.
At 0 hunger, your chao has a high chance of throwing/leaving food.
Desire to mate 0 - 10000 This value will cause your chao to go into mating season. The value increases naturally after your chao evolves into an adult.
Feeding your chao a Heart Fruit will set this value to its max of 10000.
Boredom 0 - 10000 Boredom makes your chao more likely to play with garden/race toys and perform animal/classroom behaviours.
It increases naturally over time, and significantly decreases when performing actions.
Lonely 0 - 10000 This value, alongside a high character bond and a high character distance value makes your chao more likely to seek interaction from the player.
Dark-aligned chao will give a thumbs-up, while Hero-aligned chao will bow.
Chao may also follow you and nuzzle against you.
Tire 0 - 10000 This value increases naturally over time, and will cause your chao to sit down.
If sleepiness is high enough while a chao is sitting, it can fall asleep sitting up.
Stress 0 - 10000 This value causes a chao to always die, even with maximum happiness.
The value goes unused in the final game, and there is no way to increase it naturally.
Nourish 0 - 10000 Nourish is set before an egg hatches, and will begin to decrease after the chao is born.
Currently, it is unknown what this value is supposed to do.
Conditn (Condition) 0 - 10000 Condition seems to prevent Sickness Animations. As Nourish naturally decreases, Condition will slowly begin to increase.
Curiously, it only seems to increase when the chao is sitting still, and not when the chao is swimming or walking around.
Condition will then rapidly decrease as Nourish gradually moves towards 0.
Energy 0 - 10000 Energy makes your chao want to swim, even if they are unable to. As such, they will target the water continuously until the value decreases over time.
Energy will also make your chao move around more in the garden.
This value has a higher priority over Boredom.


Although not an 'emotion' by description, they are included under the emotion struct and function similarly.

Illness Constraints
(Min - Max)
Cough -100 to 100 At negative values, chao coughs occasionally.
Goes up to 100 once cured at doctors.
Cold -100 to 100 At negative values, chao will sneeze occasionally.
Goes up to 100 once cured at doctors.
Rash -100 to 100 At negative values, chao will scratch at itself.
Goes up to 100 once cured at doctors.
Running Nose -100 to 100 At negative values, chao will stand with a displeased face.
This sickness goes unused in the final game.
As such, the animation is unfinished and the Doctor's dialogue has some translation issues.
Goes up to 100 once cured at doctors.
Hiccups -100 to 100 At negative values, chao hiccups occasionally.
Goes up to 100 once cured at doctors.
Stomach Ache -100 to 100 At negative values, chao experiences a stomach ache.
Goes up to 100 once cured at doctors.

Sonic Adventure (Dreamcast)

The Dreamcast version of the game also has personality values, but you cannot see these in text form. Instead, they determine your Chao's face. Chao have three personalities, decided upon birth. Kindness, Aggressiveness and Curiosity. These values range from -100 to 100.

If the value is lower than -35, it is classed as *low*. Over 34 is classed as *high*, and anything in-between is *medium*.

The combination of these three personalities will result in specific faces. These are all documented at the Chao Gallery.