The various realms in the Pali suttas include psychological examples therefore obviously this is all that can be known. For example:
It is just within this fathom-long body, with its perception & intellect, that I declare that there is the world, the origination of
the world, the cessation of the world and the path of practice leading
to the cessation of the world. AN 4.45
And what is the origination of the world? Dependent on the eye & forms there arises eye-consciousness. The meeting of the three is
contact. From contact as a requisite condition comes feeling. From
feeling as a requisite condition comes craving. From craving as a
requisite condition comes clinging. From clinging as a requisite
condition comes becoming. From becoming as a requisite condition comes
birth. From birth as a requisite condition, then aging & death,
sorrow, lamentation, pain, distress, & despair come into play. This is
the origination of the world. SN 12.44
Follow not the vulgar way; live not in heedlessness; hold not false views; linger not long in worldly existence. Blind is the world; here
only a few possess insight. Only a few, like birds escaping from the
net, go to realms of bliss. Lokavagga
Intention, I tell you, is kamma. Intending, one does kamma by way of body, speech, & intellect. And what is the cause by which kamma comes
into play? Sense contact is the cause by which kamma comes into play. And
what is the diversity in kamma? There is kamma to be experienced in
hell (niraya), kamma to be experienced in the realm of animals (
tiracchānayoni), kamma to be experienced in the realm of the hungry
shades (pettivisaya), kamma to be experienced in the human world
(manussaloka), kamma to be experienced in the world of the devas
(devaloka). This is called the diversity in kamma. AN 6.63
I have seen, bhikkhus, the hell named ‘Contact’s Sixfold Base.’ There whatever form one sees with the eye is undesirable, never desirable;
unlovely, never lovely; disagreeable, never agreeable. Whatever sound
one hears with the ear … Whatever odour one smells with the nose …
Whatever taste one savours with the tongue … Whatever tactile object
one feels with the body … Whatever mental phenomenon one cognizes with
the mind is undesirable, never desirable; unlovely, never lovely;
disagreeable, never agreeable. SN 35.135
Here, Udayi, the bhikkhu secluded from sensual desires and thoughts of demerit abides in the first jhana: Overcoming thoughts and thought
processes and the mind in one point internally appeased, without
thoughts and thought processes abides in the second jhana. Again with
equanimity to joy and detachment, feeling pleasant with the body too,
abides in the third jhana. To this the noble ones say abiding in
pleasantness with equanimity. Udayi, this is the course of actions,
for realising the world of only pleasant feelings (ekantasukhassa
lokassa).MN 79
Bhikkhus, there are three kinds of persons found existing in the world. What three? (1) “Here, bhikkhus, some person generates
afflictive bodily activities, afflictive verbal activities, and
afflictive mental activities. In consequence, he reappears
(upapajjati) in an afflictive world. When he reappears in an
afflictive world, afflictive contacts touch him. Being touched by
afflictive contacts, he feels afflictive feelings, exclusively
painful, as in the case of hell-beings. (2) “Someone else generates
unafflictive bodily activities, unafflictive verbal activities, and
unafflictive mental activities. In consequence, he reappears in an
unafflictive world. When he reappears in an unafflictive world,
unafflictive contacts touch him. Being touched by unafflictive
contacts, he feels unafflictive feelings, exclusively pleasant, as in
the case of the gods of refulgent glory. (3) “Still another generates
bodily activities that are both afflictive and unafflictive, verbal
activities that are both afflictive and unafflictive, and mental
activities that are both afflictive and unafflictive. In consequence,
he reappears in a world that is both afflictive and unafflictive. When
he reappears in a world that is both afflictive and unafflictive, both
afflictive and unafflictive contacts touch him. Being touched by both
afflictive and unafflictive contacts, he feels both afflictive and
unafflictive feelings, mingled pleasure and pain, as in the case of
human beings, some devas, and some beings in the lower worlds. These,
bhikkhus, are the three kinds of persons found existing in the world.
AN 3.23
Sensual desire… ill-will (anger)… sloth & drowsiness… restlessness & anxiety… uncertainty is an obstacle, a hindrance that overwhelms the
mind and weakens wisdom… when a monk has not abandoned these five
obstacles… for him to understand what is for his own benefit, to
understand what is for the benefit of others, to understand what is
for the benefit of both, to realize a superior human (manussa) state
(dhammā), a truly noble distinction in knowledge & vision: that is
impossible. AN 5.51
Sooner, I say, would that blind turtle, coming to the surface once every hundred years, insert its neck into that yoke with a single hole
than the fool who has gone once to the nether world would regain the
human state. For what reason? Because here, bhikkhus, there is no
conduct guided by the Dhamma, no righteous conduct, no wholesome
activity, no meritorious activity. Here there prevails mutual
devouring, the devouring of the weak. For what reason? Because,
bhikkhus, they have not seen the Four Noble Truths. What four? The
noble truth of suffering … the noble truth of the way leading to the
cessation of suffering. SN 56.47
Bhikkhus, a god, a human or any other good state would not be evident from actions born of greed, hate and delusion. Yet, bhikkhus, from
actions born of greed, hate and delusion a hellish being, an animal
birth a ghostly birth or some other bad state would be evident. AN
6.39
Bhikkhus, these two bright principles protect the world. What are the two? Shame and fear of wrongdoing. If, bhikkhus, these two bright
principles did not protect the world, there would not be discerned
respect for mother or maternal aunt or maternal uncle’s wife or a
teacher’s wife or the wives of other honored persons, and the world
would have fallen into promiscuity, as with goats, sheep, chickens,
pigs, dogs, and jackals. But as these two bright principles protect
the world, there is discerned respect for mother… and the wives of
other honored persons. AN 2.9
Now on that occasion the wanderers of other persuasions had come together in a gathering and were sitting, discussing many kinds of
bestial (animal) topics, making a great noise and racket. AN 10.93
Beings (sattā) are few who, when they pass away from the animal realm (tiracchānayoniyā) are reborn (paccājāyanti) among humans
(manussesu)… those beings are more numerous are reborn in hell…. For
what reason? They have not realised the Four Noble Truths. SN 56.102
to 131
There are these four kinds of generation. What are the four? Egg-born generation, womb-born generation, moisture-born generation and
spontaneous generation. What is egg-born generation? There are these
beings born by breaking out of the shell of an egg; this is called
egg-born generation. What is womb-born generation? There are these
beings born by breaking out from the caul; this is called womb-born
generation. What is moisture-born generation? There are these beings
born in a rotten fish, in a rotten corpse, in rotten dough, in a
cesspit, or in a sewer; this is called moisture-born generation. What
is spontaneous generation? There are gods (devā) and denizens of hell
(nerayikā) and certain (ekacce ca) human beings (manussā) and some
(ekacce ca) destined to suffer (vinipāta); this is called spontaneous
generation. MN 12
