PHP Notice: Array to string conversion; Database Factories

I have a talent model which can have many educations which I want to populate using data factories. But populating the education section cause "Array to string conversion". From what I see, I am not giving an array to be converted into a string. Below are the Education's model, migration & factory

class Education extends Model
{
    protected $fillable = [
        'talent_id',
        'institution',
        'education_level',
        'other_education_level',
        'qualification_field',
        'start_date_month',
        'start_date_year',
        'end_date_month',
        'end_date_year',
    ];

    public function talent() {
        return $this->belongsTo(Talent::class);
    }
}

Schema::create('educations', function (Blueprint $table) {
    $table->bigIncrements('id');
    $table->unsignedBigInteger('talent_id')->index();
    $table->string('institution');
    $table->string('education_level');
    $table->string('other_education_level')->nullable();
    $table->string('qualification_field');
    $table->unsignedTinyInteger('start_date_month');
    $table->unsignedSmallInteger('start_date_year');
    $table->unsignedTinyInteger('end_date_month')->nullable();
    $table->unsignedSmallInteger('end_date_year')->nullable();
    $table->timestamps();
});

$factory->define(Education::class, function (Faker $faker) {
    return [
        'talent_id' => factory(\App\Talent::class),
        'institution' => $faker->word,
        'education_level' => $faker->word,
        'other_education_level' => $faker->word,
        'qualification_field' => $faker->words,
        'start_date_month' => rand(1, 12),
        'start_date_year' => rand(1970, 2000),
        'end_date_month' => rand(1, 12),
        'end_date_year' => rand(1970, 2000),
    ];
});

Below are the tinker commands I ran

$talents = App\Talent::all()
$talents->each( function($talent) { factory(App\Education::class)->create(['talent_id' => $talent->id]); })

The $talents->each( function($talent) { factory(App\Education::class)->create(['talent_id' => $talent->id]); }) is the cause, but I don't understand why